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In this study, the effects of repeated cycles of drying and rehydration on some physiological traits were assessed in long shelf-life tomatoes cultivated in a typical semi-arid area of Southern Italy. Three Sicilian landraces (‘Custonaci’, ‘Salina’, and ‘Vulcano’) from the germplasm collection at CNR-IBE (Catania, Italy) and a commercial tomato mini-plum (‘Faino Hy., control) were investigated under three water regimes: DRY (no irrigation), IRR (long-season full irrigation) and REW (post-drought rewaterings). Net photosynthetic assimilation rate (Pn), leaf transpiration (E), stomatal conductance (gs), instantaneous water use efficiency (WUEi), leaf intercellular CO2 (Ci, ppm), and leaf temperature (°C), were measured during the growing season. At harvest (late July), fruit production per plant was measured and ripened fruits were analysed for total solids (TS), soluble solids (SS), reducing sugars (RS), vitamin C (AscA), and total phenols (TP). Pn promptly responded to rewatering (REW), quickly increasing immediately after irrigation, and declined with soil drying up. All genotypes had similar physiological pathways in DRY, but in IRR, ‘Faino’ had higher Pn (up to 31 μmol CO2 m−2s−1) and E (up to 18 mmol H2O m−2s−1). Stomatal conductance (gs) after rewatering steeply increased and quickly declined after that. All local landraces had the same gs in IRR and REW. Variations in RWC were less pronounced than those in other physiological parameters. WUEi in REW and DRY proceeded similarly (up to 3 μmol CO2 mmol H2O). Irrigation in REW significantly promoted plant productivity over the DRY control (up to +150% in ‘Vulcano’). TS and SS in REW were lower than those in DRY, but higher (+19 and +7%, respectively) than in IRR. Vitamin C was greater in DRY and REW (26 and 18% higher than in IRR, respectively). TP in all local tomatoes were significantly higher (up to +29% in ‘Vulcano’) than those in the commercial control. Water regime had a minor effect on TP in ‘Custonaci’ and ‘Salina’. Principal Component Analysis (PCA) provided information on the changes in physiological and fruit quality traits in tomatoes in relation to cultivars and water regimes. The results of this study also revealed that a water-saving irrigation strategy where few irrigations are applied after prolonged periods of drought might be profitable in terms of fruit production enhancement in long shelf-life tomatoes and that limited rewaterings in most cases, help retaining high levels of fruit quality traits.

Wheat landraces are traditional varieties that have evolved over generations in response to local environments and farming practices and therefore exhibit remarkable adaptability to challenging climatic conditions and low-input farming systems. While the suitability of Mediterranean landraces to non-optimal climatic conditions during anthesis and grain ripening stage have been previously assessed, the role of photosynthesis efficiency and stomatal control on this resilience remains unexplored. This study aims to evaluate the relationship between grain yield and the post-anthesis flag leaf gas exchanges of Sicilian wheat landraces under irrigated and rainfed conditions and to compare these traits to modern durum (Triticum turgidum subsp. durum) and bread wheat (T. aestivum) varieties. Results indicate that wheat landraces respond to water availability similarly to modern varieties, reducing stomatal conductance by 26.8% and net photosynthesis by 18.1% under rainfed conditions, resulting in 10.6% lower grain yield compared to irrigated conditions. However, some landraces demonstrate comparable or even higher flag leaf net photosynthesis rates and lower transpiration levels, leading to higher yields in both rainfed and irrigated conditions, confirming their value as a source of gene pool for wheat breeding programs in drought-prone Mediterranean regions.

Increases in water use efficiency (WUE) and the reduction of negative impacts of high temperatures associated with high solar radiation are being achieved with the application of fine particle film of calcined and purified kaolin (KF) on the leaves and fruits of various plant species. KF was applied on young Coffea arabica and Coffea canephora plants before their transition from nursery to full sunlight during autumn and summer. The effects of KF were evaluated through the responses of leaf temperature (Tleaf), net CO2 assimilation rate (A), stomatal conductance (gs), transpiration (E), WUE, crop water stress index (CWSI), index of relative stomatal conductance (Ig), initial fluorescence (F0), and photosynthetic index (PI) in the first 2–3 weeks after the plant transitions to the full sun. All measurements were performed at midday. In Coffea plants, KF decreased the Tleaf up to 6.7°C/5.6°C and reduced the CWSI. The plants that were not protected with KF showed lower A, gs, E, and Ig than those protected with KF. C. canephora plants protected with KF achieved higher WUE compared with those not protected by 11.23% in autumn and 95.58% in summer. In both Coffea sp., KF application reduced F0, indicating reduced physical dissociation of the PSII reaction centers from the light-harvesting system, which was supported with increased PI. The use of KF can be recommended as a management strategy in the transition of Coffea seedlings from the nursery shade to the full sunlight, to protect leaves against the excessive solar radiation and high temperatures, especially in C. canephora during the summer.

Verticillium wilt of olive (VWO), caused by the soil borne fungus Verticillium dahliae, is one of the most relevant diseases affecting this crop worldwide. One of the best VWO management strategies is the use of tolerant cultivars. Scarce information is available about physiological and structural responses in the leaves of olive cultivars displaying different levels of tolerance to VWO. To identify links between this phenotype and variations in functional characteristics of the leaves, this study examined the structural and physiological traits and the correlations among them in different olive varieties. This evaluation was conducted in the presence/absence of V. dahliae. On the one hand, no leaf trait but the area was related to VWO tolerance in the absence of the pathogen. On the other hand, after inoculation, susceptible cultivars showed lower leaf area and higher leaf mass per area and dry matter content. Furthermore, at the physiological level, these plants showed severe symptoms resembling water stress. Analyzing the relationships among physiological and structural traits revealed differences between tolerant and susceptible cultivars both in the absence and in the presence of V. dahliae. These results showed that olive leaves of VWO-tolerant and VWO-susceptible cultivars adopt different strategies to cope with the pathogen.

Wood ash as a soil amendment has gained wide spread acceptance in the recent years as a sustainable alternative to chemical fertilizers, although information regarding the effects of its application on maize growth and yield in the context of climate change and increasing drought severity is lacking till date. In the present study, field and pot trials were carried out at the experimental farm of the University of Padova at Legnaro (NE Italy) in a silty-loam soil in order to investigate the effects of soil amendment with wood ash (0.1% w/w, incorporated into the 0.2-m top soil) on the bioavailability of mineral elements and their uptake by maize. Characteristics analyzed included plant growth, leaf transpiration dynamics, and productivity in two contrasting hybrids, P1921 (drought sensitive) and D24 (drought tolerant). Wood ash contained relevant amounts of Ca, K, Mg, P, and S, and hazardous levels of Zn (732 mg kg−1), Pb (527 mg kg−1), and Cu (129 mg kg−1), although no significant changes in total soil element concentration, pH, and electrical conductivity were detected in open field. Ash application led to a general increasing trend of diethylene triamine penta-acetic acid (DTPA)-extractable of various elements, bringing to higher grain P in D24 hybrid, and Zn and Ni reductions in P1921 hybrid. Here, the results demonstrated that ash amendment enhanced shoot growth and the number of leaves, causing a reduction of harvest index, without affecting grain yield in both hybrids. The most relevant result was a retarded inhibition of leaf transpiration under artificial progressive water stress, particularly in the drought-tolerant D24 hybrid that could be sustained by root growth improvements in the field across the whole 0–1.5 m soil profile in D24, and in the amended top soil in P1921. It is concluded that woody ash can be profitably exploited in maize fertilization for enhancing shoot and root growth and drought tolerance, thanks to morphological and physiological improvements, although major benefits are expected to be achieved in drought tolerant hybrids. Attention should be payed when using ash derived by metal contaminated wood stocks to avoid any health risk in food uses.

Quantifying heat and mass exchanges processes of plant leaves is crucial for detailed understanding of dynamic plant-environment interactions. The two main components of these processes, convective heat transfer, and transpiration, are inevitably coupled as both processes are restricted by the leaf boundary layer. To measure leaf heat capacity and leaf heat transfer coefficient, we thoroughly tested and applied an active thermography method that uses a transient heat pulse to compute τ, the time constant of leaf cooling after release of the pulse. We validated our approach in the laboratory on intact leaves of spring barley (Hordeum vulgare) and common bean (Phaseolus vulgaris), and measured τ-changes at different boundary layer conditions.By modeling the leaf heat transfer coefficient with dimensionless numbers, we could demonstrate that τ improves our ability to close the energy budget of plant leaves and that modeling of transpiration requires considerations of convection. Applying our approach to thermal images we obtained spatio-temporal maps of τ, providing observations of local differences in thermal responsiveness of leaf surfaces. We propose that active thermography is an informative methodology to measure leaf heat transfer and derive spatial maps of thermal responsiveness of leaves contributing to improve models of leaf heat transfer processes.

A clear understanding of plant transpiration is a crucial step for water cycle and climate modeling, especially for arid ecosystems in which water is one of the major constraints. Traditional field measurements of leaf scale transpiration are always time-consuming and often unfeasible in the context of large spatial and temporal scales. This study focused on a dominant native plant in the arid land of central Asia, Haloxylon ammondendron, with the aim of deriving the leaf-scale transpiration through hyperspectral reflectance using Partial Least Squares Regression (PLSR) analysis. The results revealed that the PLSR model based on the first-order derivative spectra at wavelengths selected through stepwise regression analysis can closely trace leaf transpiration with a high accuracy (R2 = 0.78, RMSE = 1.62 µmol g-1 s-1). The accuracy is also relatively stable even at a spectral resolution of 10 nm, which is very close to the bandwidths of several running satellite-borne hyperspectral sensors such as Hyperion. The results also proved that the first-order derivative spectra within the shortwave infrared (SWIR) domain, especially at 2435, 2440, 2445, and 2470 nm, were critical for PLSR models to predict leaf transpiration. These findings highlight a promising strategy for developing remote sensing methods to potentially characterize transpiration at broad scales.

Deficit irrigation is a valid alternative to conventional irrigation to save water while maintaining high productivity in tomatoes. However, crop sensitivity to water stress due to deficit irrigation may change with the growth stage. To assess the physiological and agronomic responses of processing tomatoes to deficit irrigation applied at critical stages, a field experiment was conducted in a coastal site of Southern Italy, where seven irrigation treatments differing for daily evapotranspiration (ETc) restored (100%—full or 50%—deficit) and the time of watering (long-season or limited to the vegetative period or to flowering) were applied to processing tomatoes cv. Hypeel F1. Plants continuously irrigated and those irrigated only at flowering maintained higher rates of leaf transpiration (E) and stomatal conductance (gs) over those irrigated only during the vegetative period. Fruit yield was the greatest under long-season full irrigation (51 t ha−1). Severe soil water deficit during flowering, more than during the vegetative period, adversely affected crop productivity. Irrigation water use efficiency (IWUE) was maximized under long-season deficit irrigation (>19 kg m−3) or deficit irrigation during flowering (>16 kg m−3). E and gs measured at early or mid-flowering may be adopted as valuable indicators to predict crop productivity; however, they may be altered under high vapor pressure deficit (VPD). Predawn water potential, being little affected by VPD, is a more reliable parameter than leaf transpiration and stomatal conductance under these climatic conditions.

Euphorbia pulcherrima Wild.'Lilo' was grown in containers in 60% peat, 30% perlite and 10% clay (v/v) mixture, with different irrigation treatments based on soil water potential. Plants were watered at two levels of drought stress: -50kPa or wilting. The treatments were applied at different stages of plant development for a month or soil was brought to the moisture stress only twice. Additionally, some plants were watered at -50 kPa during the entire cultivation period while the control plants were watered at -5kPa. Plants were also kept at maximum possible moisture level (watering at -0,5kPa) or close to it (-1.OkPa) through the entire growing period. Soil water potential was measured with tensiometer. Drought stress applied during entire cultivation period or during the flushing stage caused significant reduction in transpiration and conductance of leaves. Stress applied during bract coloration stage had not as great effect on the stomatal conductance and transpiration of leaves as the similar stress applied during the flushing stage. High soil moisture increased stomatal conductance and transpiration rate, respectively by 130% and 52% (flushing stage), and 72% and 150% (bract coloration stage) at maximum, compared to the control.

This research aimed to evaluate the gas exchange and growth index of Brachiaria decumbens under five water supply (3.84, 4.39, 6.19, 8.62 and 10.46 mm day-1). A completely randomized with split-plot design with five irrigation depth being the parcels and ages (10, 17, 24 and 31 days), the subparcels, with four replicates. It was observed interaction between irrigation depth and ages for leaf transpiration, leaf temperature, rate of photosynthesis and leaf weight ratio. Quadratic responses with minimum values were observed to the internal CO2 concentration and specific leaf area (0.0055 m² leaf g-1 leaf) with advance in ages. The internal concentration of CO2 revealed values of 220.09 and 176.20 ppm to 10 and 31 days, respectively, withminimum (173.68 ppm) to 27 days. It was observed quadratic response with maximum value (25.04 g m-2 leaf day-1) to the net assimilation rate with increasing ages. Decreasing linear responses were observed to the relative growth rate and leaf area ratio with increasing ages. The relative growth rate presented values of 0.097 and 0.048 g g-1 day-1, with 10 and 31 days, respectively. The growth ages provided changes on gas exchange and growth index of Brachiaria grass, however, these characteristics are little influenced by irrigation depth under the conditions of this study.ResumoObjetivou-se com esse estudo avaliar trocas gasosas e índices de crescimento no capim-braquiária manejado sob cinco lâminas de irrigação (3,84; 4,39; 6,19; 8,62 e 10,46 mm dia-1) e quatro idades, num delineamento inteiramente casualizado em arranjo de parcelas subdivididas, sendo as lâminas de irrigação estudadas nas parcelas e as idades (10, 17, 24 e 31 dias) nas subparcelas, com quatro repetições. Constatou-se interação entre lâminas de irrigação e idades nas variáveis: transpiração foliar, temperatura da folha, taxa de fotossíntese e razão de peso foliar. Verificou-se resposta quadrática com ponto de mínimo para a concentração interna de CO2 e área foliar específica (0,0055 m² de folha g-1 de folha) em função do avanço nas idades. A concentração interna de CO2 apresentou valores estimados em 220,09 e 176,20 ppm aos 10 e 31 dias de crescimento, respectivamente, com valor mínimo (173,68 ppm) aos 27 dias. Verificou-se resposta quadrática com ponto de máximo (25,04 g m-2 de folha dia-1) para a taxa de assimilação líquida com o aumento nas idades. Observou-se resposta linear decrescente para taxa de crescimento relativo e razão de área foliar com aumento nas idades. A taxa de crescimento relativo revelou valores de 0,097 e 0,048 g g-1 dia-1, com 10 e 31 dias de crescimento, respectivamente. As idades de crescimento proporcionam mudanças nas trocas gasosas e nos índices de crescimento do capim-braquiária, porém, tais variáveis são pouco influenciadas pelaslâminas de irrigação nas condições do presente estudo.

Estudos sobre os fatores envolvidos na adaptação das plantas micropropagadas ao ambiente ex vitro são imprescindíveis para definir quais os procedimentos devem ser utilizados durante a fase de aclimatização. O objetivo deste trabalho foi avaliar a contribuição da densidade estomática e da presença de cera epicuticular no controle da perda de água, em folhas de bananeiras micropropagadas. Para tanto, brotações axilares oriundas da etapa de multiplicação in vitro foram enraizadas por 24 dias, em meio MS, contendo 1mg L-1 de ácido naftalenoacético (ANA) e 6g L-1 de ágar e, posteriormente, foram aclimatizadas por 120 dias. Os tratamentos consistiram de folhas formadas in vitro e em diferentes estádios de aclimatização, tais como: T1 - folhas de plantas ao final da fase de enraizamento in vitro; T2 - folhas persistentes de plantas aos 30 dias de aclimatização; T3 - novas folhas de plantas aos 30 dias de aclimatização (folhas de transição); T4 - folhas de transição de plantas aclimatizadas por 60 dias; T5 e T6 - novas folhas de plantas aclimatizadas por 60 dias e 120 dias, respectivamente. Foram avaliados os seguintes parâmetros: a densidade estomática, o conteúdo relativo de água e a presença de cera epicuticular. Foi verificado que folhas de plantas provenientes da fase de enraizamento in vitro, em ambiente mixotrófico, apresentam reduzido controle sobre a perda de água e alta densidade estomática. A reduzida transpiração das folhas formadas na fase de aclimatização pode ser atribuída ao menor número de estômatos por unidade de área foliar, à maior capacidade destes em restringir a perda de água e à presença de cera epicuticular.Studies concerning factors involved in the adaptation of micropropagated plants to ex vitro conditions are indispensable to define which procedures should be used during the acclimatization phase. The objective of this research was to evaluate the presence of stomata and epicuticular wax on water loss control in micropropagated banana plants. For 24 days axillary buds were rooted in MS medium supplemented with NAA (1mg L-1) and agar (6g L-1), and afterwards the plantlets were acclimatized for 120 days. The treatments consisted of the evaluation of in vitro leaves and at different acclimatization stages, as follows: T1 - leaves of plants at the end of the in vitro rooting phase T2 - persistent leaves of plants after 30 days of acclimatization; T3 - new leaves from plants after 30 days of acclimatization (transition leaves); T4 - transition leaves from plants after 60 days of acclimatization; T5 and T6 - new leaves from plants after 60 and 120 days of acclimatization, respectively. Data regarding stomatal density, relative water content and presence of epicuticular wax were also evaluated. It was verified that new leaves from plants rooted in vitro under mixotrophic condition presented hight stomatal density and hence a reduced control of water loss. The reduced transpiration of leaves formed during the acclimatization phase can be attributed to the small number of stomata per unit of leaf area associated to the largest capacity of these in restricting water loss, and the presence of epicuticular wax.