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Water stress (drought and waterlogging) is one highly important factor affecting food security in China. Investigating the effects of soil moisture stress on the morphological and physiological characteristics of maize seedlings is crucial for ensuring food production. The use of spectral monitoring to observe crop phenotypic traits and assess crop health has become a focal point in field crop research. However, studies exploring the contribution of crop phenotypic and physiological data to the Normalized Difference Vegetation Index (NDVI) are still limited. In this study, a 35-day pot experiment was conducted with seven soil moisture gradients: 50%, 60%, 70%, 80% (control group, CK), 90%, 100%, and 110% treatment. In order to investigate the effects of soil moisture stress on seedling phenotypes, antioxidant enzyme activities, and NDVI, an ASD FieldSpec 4 Hi-Res NG portable spectrometer was used to collect spectral data from maize (Zea mays L. B73) leaves. The contributions of maize phenotypic and physiological traits to NDVI were also examined. The results indicated that (1) the 50% and 110% treatments significantly affected maize seedling phenotypes compared to the CK group; (2) the activities of superoxide dismutase (SOD) and peroxidase (POD) in the leaves increased under water stress, while the activities of glutathione peroxidase (GSH-PX) and ascorbate peroxidase (APX) decreased; (3) soil moisture stress (drought and waterlogging) reduced photosynthetic pigments, chlorophyll content (SPAD), and NDVI, with inhibitory effects intensifying as the stress level increased; (4) Redundancy analysis showed that antioxidant enzymes explained 69.87% of the variation in seedling height, leaf area, and NDVI. Soil moisture stress, chlorophyll, and SPAD explained 58.14% of the variation in these parameters. The results demonstrated that maize seedlings were highly sensitive to soil moisture changes, and the SPAD value contributed significantly to NDVI (p < 0.01). This study provides valuable insights for future research in precision agriculture management [ABSTRACT FROM AUTHOR]

The development of a crop production strategy through the use of a crop model represents a crucial method for the assurance of a stable agricultural yield and the subsequent enhancement thereof. There are currently no studies evaluating the suitability of the AquaCrop model for the drip irrigation of Gossypium barbadense in Southern Xinjiang, which is the primary planting region for Gossypium barbadense in China. In order to investigate the performance of the AquaCrop model in simulating the growth of cotton under mulched drip irrigation, the model was locally calibrated and validated according to different irrigation thresholds during a key growth period of two years. The results of the simulation for total soil water (TSW), crop evapotranspiration (ETc), canopy coverage (CC), aboveground biomass (Bio), and seed cotton yield demonstrated a high degree of correlation with the observed data, with a root mean square error (RMSE) of <11.58%. The Bio and yield simulations demonstrated a high degree of concordance with the corresponding measured values, with root mean square error (RMSE) values of 1.23 t ha−1 and 0.15 t ha−1, respectively. However, the predicted yield declined in the verification year, though the prediction error remained below 15%. Furthermore, the estimated evapotranspiration (ETc) value demonstrated a slight degree of overestimation. Generally, the middle and late stages of cotton growth led to an overestimation of the TSW content. However, the prediction error was less than 13.99%. Through the calculation of each performance index of the AquaCrop model, it is found that they are in the acceptable range. In conclusion, the AquaCrop model can be employed as a viable tool for predicting the water response of cotton to drip irrigation under mulched film in Southern Xinjiang. Based on 64 years of historical meteorological data, three years were selected as scenarios for simulation. Principal component analysis (PCA) showed that, in a local wet year in Southern Xinjiang, the irrigation quota was 520 mm, and the irrigation cycle was 6 days/time. In normal years, the irrigation quota was 520 mm, with an irrigation cycle of 6 days/time. In dry years, the irrigation quota was 595 mm, with an irrigation cycle of 10 days/time. This allowed for higher seed cotton yields and irrigation water productivity, as well as the maximization of cotton yields and net revenue in the arid oasis area of Southern Xinjiang. [ABSTRACT FROM AUTHOR]

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Background and Aims: Leaf senescence is accelerated by soil moisture stress during reproductive growth in rainfed paddy rice under drought and in irrigated paddy rice under intermittent irrigation for saving water or mitigating methane emissions. Leaf senescence decreases leaf photosynthetic rate (An) and grain yield. We aimed to elucidate the mechanisms underlying the An decrease under soil moisture stress. Methods: An, leaf content of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), synthesis and degradation of Rubisco and cytokinin flux from roots were compared between plants grown in moisture-deficient soil (DR-plants) and flooded or wet soil (FL- or WE-plants, respectively) during senescence in pot-grown rice (Oryza sativa L.). Results: The decreases in An and Rubisco content were larger in the DR-plants than in the FL-plants. An was closely correlated with Rubisco content during moisture stress treatment. The larger decrease of Rubisco content in the DR-plants was from increased Rubisco degradation rather than decreased synthesis. The amount of cytokinins transported from roots to shoots was smaller in the DR-plants. The application of 6-benzylaminopurine to leaves of the DR-plants suppressed Rubisco degradation. In a wilty mutant with impaired leaf hydraulic conductance, leaf senescence was significantly higher in the DR-plants than in the FL-plants, although leaf water potential of both groups decreased similarly under sunny conditions. Conclusion: The main cause of an An decrease with senescence in rice under soil moisture stress was the decrease of cytokinin flux from roots to shoots and enhanced Rubisco degradation. [ABSTRACT FROM AUTHOR]

Water stress (drought and waterlogging) is one highly important factor affecting food security in China. Investigating the effects of soil moisture stress on the morphological and physiological characteristics of maize seedlings is crucial for ensuring food production. The use of spectral monitoring to observe crop phenotypic traits and assess crop health has become a focal point in field crop research. However, studies exploring the contribution of crop phenotypic and physiological data to the Normalized Difference Vegetation Index (NDVI) are still limited. In this study, a 35-day pot experiment was conducted with seven soil moisture gradients: 50%, 60%, 70%, 80% (control group, CK), 90%, 100%, and 110% treatment. In order to investigate the effects of soil moisture stress on seedling phenotypes, antioxidant enzyme activities, and NDVI, an ASD FieldSpec 4 Hi-Res NG portable spectrometer was used to collect spectral data from maize (Zea mays L. B73) leaves. The contributions of maize phenotypic and physiological traits to NDVI were also examined. The results indicated that (1) the 50% and 110% treatments significantly affected maize seedling phenotypes compared to the CK group; (2) the activities of superoxide dismutase (SOD) and peroxidase (POD) in the leaves increased under water stress, while the activities of glutathione peroxidase (GSH-PX) and ascorbate peroxidase (APX) decreased; (3) soil moisture stress (drought and waterlogging) reduced photosynthetic pigments, chlorophyll content (SPAD), and NDVI, with inhibitory effects intensifying as the stress level increased; (4) Redundancy analysis showed that antioxidant enzymes explained 69.87% of the variation in seedling height, leaf area, and NDVI. Soil moisture stress, chlorophyll, and SPAD explained 58.14% of the variation in these parameters. The results demonstrated that maize seedlings were highly sensitive to soil moisture changes, and the SPAD value contributed significantly to NDVI (p < 0.01). This study provides valuable insights for future research in precision agriculture management

The development of a crop production strategy through the use of a crop model represents a crucial method for the assurance of a stable agricultural yield and the subsequent enhancement thereof. There are currently no studies evaluating the suitability of the AquaCrop model for the drip irrigation of Gossypium barbadense in Southern Xinjiang, which is the primary planting region for Gossypium barbadense in China. In order to investigate the performance of the AquaCrop model in simulating the growth of cotton under mulched drip irrigation, the model was locally calibrated and validated according to different irrigation thresholds during a key growth period of two years. The results of the simulation for total soil water (TSW), crop evapotranspiration (ETc), canopy coverage (CC), aboveground biomass (Bio), and seed cotton yield demonstrated a high degree of correlation with the observed data, with a root mean square error (RMSE) of −1 and 0.15 t ha−1, respectively. However, the predicted yield declined in the verification year, though the prediction error remained below 15%. Furthermore, the estimated evapotranspiration (ETc) value demonstrated a slight degree of overestimation. Generally, the middle and late stages of cotton growth led to an overestimation of the TSW content. However, the prediction error was less than 13.99%. Through the calculation of each performance index of the AquaCrop model, it is found that they are in the acceptable range. In conclusion, the AquaCrop model can be employed as a viable tool for predicting the water response of cotton to drip irrigation under mulched film in Southern Xinjiang. Based on 64 years of historical meteorological data, three years were selected as scenarios for simulation. Principal component analysis (PCA) showed that, in a local wet year in Southern Xinjiang, the irrigation quota was 520 mm, and the irrigation cycle was 6 days/time. In normal years, the irrigation quota was 520 mm, with an irrigation cycle of 6 days/time. In dry years, the irrigation quota was 595 mm, with an irrigation cycle of 10 days/time. This allowed for higher seed cotton yields and irrigation water productivity, as well as the maximization of cotton yields and net revenue in the arid oasis area of Southern Xinjiang.

Tetracentron sinense Oliv. is an endangered relict tree found in south-central China. A low number of seedlings among the natural populations has resulted in the poor regeneration of this species. However, the mechanisms underlying seedling survival and growth remain poorly understood. Leaf functional traits (LFT) likely characterize the growth and development of T. sinense in different ecological environments, playing a crucial role in its adaptive strategies to adversity. In this study, two-factor orthogonal control experiments with two levels of light intensity (L1: 50 % natural light intensity in forest edge; L2: 10 % natural light intensity in understory) and soil moisture content (W1: 30 % moisture content in valley; W2: 15 % moisture content in mountainside) were conducted to analyze the response of the LFT of 7-month-old T. sinense seedlings to different light and soil moisture conditions. With the light intensity decreased, superoxide dismutase activity decreased, and peroxidase activity increased. With a decrease in soil moisture, the contents of chlorophyll (Chl) a, Chl b, Chl t, and soluble sugar increased, and Chl a/b decreased. A decrease in light and soil moisture decreased leaf thickness, leaf dry weight, leaf dry matter content, leaf volume, chloroplast volume, and starch grains, but increased osmophilic grains, the total nitrogen, and phosphorus contents. Moreover, the chloroplast morphology of L2W2 was more complete than that of other treatments. The results showed that the LFT of T. sinense seedlings acted synergistically to adapt to different light and soil moisture conditions, low soil moisture alleviated the effects of shading in T. sinense seedlings, and T. sinense seedlings adopted the “quick investment-return strategy” adaptation strategy under L2W2. Finally, the soil moisture of the mountainside in the natural habitat was favorable to the survival and growth of T. sinense seedlings.

The impact of climate change on agriculture and food production is manifested through alterations in agro-ecological factors. The region of sub-Saharan Africa is particularly susceptible to the effects of climate change and variability, given its reliance on rainfall-dependent agriculture and inadequate adaptive capabilities. The objective of this study was to analysis of the characterization of climate change and its impacts on smallholder farmers in eastern Ethiopia. Historical daily rainfall, maximum and minimum temperature in 1991–2021 years of 12 weather station were collected from National Meteorological Institute of Ethiopia and NASA/POWER. Data quality control, trend test and outlier detection test were used. Climate characterization (onset, cessation, LGS and Dry/wet spell length) and precipitation concentration index were examined. The earliest, and latest start of rainy season in Kombolcha and Haramaya were 81DOY (March 21) and 225DOY (August 13) within mean 130DOY and 125DOY, respectively. In study area the minimum and maximum length of growing period of was recorded in Chinakesen and Haramaya by the values of 32DOY and 253DOY (Days of the year) respectively. In this arid and semi-arid areas, growing period was recorded under the short season crop maturity while long cropping season maturity does no satisfy crop water requirement due to moisture stress. The coefficient of variation of length of growing season from Mieso and Chinakesen were 36.2% and 47.9% which implies that the areas were highly vulnerable to climate extreme events of drought. Length of growing season (LGS) of Gemechis district was decreasing by a factor −2.533 shows highly significant at alpha value of 0.05 confidence level. Dry spell length probability occurrence of 5 days during the main cropping rainy season is significantly very high. The 30 years of data record suggests that a 29–48% precipitation concentration index of kiremt (JJAS) and belg (FMAM) seasonal rainfall which are demonstrating irregular precipitation. kiremt (JJAS) rainfall trend tests of Babile, Kurfa chale and Mieso districts were increasing by a factor of 2.016, 2.043 and 2.117, respectively and statistically significant at 95% confidence level, in the time period of 1991–2021 years. If furtherstudy will be examined climate extreme indices and adaptation strategies designed to simulate the impacts and variability of climate change in the study area.

Plants produce variety of secondary metabolites in response to stress. The study aimed to evaluate the soil moisture stress on oil content & composition of German chamomile conducted in, 2020 and 2021 at CSIR-Central Institute of Medicinal and Aromatic Plant, Research Centre, Pantnagar, Uttarakhand, India. The treatments were T1 (just before irrigation), T2 (24 h after irrigation), T3 (72 h after irrigation), T4 (120 h after irrigation), and T5 (168 h after irrigation). Results showed that maximum oil content (0.26 & 0.57 ml/100g) was found in fresh and dry flowers, respectively of T2 & oil content decreased as the days to irrigation increased. GC results showed that the percentage of major compounds was lowest (74.02%) while maximum in acute drought conditions i.e. before irrigation (92.12%). Results suggest that soil moisture stress reduces the oil content however, the quality of oil is enhanced due to increased production of secondary metabolites. [ABSTRACT FROM AUTHOR]

Leaf chlorophyll pigment and macronutrient concentrations were quantified for four willow species (Salix cordata (COR), S. discolor (DIS), S. eriocephala (ERI) and S. interior (INT)) while growing under 2 × 2 factorial of ambient and elevated CO2 and well-watered and drought-stressed soil moisture treatments (Expt. 1). After the first year, we saw no difference in stem biomass between CO2 treatments. In the following year, a second experiment was conducted on a subset of well-watered willows as a 2 × 2 factorial of atmospheric CO2 and soil fertilization (FERT). For both years of Expt. 1, chlorophyll a, b, a + b (TCC) and carotenoids (CAR) significantly downregulated in response to elevated CO2 (eCO2) and upregulated in response to drought (DRT). In Expt. 2, FERT mitigated CO2 downregulation of TCC and CAR, and upregulated TCC and CAR. Across species, ERI had the greatest pigment concentrations followed by either COR or DIS. Except for one case, INT had the lowest pigment concentrations. A significant species x FERT interaction was due to magnitude effects. The CHLa:b ratio was not affected by CO2 or DRT but did increase in response to FERT. INT had the greatest CHLa:b ratio followed by DIS, then either ERI or COR. In the second year, TCC:CAR ratio decreased in response to eCO2 and increased in response to DRT and FERT. In Expt. 1, leaf N was the only nutrient to significantly downregulate in response to eCO2; whereas all other nutrient levels remained unchanged. In response to DRT, leaf N and Mg upregulated; whereas leaf P, K, and Ca were downregulated. In response to eCO2 in Expt. 2, again only leaf N downregulated; whereas all other nutrients remained unchanged. All leaf nutrients upregulated in response to FERT. Of the four species, INT had the greatest leaf N and K, and the lowest Ca. Species variation was important, but so to was clonal variation in response to change. Indeed, INT leaf chlorophyll and macronutrients are significantly different or segregated from the other three willow species and this may be related to the evolutionary origins of INT, and other species of the taxonomic section Longifoliae, in the arid southwest USA and Mexico. Furthermore, under low nutrient conditions, it may be necessary to fertilize the plants to see a biomass response to eCO2. [ABSTRACT FROM AUTHOR]

In the semi-arid and arid environments of Sub-Sharan Africa, forage availability throughout the year is insufficient and highly limited during the dry seasons due to limited precipitation. Thus, the identification of drought stress-tolerant forage cultivars is one of the main activities in forage development programs. In this study, Napier grass (Cenchrus purpureus), an important forage crop in Eastern and Central Africa that is broadly adapted to produce across tropical environments, was evaluated for its water use efficiency and production performance under field drought stress conditions. Eighty-four Napier grass genotypes were evaluated for their drought stress tolerance from 2018 to 2020 using agro-morphological and feed quality traits under two soil moisture stress regimes during the dry season, i.e., moderate (MWS) and severe (SWS) water stress conditions, and under rainfed conditions in the wet season (wet). Overall, the results indicated the existence of genotype variation for the traits studied. In general, the growth and productivity of the genotypes declined under SWS compared to MWS conditions. High biomass-yielding genotypes with enhanced WUE were consistently observed across harvests in each soil moisture stress regime. In addition, the top biomass-yielding genotypes produced the highest annual crude protein yield, indicating the possibility of developing high-feed-quality Napier grass genotypes for drought stress environments. [ABSTRACT FROM AUTHOR]

Evapotranspiration (ET) is a critical component of the water, carbon and energy cycles of the land surface. Remote sensing-based models provide the possibility of mapping ET from field to regional and even global scales. A key boundary condition of the Two-Source Energy Balance (TSEB) model for computing ET is land surface temperature (LST). The proposed modification to TSEB is to use a combination of near surface soil moisture (SM) derived by microwave and LST as dual boundary conditions along with a more physically-based transpiration formulation for computing ET. Both TSEB and TSEB-SM were applied to an irrigated agricultural area with surrounding semi-arid sparse natural vegetation. In general, TSEB-SM model performance when compared to measured fluxes was similar to the TSEB model. However, the TSEB-SM model computed more reliable estimates of LE under dry soil surface/low vegetation cover conditions, primarily in the arid and semiarid natural ecosystems surrounding the irrigated agricultural area. These comparisons indicate that TSEB-SM may provide more reliable flux estimation and ET partitioning over sparsely vegetated areas compared to the traditional formulations used in TSEB. With reliable microwave remote sensing of soil moisture, TSEB-SM has potential for ET monitoring in both natural and agricultural landscapes.

Assimilation to the internal CO2 (ACi) response curve and gas exchange parameters were quantified for four North American willows ((Salix cordata (COR), S. discolor (DIS), S. eriocephala (ERI), and S. interior (INT)) grown in a 2 × 2 factorial of atmospheric CO2 and soil moisture treatments to see how they would respond to climate change factors. After the first year of greenhouse growth under said treatments, we saw no difference in the aboveground stem biomass between CO2 treatments. Thus, in the second year, a second experiment on a subset of well-watered, coppiced willows was conducted in a 2 × 2 factorial of atmospheric CO2 and soil fertilization (FERT) treatments. In both experiments, the maximum rate of carboxylation (Vcmax) significantly declined for all four species in response to elevated CO2 (eCO2). In response to a drought treatment (DRT), Vcmax declined, except for INT, which increased Vcmax. In both experiments, INT had the greatest Vcmax, maximum rate of electron transport (Jmax), and triose phosphate utilization, followed by COR and ERI, with DIS having the lowest values. FERT resulted in a strong increase in assimilation (A) and stomatal conductance (Gwv) by 92 and 119%, respectively. Gwv is the primary driver and A is a minor driver of water use efficiency (WUE) under DRT. FERT mitigated the Vcmax and A downregulation in eCO2, but eCO2 did not mitigate the DRT downregulation effect. Differences between INT and the other three willows in a number of adaptive traits and responses related to drought may reflect the evolutionary origins of INT and the taxonomic group Longifoliae in the arid southwest USA and Mexico. [ABSTRACT FROM AUTHOR]

Key message: Large differences were detected between genera and among species in chlorophyll pigment and macronutrient concentrations. Pines have greater variances than spruces and showed less downregulation of chlorophyll pigment concentrations than spruces in response to eCO2 and DRT. There was strong genetic control of chlorophyll pigments and most macronutrients. Chlorophyll pigment and needle macronutrient concentrations were quantified for eight tree species in two commercially important genera, Pinus and Picea grown in a 2 × 2 factorial of atmospheric CO2 (370 and 740 ppm) and soil moisture stress (− 0.1 to − 0.5 and − 0.7 to − 1.0 MPa) treatments. Four of the pines and three of the spruces are native to eastern North America, while a fourth spruce, Norway spruce (NS: Picea abies), is from Europe but has been widely used for reforestation in northeastern North America. Overall, spruces had significantly greater chlorophyll a, b, (CHLa, CHLb), and total chlorophyll concentration (TCC) and carotenoid concentration (CAR) than pines. Ambient CO2 (aCO2) had significantly greater TCC than in response to elevated CO2 (eCO2), and TCC and CAR was significantly downregulated more in spruces than in pines in response to eCO2. Pines had equal or greater TCC and CAR in response to drought treatment (DRT) than well-watered treatment, whereas spruces had significantly lower values in response to DRT. Needle N, P and Ca concentrations were greater for spruces than pines. Needle N concentrations declined in response to both eCO2 and DRT. Needle P increased in response to eCO2 but declined in response to DRT. Using total biomass as a covariate, needle N showed no response in pines; whereas spruces showed a slight positive response to increasing total biomass. Covariate analysis showed that TCC had a significant positive relationship to needle N and Mg, with greater TCC in spruces than in pines for a given needle N. Photosynthetic quantum efficiency (QE), derived from light response curves, had a significant positive relationship to TCC that was greater in pines than in spruces for a given TCC. Photosynthetic light convexity had a significant positive relationship to TCC that was also greater in pines than in spruces for a given TCC, indicating a sharper curvature compared to a more progressive curve for spruce. Pine species have greater variances than spruce species. While Pinus strobus (white pine, subgenus Strobus) stands out as having greater chlorophyll and nutrient concentrations than the other three pines (subgenus Pinus). Overall, pines showed less downregulation of chlorophyll pigment concentrations than spruces in response to eCO2 and DRT. There was strong genetic control for chlorophyll pigments and most macronutrients. [ABSTRACT FROM AUTHOR]

Leaf chlorophyll pigment and macronutrient concentrations were quantified for four willow species (Salix cordata (COR), S. discolor (DIS), S. eriocephala (ERI) and S. interior (INT)) while growing under 2 × 2 factorial of ambient and elevated CO2 and well-watered and drought-stressed soil moisture treatments (Expt. 1). After the first year, we saw no difference in stem biomass between CO2 treatments. In the following year, a second experiment was conducted on a subset of well-watered willows as a 2 × 2 factorial of atmospheric CO2 and soil fertilization (FERT). For both years of Expt. 1, chlorophyll a, b, a + b (TCC) and carotenoids (CAR) significantly downregulated in response to elevated CO2 (eCO2) and upregulated in response to drought (DRT). In Expt. 2, FERT mitigated CO2 downregulation of TCC and CAR, and upregulated TCC and CAR. Across species, ERI had the greatest pigment concentrations followed by either COR or DIS. Except for one case, INT had the lowest pigment concentrations. A significant species x FERT interaction was due to magnitude effects. The CHLa:b ratio was not affected by CO2 or DRT but did increase in response to FERT. INT had the greatest CHLa:b ratio followed by DIS, then either ERI or COR. In the second year, TCC:CAR ratio decreased in response to eCO2 and increased in response to DRT and FERT. In Expt. 1, leaf N was the only nutrient to significantly downregulate in response to eCO2; whereas all other nutrient levels remained unchanged. In response to DRT, leaf N and Mg upregulated; whereas leaf P, K, and Ca were downregulated. In response to eCO2 in Expt. 2, again only leaf N downregulated; whereas all other nutrients remained unchanged. All leaf nutrients upregulated in response to FERT. Of the four species, INT had the greatest leaf N and K, and the lowest Ca. Species variation was important, but so to was clonal variation in response to change. Indeed, INT leaf chlorophyll and macronutrients are significantly different or segregated from the other three willow species and this may be related to the evolutionary origins of INT, and other species of the taxonomic section Longifoliae, in the arid southwest USA and Mexico. Furthermore, under low nutrient conditions, it may be necessary to fertilize the plants to see a biomass response to eCO2.

In the semi-arid and arid environments of Sub-Sharan Africa, forage availability throughout the year is insufficient and highly limited during the dry seasons due to limited precipitation. Thus, the identification of drought stress-tolerant forage cultivars is one of the main activities in forage development programs. In this study, Napier grass (Cenchrus purpureus), an important forage crop in Eastern and Central Africa that is broadly adapted to produce across tropical environments, was evaluated for its water use efficiency and production performance under field drought stress conditions. Eighty-four Napier grass genotypes were evaluated for their drought stress tolerance from 2018 to 2020 using agro-morphological and feed quality traits under two soil moisture stress regimes during the dry season, i.e., moderate (MWS) and severe (SWS) water stress conditions, and under rainfed conditions in the wet season (wet). Overall, the results indicated the existence of genotype variation for the traits studied. In general, the growth and productivity of the genotypes declined under SWS compared to MWS conditions. High biomass-yielding genotypes with enhanced WUE were consistently observed across harvests in each soil moisture stress regime. In addition, the top biomass-yielding genotypes produced the highest annual crude protein yield, indicating the possibility of developing high-feed-quality Napier grass genotypes for drought stress environments.

In the human diet, particularly for most of the vegetarian population, mungbean (Vigna radiata L. Wilczek) is an inexpensive and environmentally friendly source of protein. Being a short-duration crop, mungbean fits well into different cropping systems dominated by staple food crops such as rice and wheat. Hence, knowing the growth and production pattern of this important legume under various soil moisture conditions gains paramount significance. Toward that end, 24 elite mungbean genotypes were grown with and without water stress for 25 days in a controlled environment. Top view and side view (two) images of all genotypes captured by a high-resolution camera installed in the high-throughput phenomics were analyzed to extract the pertinent parameters associated with plant features. We tested eight different multivariate models employing machine learning algorithms to predict fresh biomass from different features extracted from the images of diverse genotypes in the presence and absence of soil moisture stress. Based on the mean absolute error (MAE), root mean square error (RMSE), and R squared (R 2) values, which are used to assess the precision of a model, the partial least square (PLS) method among the eight models was selected for the prediction of biomass. The predicted biomass was used to compute the plant growth rates and water-use indices, which were found to be highly promising surrogate traits as they could differentiate the response of genotypes to soil moisture stress more effectively. To the best of our knowledge, this is perhaps the first report stating the use of a phenomics method as a promising tool for assessing growth rates and also the productive use of water in mungbean crop. [ABSTRACT FROM AUTHOR]

Global water crisis, resulting from climate change, has become a prime concern for agricultural production. Our objectives were to determine the impact of puddling and soil compactionon drought tolerance, metabolism and antioxidative enzymes affecting growth of hybrid rice (Oryza sativa L.) under drought conditions. Accordingly, an experiment with three treatments, viz., puddled, compact, and control soils was conducted in pots using a completely randomized design with three replications. Both puddling and soil compaction reduced the adverse effects of drought on physiological traits. The positive effects of water stagnation because of physical modifications of soil, on drought tolerance traits and antioxidative enzymes during water stress, caused 1.2 to 2-fold increase in penetration resistance of physically modified soils and concomitantly reduced 3 to 6-fold water infiltration rate thereof. Puddling and soil compaction enabled plants maintain higher water potential than the control plants under drought conditions. Such plant conditions in puddled and compact soils caused low levels of proline and sugar, followed by higher levels of starch and protein than the control plants. Drought increased superoxide dismutase activity 2 to 2.4-fold, catalase 2 to 2.2-fold, ascorbate peroxidase 1.7 to 2-fold, and lipid peroxidase 2.3 to 3.6-fold. Adaptation to drought was apparently attributable to the cross-talk of drought event with plant metabolism, giving rise to the evolution of protective metabolic strategies. Thus, the increased water availability, through decreased water infiltration caused by puddling and soil compaction, is an important agronomic intervention for the maintenance of physiological activities andgrowth of rice under drought conditions. [ABSTRACT FROM AUTHOR]

The present era is witnessing a serious water crisis affecting rice (Oryza sativa) productivity adversely. Therefore, with the objective of minimizing crop failure under limited water supply the effects of organic manures were compared with inorganic fertilizer for changes in soil physical characteristics, morpho-physiological traits and drought resistance of hybrid rice NDRH-2. Accordingly, one level each of green manure and compost (7.5 t ha−1) was applied supplemented with chemical fertilizers to bring them nutritionally at par with inorganic fertilizer treatment. Organic manures minimized the adverse effect of drought on plant height during a 10-day soil-drying cycle. Organically fertilized treatments enhanced plant sustenance by 4-7 days during drought compared with that fertilized inorganically. Sustenance enhancement was probably due to increased soil moisture-holding capacity [26% to 27.4% in organically fertilized soil (OFS) against 22.2% in inorganically fertilized soil (IFS)] because of decreased soil bulk density (1.20g mL−1 OFS against 1.42 IFS) and soil penetration resistance (500 to 560 kPa OFS against 800 kPa IFS). The organic manures significantly increased leaf water potential (−16 to −18.5 bars OFS against −25 bars IFS), relative water content (84 to 85% OFS against 78% IFS), cell viability (OD 0.290 to 0.352 OFS against 0.165 IFS), membrane stability (83 to 87% OFS against 75%IFS), chlorophyll (10.06 mg g−1 dry weight OFS against 9.42 IFS) and reduced leaf injury (score 3 to 4 OFS against 5 IFS) causedby drought. Hence, farmers living in drought-prone regions, are advised to practice organic farming using organic manures for a successful rice crop in event of scanty rainfall. [ABSTRACT FROM AUTHOR]

An experiment was conducted during 2015–2016 to 2017–2018 at UP Council of Sugarcane Research, Shahjahanpur. Ten promising sugarcane varieties, viz. CoS 12232, CoS 14232, CoS 06279, CoS 10231, CoS 13231, Co 0238, CoS 09232, CoS 08276, CoS 08279 and CoSe 01434, were used for the evaluation of drought-tolerant varieties suitable for planting under water stress condition. Two moisture levels, normal (50 ASM) and deficient (20 ASM), were maintained during pre-monsoon period. Stomatal behavior was studied. Results revealed that all the varieties were adversely affected due to deficient moisture level. Under deficient moisture, varieties CoS 12232, CoS 14232 and CoS 06279 expressed higher total chlorophyll. These varieties showed the minimum rate of transpiration along with maximum stomatal diffusive resistance and leaf water potential under water stress. These varieties also showed a significant reduction in shoot height, leaf area of the first open leaf, shoot population, number of millable canes and cane yield (below 10%) under low moisture levels as compared with other tested varieties. Due to water stress, sucrose content was not affected significantly. Conclusively, varieties CoS 12232, CoS 14232 and CoS 06279 were found suitable for planting under deficient moisture condition. [ABSTRACT FROM AUTHOR]

Highlights • Four pines and four spruces in a 2 × 2 factorial of CO 2 and soil moisture. • Overall, pines respond better to eCO 2 and soil moisture stress. • Shade-tolerant spruces perform better in eCO 2 than shade-intolerant spruces. • Greater the mass, greater the response to eCO 2 and soil moisture. • Supports shift toward increased use of pines in NE N. America. Abstract Growth, components of growth, and biomass allocation were quantified for eight species in two commercially important genera, Pinus and Picea , grown in a 2 × 2 factorial of atmospheric CO 2 and soil moisture stress. Four of the pines and three of the spruces are native to eastern North America; a fourth spruce, Norway spruce (NS: P. abies), is native to Europe but is used for reforestation in northeastern North America. Height, basal diameter (BD), and total biomass response of pines were often more than two times greater than that of spruces under elevated CO 2 (eCO 2). A significant species × CO 2 interaction for total biomass was a result of species' differential response to eCO 2 : Pinus rigida had the greatest biomass stimulation (59%), followed by P. resinosa (39%), P. strobus (26%), and P. banksiana (19%). Among spruces, Picea glauca showed the greatest response (30%), and P. mariana the least response under eCO 2 (5%). Overall, soil moisture stress reduced total productivity by 12%. Most pines did have greater growth under moisture stress, and NS and BS grew well. Percent needle mass was lower under eCO 2 , but this was not due directly to eCO 2 but to ontological changes. Controlling for size, pines had 20% greater needle biomass than spruces, while having a negative relationship to total biomass. A comparison of total biomass under eCO 2 in relation to aCO 2 by species showed that overall, the greater the species mass, the greater the mass gain under eCO 2, and the greater the mass loss under drought conditions. In addition, our results for spruces lend strong support to the theory that late-successional species have greater growth response under eCO 2 than early to mid-successional species. A diverse portfolio of tree species for artificial reforestation would help forest management adapt to the many uncertainties over future environments and markets, but our results on responses in spruces and pines to eCO 2 and soil moisture stress support a shift toward increased use of pines in forest management and artificial reforestation. [ABSTRACT FROM AUTHOR]

The impact of climate change on agriculture and food production is manifested through alterations in agro-ecological factors. The region of sub-Saharan Africa is particularly susceptible to the effects of climate change and variability, given its reliance on rainfall-dependent agriculture and inadequate adaptive capabilities. The objective of this study was to analysis of the characterization of climate change and its impacts on smallholder farmers in eastern Ethiopia. Historical daily rainfall, maximum and minimum temperature in 1991-2021 years of 12 weather station were collected from National Meteorological Institute of Ethiopia and NASA/POWER. Data quality control, trend test and outlier detection test were used. Climate characterization (onset, cessation, LGS and Dry/wet spell length) and precipitation concentration index were examined. The earliest, and latest start of rainy season in Kombolcha and Haramaya were 81DOY (March 21) and 225DOY (August 13) within mean 130DOY and 125DOY, respectively. In study area the minimum and maximum length of growing period of was recorded in Chinakesen and Haramaya by the values of 32DOY and 253DOY (Days of the year) respectively. In this arid and semi-arid areas, growing period was recorded under the short season crop maturity while long cropping season maturity does no satisfy crop water requirement due to moisture stress. The coefficient of variation of length of growing season from Mieso and Chinakesen were 36.2% and 47.9% which implies that the areas were highly vulnerable to climate extreme events of drought. Length of growing season (LGS) of Gemechis district was decreasing by a factor -2.533 shows highly significant at alpha value of 0.05 confidence level. Dry spell length probability occurrence of 5 days during the main cropping rainy season is significantly very high. The 30 years of data record suggests that a 29-48% precipitation concentration index of kiremt (JJAS) and belg (FMAM) seasonal rainfall which are demonstrating irregular precipitation. kiremt (JJAS) rainfall trend tests of Babile, Kurfa chale and Mieso districts were increasing by a factor of 2.016, 2.043 and 2.117, respectively and statistically significant at 95% confidence level, in the time period of 1991-2021 years. If furtherstudy will be examined climate extreme indices and adaptation strategies designed to simulate the impacts and variability of climate change in the study area., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Author.)

Extreme climate events (ECEs) such as drought, frost risk and heat stress cause significant economic losses in Australia. The risk posed by ECEs in the wheat production systems of Australia could be better managed through the identification of safe flowering (SFW) and optimal time of sowing (TOS) windows. To address this issue, three locations (Narrabri, Roseworthy and Merredin), three cultivars (Suntop and Gregory for Narrabri, Mace for both Roseworthy and Merredin) and 20 TOS at 1-week intervals between 1 April and 12 August for the period from 1957 to 2007 were evaluated using the Agricultural Production System sIMulator (APSIM)-Wheat model. Simulation results show that (1) the average frequency of frost events decreased with TOS from 8 to 0 days (d) across the four cases (the combination of locations and cultivars), (2) the average frequency of heat stress events increased with TOS across all cases from 0 to 10 d, (3) soil moisture stress (SMS) increased with earlier TOS before reaching a plateau and then slightly decreasing for Suntop and Gregory at Narrabri and Mace at Roseworthy while SMS increased with TOS for Mace at Merredin from 0.1 to 0.8, (4) Mace at Merredin had the earliest and widest SFW (216-260) while Mace at Roseworthy had latest SFW (257-280), (5) frost risk and heat stress determine SFW at wetter sites (i.e. Narrabri and Roseworthy) while frost risk and SMS determine SFW at drier site (i.e. Merredin) and (6) the optimal TOS (window) to maximise wheat yield are 6-20 May, 13-27 May and 15 April at Narrabri, Roseworthy and Merredin, respectively. These findings provide important and specific information for wheat growers about the management of ECE risk on farm. Furthermore, the coupling of the APSIM crop models with state-of-the-art seasonal and intra-seasonal climate forecast information provides an important tool for improved management of the risk of ECEs in economically important cropping industries in the foreseeable future. [ABSTRACT FROM AUTHOR]

Soil moisture stress seriously limits the growth and development of tea plants ( Camellia sinensis ), thus affecting crop yield and quality. Soil moisture reduction generally affects accumulation of tea secondary metabolites. To elucidate the variations in plant genotype response to abiotic stress during depleting soil moisture stress and changes in biochemical constituents of green leaf which determines the quality of black tea was investigated. An experiment was conducted at UPASI Tea Research Foundation Tea Research Institute, Distinctiveness-Uniformity-Stability center with drought tolerant clones namely UPASI-2, UPASI-6, UPASI-9, ATK-1, TRI-2025 and drought susceptible clones UPASI-3, UPASI-8, UPASI-17, TRF-1 of same age. Green leaves were collected from each plot was subjected to HPLC analysis for dihydroxyflavan-3-ols, trihydroxyflavon-3-ols and caffeine, and the results were statistically analyzed. The study indicated that the levels of total polyphenols, individual catechins, reducing sugars, amino acids and total lipids were significantly different at P ≤ .05 among the treatments. Caffeine level increased (P ≤ .05) with decrease in soil moisture for all the clones. Principal component analysis and hierarchical cluster analysis revealed differences between tea cultivars with respect to their quality and tolerance. Our study further indicated that the tolerant clones were able to accumulate higher levels of bio constituents during soil moisture stress than the susceptible ones. Quality of green tea leaf precursors is directly influenced by the soil moisture availability and is varietal dependent. This could be an important tool for the assessment of clonal performance and drought tolerance in tea cultivars. [ABSTRACT FROM AUTHOR]

A field experiment was conducted during January 2012 to March 2014. Five fodder cowpea varieties (V1- UPC 618, V2-UPC - 622, V3- Bundel Lobia-1, V4 - COFC - 8 and V5- CO-5) were evaluated for their drought tolerance under four soil moisture stress levels (M1- pre sowing irrigation + lifesaving irrigation, M2- pre sowing irrigation + irrigation at IW/CPE ratio of 0.4, M3- pre sowing irrigation + irrigation at IW/CPE ratio of 0.6 and M4-pre sowing irrigation + irrigation at IW/CPE ratio of 0.8). The investigation was conducted as two separate experiments, one in open and other in shade. The experiments were laid out in split plot design with four replications. Observations on growth characters such as plant height, number of branches and leaf stem ratio were recorded. The results revealed that plant height and number of branches were maximum at irrigation at IW/CPE ratio of 0.8 both in open and shade. Among the varieties, COFC - 8 recorded maximum plant height and number of branches at all irrigation levels in open and partial shade. [ABSTRACT FROM AUTHOR]

The article presents an evaluation of advanced potato clones in arid zone in Rajasthan, India for drought tolerance. It mentions the perception of potato growers of heat and drought tolerant varieties as potent tool to tackle the impending threat of climate change and global warming. The efforts to breed and screen potato clones for adaptation to adverse agro-ecologies are also outlined.

A procedure to determine soil moisture threshold (θ *), cover coefficient ( k), and parameters of soil moisture stress function ( k) is proposed in this study. These coefficients can be further applied to estimate daily actual evapotranspiration in a hydrological model. Two soil moisture stress functions are used to describe k. One of the functions is proposed by this study, which assumes moisture stress is inversely proportional to matric potential described by van Genuchten retention curve. The procedure is applied to identify the coefficients for three kinds of reference potential evapotranspiration based on soil moisture monitoring. Soil moisture was measured by Watermark soil moisture sensors. These sensors were tested in a laboratory to establish the relationship between soil moisture and recorded tensor. Then, these sensors were installed in an experimental forest watershed. The verification study shows that the calibrated coefficients can provide reasonable estimate of actual evapotranspiration. The R = 0.85 for using the Penman-Montieth equation for tall maize along with k = 1.81 can be obtained for the validation period with soil moisture stress. Besides, the results also indicate the proposed soil moisture stress function can have better performance on estimating daily actual evapotranspiration at early stage of a dry period. The proposed procedure and soil moisture stress functions can be successfully applied to estimate daily evapotranspiration when soil moisture is known. However, their performance in a hydrological model requires further study, since a hydrological model can only provide estimated soil moisture. [ABSTRACT FROM AUTHOR]

Four varieties of grape namely Flame Seedless, Thompson Seedless, Sharad Seedless and Tas-A-Ganesh were subjected to different levels of moisture stress to study their physiological response. Stress was imposed for 14 days by withholding irrigation. Observations on relative water content, leaf water potential, leaf osmotic potential and gas exchange parameters like photosynthetic rate, transpiration rate, stomatal conductance and water use efficiency (WUE) were recorded. None of the varieties could survive for 14 days without irrigation (100% stress). Flame Seedless and Thompson Seedless at 50% moisture stress maintained higher turgidity as indicated by lesser reduction in relative water content and water potential attributed to better osmotic adjustment. Marginal reduction in photosynthesis and greater reduction in transpiration rate in the variety Flame Seedless may have resulted in higher WUE under moisture stress. Higher photosynthetic rate, lower transpiration rate, higher water relation parameters and high WUE in Flame Seedless under soil moisture stress indicated its better tolerance to drought.

In the arid and semi-arid regions, soil moisture deficiency largely limits sustainable crop production. In the Nigerian dry Savanna (Northern Guinea savanna, arid and semi-arid zones), dry spells commonly occur between June and July, often lasts beyond three weeks. Rainfall is unevenly distributed and results in insufficient soil moisture for crop production. Soils at the uplands are commonly sandy loam to loamy sand at the surface horizons, have inherently poor fertility status, poor moisture retention capacity and rapidly degrade due to sheet erosion, continuous cultivation and overgrazing. The study on cross banding of ridges to conserve moisture and use of boron in association with nitrogen, and without boron was therefore conducted in Sabon Gari Garu areas in Katsina State, in the dry savanna of Nigeria during the 2007 and 2008 cotton cropping seasons. Data obtained were statistically analyzed. Results show that treatment with tied ridges + NPK + boron (415.70 kg ha−1 and 312.47 kg ha−1 cotton in respective years) resulted in significant higher cotton lint yields in 2007 and 2008 than NPK + boron treatments (245.20 kg ha−1 and 255.16 kg ha−1 cotton in 2007 and 2008, respectively). Cross banding of ridges is recommended for farmers to conserve soil moisture and application of NPK + boron fertilizers. [ABSTRACT FROM AUTHOR]

Abstract: Switchgrass (Panicum virgatum L.), a native of eastern and central North America, is a leading candidate as a dedicated biofuel feedstock in the US due to its broad adaptability, rapid growth rate, and ability to grow in low production soils. To begin to characterize the important agronomic and ecological traits related to environmental tolerance of switchgrass, we evaluated fitness under stressful growing conditions. We assessed the germination, establishment, performance, and reproductive potential of four common accessions, both upland and lowland ecotypes, at various levels of soil moisture availability (moisture deficit to flooded) in the greenhouse. Seeds emerged and established (55–90% survival) under all soil moisture conditions (−0.3MPa to flooded). Transplants of lowland ecotypes performed as well in flooded conditions as in field capacity controls, though flooding reduced performance of upland ecotypes. Drought treatments (−4.0 and −11.0MPa) reduced tiller length and number, leaf area, and biomass production by up to 80%. However, once established, all plants survived at −4.0MPa and had the same proportion of tillers in flower as at field capacity. The ability of switchgrass to germinate, establish, and flower in low moisture and flooded conditions, particularly lowland ecotypes, may increase the range of environments suitable for biofuel cultivation, and can serve as a baseline for further ecological studies and genetic improvement. [Copyright &y& Elsevier]

We examined the effects of atmospheric vapor pressure deficit (VPD) and soil moisture stress (SMS) on leaf- and stand-level CO2 exchange in model 3-year-old coppiced cottonwood ( Populus deltoides Bartr.) plantations using the large-scale, controlled environments of the Biosphere 2 Laboratory. A short-term experiment was imposed on top of continuing, long-term CO2 treatments (43 and 120 Pa), at the end of the growing season. For the experiment, the plantations were exposed for 6–14 days to low and high VPD (0.6 and 2.5 kPa) at low and high volumetric soil moisture contents (25–39%). When system gross CO2 assimilation was corrected for leaf area, system net CO2 exchange (SNCE), integrated daily SNCE, and system respiration increased in response to elevated CO2. The increases were mainly as a result of the larger leaf area developed during growth at high CO2, before the short-term experiment; the observed decline in responses to SMS and high VPD treatments was partly because of leaf area reduction. Elevated CO2 ameliorated the gas exchange consequences of water stress at the stand level, in all treatments. The initial slope of light response curves of stand photosynthesis (efficiency of light use by the stand) increased in response to elevated CO2 under all treatments. Leaf-level net CO2 assimilation rate and apparent quantum efficiency were consistently higher, and stomatal conductance and transpiration were significantly lower, under high CO2 in all soil moisture and VPD combinations (except for conductance and transpiration in high soil moisture, low VPD). Comparisons of leaf- and stand-level gross CO2 exchange indicated that the limitation of assimilation because of canopy light environment (in well-irrigated stands; ratio of leaf : stand=3.2–3.5) switched to a predominantly individual leaf limitation (because of stomatal closure) in response to water stress (leaf : stand=0.8–1.3). These observations enabled a good prediction of whole stand assimilation from leaf-level data under water-stressed conditions; the predictive ability was less under well-watered conditions. The data also demonstrated the need for a better understanding of the relationship between leaf water potential, leaf abscission, and stand LAI. [ABSTRACT FROM AUTHOR]

Inheritance of water use and transpiration efficiency was studied in diallel F1 hybrids from six cultivars of T. durum, selected for their different responses to drought stress. Plants were grown in 10 l pots at optimal (control) and low soil moisture levels in the glasshouse. GCA and SCA effects were significant at both soil moisture levels. Results demonstrated that evapotranspiration (ETE) and transpiration efficiency (TE) were under additive and dominant gene control. Interactions of GCA and SCA with moisture levels were also highly significant. GCA effects were the major components of the genetic variance of the biological and generative measures of ETE and TE. Narrow sense heritabilities for both ETE and TE based on grain yield were higher at the soil stress moisture level. Heritability estimates of ETE and TE based on the total biological yield, however, declined under the lower soil moisture level. Measures of ETE and TE showed significantly high and positive genotypic and phenotypic correlations among them as well as with grain yield and harvest index. In most cases, genotypic correlations were higher than phenotypic correlations. The results suggest that selection for high ETE and TE in terms of grain yield should be undertaken under both stress and optimal conditions. Selection in early segregating generations may lead to effective identification of desirable recombinants. [ABSTRACT FROM AUTHOR]

Response to urea fertilizer with drip irrigation was tested and compared with conventional furrow irrigation for 2 years (1995 and 1996) at the Research Farm of Water Management Project, Mahatma Phule Agricultural University, Rahuri (Maharashtra), India. Application of nitrogen through the drip irrigation in ten equal splits at 8-days interval saved 20–40% nitrogen as compared to the furrow irrigation when nitrogen was applied in two equal splits (at planting and 1 month thereafter). Similarly, 3.7–12.5% higher fruit yield with 31–37% saving of water was obtained in the drip system. Water use efficiency in drip irrigation, on an average over nitrogen level was 68 and 77% higher over surface irrigation in 1995 and 1996, respectively. At 120 kgN ha−1, maximum tomato fruit yield of 27.4 and 35.2 t ha−1 in 2 years was recorded. Total nitrogen uptake in drip irrigation was 8–11% higher than that of furrow irrigation. At the highest level of applied nitrogen (120 kgN ha−1), total average N uptake of 2 years was 64.5 (1995) and 104.7 kg ha−1 (1996). The apparent N recovery was 82.5% at 48 kgN ha−1 in comparison with 47.9% at 120 kgN ha−1 during 1996. Stomatal resistance was higher in furrow irrigation than that of drip system at various plant height. Lower leaf had less resistance than upper leaf irrespective of irrigation methods. [Copyright &y& Elsevier]

In the Western Cape region of South Africa, mild weather during the late season is conducive to continued high rates of photosynthesis in apple trees. During the post-harvest period, both stressful environmental conditions and altered tree carbohydrate demand (sink strength) may influence stomatal function and thus gas exchange and tree water requirements. In this study we investigated the interactive effects of the main atmospheric determinants of stomatal conductance (light, leaf temperature, leaf-to-air vapour pressure deficit (VPD)) in response to fruit removal at harvest and soil moisture stress after harvest (cessation of irrigation). An 8-year-old ‘Braestar’ orchard was used. Pre- and post-harvest (pre-senescent) photosynthetic light response curves were generated at leaf temperatures of 20–40 °C. Stomatal conductance showed increased sensitivity to increasing leaf temperature after harvest, resulting in a reduction in the optimum temperature for photosynthesis from 25–30 to 20–25 °C. This ensured the maintenance of high instantaneous leaf water use efficiency (WUE) post-harvest at all temperatures, compared to reductions in WUE but higher photosynthetic rates at high leaf temperature pre-harvest. We suggest that this reflects a change from a carbohydrate-demanding strategy (high sink demand) pre-harvest, to a water-conserving strategy post-harvest when sink demand is reduced. Following harvest, daily irrigation was either shut off or continued for 11 days, and light-saturated gas exchange measured regularly at varying levels of VPD in droughted trees. Photosynthetic rates, stomatal conductances and intercellular CO2 concentration (ci) remained relatively constant for the first 6 days, followed by reductions linked to a period of high ambient atmospheric evaporative demand and subsequent partial recovery. Droughted and non-droughted trees showed similar gas exchange values at the end of the droughting period when measured at 25 °C, but gas exchange of droughted trees remained repressed when measured at 30 °C due to increased non-stomatal limitation. Throughout the study, only cuvette VPD levels above 3.5 kPa (measured at 30 °C) significantly reduced gas exchange, with no interaction with duration of droughting. This study showed that post-harvest stomatal control was more attuned to ambient atmospheric evaporative demand in the orchard than to slowly developing soil moisture stress. We conclude that both atmospheric factors and changing sink demand influence stomatal control of apple leaves post-harvest, and that this should be taken into account when determining irrigation strategies. [Copyright &y& Elsevier]

A range of plant and environmental variables is known to influence the efficacy of herbicides. This paper explores whether environmental factors influencing efficacy of a herbicide can be quantified by analysing a set of industry data involving 59 experiments conducted throughout Australia in the years 1986–1995 for clodinafop-propargyl on Avena spp. A spline method was used to analyse the combined data set of observed and interpolated covariates. In addition to dose, it was found that efficacy was significantly influenced by maximum temperature on the day of application, spray water volume, the interaction of maximum temperature and spray volume, the sum of minimum temperatures experienced in the 7 days prior to application, and the soil moisture deficit estimated for day 10 prior to application. The findings are discussed in relation to testing of new products for providing commercial factor-adjustment information as an additional, marketable outcome of existing product testing procedures. Advantages of the spline model over the commonly used log–logistic model for evaluating dose–response and factor-adjustment relationships are presented. [ABSTRACT FROM AUTHOR]

Abscisic acid (ABA) concentration and plant and soil water potentials were determined in leaves of three cultivars of Coleus blumei Benth. cvs. Marty, Buckley Supreme and PI354190, chosen for their differences in sensitivity to drought, SO2 and/or chilling stress. Plants were subjected to ‘gradual’ soil moisture stress (SMS) for 0–6 days, during which time the soil dried out slowly and to more ‘rapid’ SMS for 0–9 days where the soil dried out at a faster rate. Plants were propagated from clonal stock in the greenhouse and transferred to the growth chamber, where they were maintained for 1 week prior to beginning water stress treatment. ABA concentration was determined as the methyl ester using a gas chromatography ‐ electron capture detector method. Samples for ABA determinations were taken from the third pair of leaves from the apex at the same time each day (1430 h). Measurements of stomatal conductance (C5) and leaf water potential (ψ1) were made on the fourth pair of leaves from the apex, using the same plants as those sampled for ABA. During the more rapid stress portion of the study soil matric potentials (ψm) were monitored on a daily basis. Despite large cultivar differences in ABA concentration at 0–6 days, by 7–9 days these differences had largely disappeared. Except for drought‐insensitive cv. Marty, there was generally little correlation between ABA levels and measurements of plant and soil water status at 7–9 days.