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An experiment has been conducted in the form of split plots in a randomized complete block design with three replications at the Agricultural and Natural Resources Research Institute in Zahak to evaluate the effect of drought stress and potassium application on yield and morphophysiological traits of safflower (Goldasht cultivar) under saline irrigation conditions (EC 6 dS.m-1) in 2018-2019. Drought stress irrigation regimes have been tested at three levels (irrigation after 45% (control), 65%, and 85% of admissible moisture depletion) as the main factor, and potassium fertilizer at four levels (0, 75, 150, and 225 kg.ha-1) as the sub factor. According to the findings, drought stress has reduced plant height, number of heads per plant, number of seeds per head, seed and biological yield, and relative water content. The use of potassium, on the other hand, has increased the above traits greatly. Irrigation after 45% moisture depletion increases seed yield by 42.32%, compared to irrigation after 85% moisture depletion. Interaction of drought stress and potassium has had a significant effect on number of branches per plant, 1000-seed weight, leaf chlorophyll index, soluble carbohydrate content, and seed oil percentage, with the highest amount observed after 45% water drainage and application of 225 kg K ha-1. [ABSTRACT FROM AUTHOR]

Purslane (Portulaca Oleracea L.) is a valuable medicinal plant growing in hot and dry conditions. Since drought stress is one of the most important factors limiting the production of agricultural products in these regions, this study aimed to evaluate the tolerance of different purslane landraces to drought stress in the greenhouse of Payame Noor University of Daregaz during the spring 2016. The experiment was as factorial based on completely randomized design with four levels of drought stress (field capacity, 75% FC, 50% FC and 25% FC), 5 landraces of purslane (Qom, Kalat, Sabzevar, Yazd, Gachsaran), and with three replications. The studied traits were relative water content, membrane sustainability index, photosynthetic pigment contents, chlorophyll sustainability index (the amount of chlorophylls and carotenoids), proline content, soluble carbohydrates, and fresh and dry weight of roots in two stages of vegetative and reproductive growth. Results showed that an increase in water stress level decreased the relative water content and cell membrane stability index while increasing the leaf chlorophyll index, carotenoid content, proline, and carbohydrates in different landraces of purslane. Results also indicated that the landraces of Gachsaran and Yazd had higher membrane stability index, lower RWC, and lower chlorophyll content under stress. Among the studied landraces, Qom and Kalat showed significant superiority compared to Sabzevar, Yazd and Gachsaran landraces in terms of proline and soluble carbohydrates. Also, the results showed that with increasing drought stress, fresh and dry weight of roots, leaves, and stems reduced at vegetative and generative stages of plant development such that the highest morphological and physiological traits in two stages of vegetative and reproductive growth were observed in 75% and 100% of field capacity and the minimum levels of these traits were obtained in 25% of field capacity. In general, Qom and Kalat landraces were more tolerant to drought stress compared to other landraces while Gachsaran, Yazd, and Sabzevar due to the relatively weak response to drought stress in most of the measured traits, were evaluated as susceptible landraces to drought stress.

Abstract Background and Objective: The goals of study were to recognize the effects of water deficit on eco-physiological and agronomic responses of safflower and introducing drought tolerant genotypes to cultivate in saline and dry lands. Materials and Methods: The experiment was conducted as split plot based on randomized complete blocks design with three replications in the East Azarbaijan Agriculture and Natural Resources Research and Education Center during two cropping seasons (2017-19). The experimental factors included drought stress as non-stressed and stressed from flowering to maturity and six safflower genotypes including Padideh, Golemehr, Mexico14, Mexico248, Mexico295 and Parnian. Results: Seed and oil yields and yield components of genotypes decreased by drought. Water deficit stress decreased RWC, stomatal conductance and leaf chlorophyll index significantly. Amounts of these characters were significantly different among genotypes. Correlations among studied traits were significant. Stomatal conductance and RWC indicated significant correlations with capitulum number per plant and oil percent. Also RWC indicated significant correlation with seed yield. Correlations among capitulum number per plant and grain number per capitulum with each other and seed oil percent, seed and oil yields, were positive and significant. These yield components had important role in productivity. Conclusion: stomatal conductance and RWC are able to reflect the effects of late season drought stress on safflower and can be used to select drought-tolerant genotypes. Golemehr, Mexico14, Mexico248 and Mexico295 genotypes indicated higher seed and oil yields in both normal and drought conditions and were seen suitable to cultivate in saline areas around Ormieh lake and areas with similar climate.

To investigate the effects of late season drought on yield components, seed and oil yields and some physiological indices related to drought tolerance in promise genotypes of safflower, an experiment was conducted as split plot based on a randomized complete blocks design with three replications in saline areas of the East Azarbaijan Agriculture and Natural Resources Research and Education Center during the cropping season of 2018-19. The experimental factors included drought stress (non-stressed and stressed from flowering to maturity) and six safflower genotypes (Padideh, Gazagi, 59, 68, 97 and 132 lines). Drought stress decreased yield components, seed and oil yields, leaf chlorophyll index, stomatal conductance and RWC and increased leaf temperature significantly. Amounts of these traits were significantly different among genotypes. Correlations among these indices and with seed and oil yields were significant. Also all yield components had important role in productivity. In all water conditions, Padideh variety and promise line 68 had higher amounts of physiological indices and indicated higher seed and oil yields. Therefore, Leaf chlorophyll index, stomatal conductance, RWC and leaf temperature are able to reflect the effects of water deficit on safflower genotypes and could be used in the drought tolerant genotypes selection. [ABSTRACT FROM AUTHOR]

Remote sensing techniques have been considered a new technology in worldwide agriculture for diagnosing the plant nutritional demand. Fertilizer management efficiency is a goal to be achieved, and modern tools based on remote sensing are promising for monitoring the crop needs. This study aimed to evaluate the agronomic performance and relative economic return of white oat under nitrogen rates, as well as to verify whether the normalized difference vegetation index (NDVI) and leaf chlorophyll index (LCI) could be used for topdressing nitrogen fertilization management, in white oat. Treatments consisted of five topdressing nitrogen fertilization strategies: T1 - 160 kg ha-1 (reference rate); T2 - 90 kg ha-1 (recommended rate); T3 - 60 kg ha-1 (economic rate); T4 - 30 kg ha-1 (when NDVI < 90 % of T1); and T5 - 30 kg ha-1(when LCI < 90 % of T1). The white oat did not respond to the topdressing nitrogen fertilization. Its temporal monitoring using spectral indices allowed dispensing the topdressing nitrogen fertilization without reducing the grain and biomass yields and the leaf nitrogen content, when compared to the recommended management (90 kg ha-1 of N as topdressing), with no differences between the evaluated spectral indices. Thus, both the NDVI and LCI spectral indices are promising tools for the topdressing nitrogen fertilization management in the white oat crop.

• Salinity treatments induced negative effects on photosynthesis, stomatal conductance, leaf chlorophyll index, plant growth and dry matter accumulation for both cultivars. • 'Chemlali' has a higher resistance to increasing NaCl salinity. • Mannitol accumulation increased under salinity stress for 'Chemlali' and seems to play a major role in stress tolerance. • GA3 application alleviated the negative effects of salt stress on the ecophysiological parameters especially for 'Koroneiki'. Soil salinization is considered as one of the most important risks for agricultural soils. The objective of this experiment was to study the ecophysiological and the biochemical behaviour of two cultivars of Olea europaea L., 'Chemlali' and 'Koroneiki' under two salinity levels (100 and 200 mM NaCl) and the potential alleviation induced by gibberellic acid (GA3) foliar sprays. Salinity treatments significantly decreased photosynthetic assimilation rate and stomatal conductance compared to the control for both cultivars, but 'Chemlali' showed a higher resistance to increasing NaCl salinity compared to 'Koroneiki'. Leaf chlorophyll index also reduced gradually with increasing salinity concentration compared to the control. At the end of the experiment, a decrease in growth and dry matter accumulation was observed. Under high salinity stress, a significant decrease in root DW was recorded by 37% and 59% for 'Chemlali' and 'Koroneiki', respectively. High salinity stress decreased also shoot DW up to 51% for 'Chemlali'. However, mannitol concentration increased under increasing salinity levels compared to control for 'Chemlali' cultivars. Interestingly, foliar application of GA3 alleviated the negative effects of salinity on ecophysiological parameters especially for 'Koroneiki'. Indeed, GA3 improved photosynthetic assimilation up to 14% for 'Chemlali' and 36% for 'Koroneiki' compared to high salinity treatment. Both cultivars showed an increase in leaf chlorophyll index after applying GA3. Under high salinity combined with GA3, growth and dry weight were increased compared to salt stressed plants without GA3. The obtained results report that 'Chemlali' cultivar is more tolerant to salinity than 'Koroneiki' and suggest that GA3 plays an important role to reduce negative effects of NaCl salinity. [ABSTRACT FROM AUTHOR]

In order to investigate the effect of different levels of plant density and irrigation on some morphologic and physiologic responses and antioxidants activities in chickpea cv. Hashem, an experiment was conducted at Goonbad-e-Kavoos region during 2012-2013 cropping season. Treatments were arranged as split plot in randomized complete block design with four replications. Different irrigation regime levels (rainfed without irrigation, irrigation at flowering stage, and irrigation during pod filling stage) were assigned to main plots and sub-plots comprised of different plant densities (20, 30, 50, and 70 plants/m2). Results showed that different irrigation regimes significantly affected traits except for days to 50% flowering and plant height but plant density factor had significant impacts only on days to 50% flowering, plant height, days to physiologic maturity, seed yield, biologic yield, and leaf chlorophyll index. Results showed that irrigation caused significant increase in leaf relative water content and leaf chlorophyll index while it decreased grain protein content, superoxide dismutase and catalase activities. Maximum and minimum grain protein contents were produced in no-irrigation and irrigation during pod filling stage, respectively. Meanwhile, the maximum and minimum grain yield was gained by irrigation at flowering stage and rainfed without irrigation, respectively. Under plant density levels, the maximum and minimum grain yield was produced in 70 plants/m2 and 20 plants/m2, respectively. Irrigation at flowering stage × 70 plants/m2 had the highest grain yield among all treatments of the study.

The objective of this paper is to investigate the sensitivity of reflectance to the variation in biochemical and biophysical variables at leaf, canopy, and regional scales using a modeling approach. The results show that, at the leaf scale, the variations in chlorophyll a+b content, the leaf structure parameter, and the water content dominate the reflectance variance in the visible light (VIS), near infrared (NIR), and short-wave infrared (SWIR) regions, respectively. At the canopy scale, the sensitivity of reflectance to variation in the leaf structure parameter is very slight. For sparse foliage cover (leaf area index ), LAI is the most important variable to the canopy reflectance. As LAI increases, the sensitivity of reflectance to variation in LAI is reduced to a very low value. Moreover, chlorophyll a+b, dry matter, and water content control the variation of canopy reflectance in the VIS, NIR, and SWIR regions, respectively. At the regional scale, the sensitivity of reflectance to variation in vegetation variables is highly influenced by the mixed pixels. Thirty-six vegetation indices (VIs) are chosen in this paper to illustrate the scale dependence of the estimation accuracy of vegetation variables. The results show that the relationships between the VIs and the variables highly depend on the observation scale. For chlorophyll a+b content estimation, transformed chlorophyll absorption in reflectance index (TCARI), Blue Green pigment Index, leaf chlorophyll index (LCI), modified Normalized Difference (mND705), and Plant Biochemical Index at the leaf scale and canopy scale of and TCARI at the canopy scale of are highly related. The correlation between the indices and chlorophyll content in the regional scale is, however, much lower. For water content estimation, disease water stress index (DSWI), leaf water vegetation index 2 (LWVI_2), moisture stress index (MSI), normalized difference infrared index (NDII), normalized difference water index (NDWI), hyperspectral perpendicular vegetation index (RVI), SWIR water stress index (SIWSI), SR water index (SRWI), and water index (WI) are good choices at the leaf scale and canopy scale of , while at the canopy scale of and the regional scale, the correlation between the indices and water content is very low. For LAI estimation, VIs, including the Greenness Index, simple ratio (SR), Normalized Difference VI, modified soil-adjusted vegetation index (MSAVI), modified triangular vegetation index 1 (MTVI1), modified triangular vegetation index 2 (MTVI2), optimized soil-adjusted vegetation index (OSAVI), modified chlorophyll absorption ratio index 1 (MCARI1), modified chlorophyll absorption ratio index 2 (MCARI2), Enhanced VI, LAI Determining Index, renormalized difference vegetation index (RDVI), Spectral Polygon VI, Wide Dynamic Range VI, and triangular vegetation index (TVI), have high correlation with LAI at the canopy scale of while a low correlation at the canopy scale of and the regional scale. [ABSTRACT FROM PUBLISHER]

Many commercial pecan [Carya illinoinensis (Wangenh.) K. Koch] producers routinely spray foliar urea and sulfur (S) in combination with their fungicide sprays, despite very little information available in the scientific literature regarding the effects of these practices on pecan production. The objectives of this study were to investigate the effects of foliar application of elemental S and urea, alone and in combination, on pecan leaf tissue nitrogen (N) and S concentration, pecan nut quality, leaf chlorophyll index (LCI), and pecan scab control. Foliar S sprays increased pecan nut weight over the control in 2 of 3 years of study. Pecan nut weight was unaffected by foliar urea sprays compared with the control, but nut weight was lower for foliar urea sprays compared with foliar S sprays in the first 2 years of study. Neither foliar S nor urea sprays affected pecan scab incidence or severity. Foliar S sprays failed to increase leaf S concentration throughout the study. Pecan leaf N and leaf S concentrations were lower in the foliar urea treatment than in the control and foliar S treatments during the initial year of study; however, no treatment differences were observed for urea after Year 1. Foliar S application enhanced LCI in 2011 and 2012. Leaf chlorophyll index was also increased by the combination of foliar urea and S in 2012. These results suggest that foliar S sprays may provide pecan producers with a tool with which to maximize nut size and increase the profitability of their crop. [ABSTRACT FROM AUTHOR]

Lychee (Litchi chinensis Sonn. cv. 'Mauritius') trees growing in calcareous soils are prone to iron (Fe) deficiency, typically prevented by soil application of chelated Fe, which is very expensive compared to iron sulfate (FeSO4). Therefore, the effects of foliar applications of weak acids (ascorbic or dilute sulfuric acid), weak acids plus FeSO4, or a soil drench of chelated iron (Fe-EDDHA) on leaf chlorophyll index, leaf ferrous iron (Fe2+) and total Fe concentrations, leaf gas exchange and plant dry weight were determined for 2-year-old lychee trees growing in calcareous soil in containers. Treatments were: foliar applications of ascorbic acid in deionized (DI) water plus surfactant, sulfuric acid in DI water plus surfactant, ascorbic acid in DI water plus FeSO4 plus surfactant, sulfuric acid in DI water plus FeSO4 plus surfactant, FeSO4 in DI water plus surfactant, FeSO4 in DI water with no surfactant, FeSO4 in well water plus surfactant, sulfuric acid plus FeSO4 in well water plus surfactant, surfactant in DI water. An additional treatment was chelated iron (Fe-EDDHA) applied to the soil. The organosilicone compound Freeway® was used as the surfactant. Well water was used instead of DI water in two treatments because fertilizers are often mixed with water from a well that typically has a pH much higher than that of DI water. Foliar treatments were applied at 4-week intervals for 24 weeks and chelated iron was applied to the soil at the time of first foliar treatments and 8 and 16 weeks later. There was generally no difference in leaf chlorophyll index among plants receiving chelated iron as a soil drench or foliar treatments containing FeSO4 plus surfactant with or without organic acid. Foliar applications of acid with no FeSO4 resulted in a lower leaf chlorophyll index than soil-applied Fe-EDDHA or any of the foliar treatments containing FeSO4 plus surfactant. Leaf total Fe and Fe2+ concentrations were generally highest for plants in the soil-applied Fe-EDDHA treatment and all foliar application treatments containing FeSO4 plus surfactant. Net CO2 assimilation (Anet), stomatal conductance (gs), transpiration (Tr) and leaf, stem, root and total plant dry weights were highest for plants treated with soil-applied Fe-EDDHA or foliarly applied FeSO4 with no surfactant. Further studies indicated that the surfactant Freeway® inhibits leaf gas exchange and plant growth. The results indicate that foliar applications of FeSO4 are almost as effective as soil applications of chelated Fe for eliminating or preventing Fe deficiency symptoms of lychee trees growing in calcareous soil. While the addition of a surfactant to the foliar spray mixture appears to be necessary for preventing Fe deficiency, care must be taken when selecting a surfactant for foliar applications of FeSO4 to be sure that there are no negative effects on leaf gas exchange and plant growth. [ABSTRACT FROM AUTHOR]