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Phenotypic plasticity is the ability of an organism to undergo reversible behavioral, morphological or physiological changes in response to environmental conditions. Phenotypic plasticity enables plants to cope with uncertain environmental conditions, such as drought. A primary plastic trait is the rate of stomatal response to changes in ambient conditions, which determines the amount of water lost via transpiration, as well as levels of CO2 absorption, growth and productivity. Here, we examined the differences between domesticated and wild tomato species and their responses to drought stress. We found that the domesticated tomato had a higher transpiration rate and higher stomatal conductance (gs). The domesticated tomato also had greater biomass and greater leaf area under drought conditions, as compared to the wild tomato. Despite the domesticated tomato's higher transpiration rate and higher gs, there was no difference between the photosynthetic rates of the two lines. Moreover, the wild tomato had a higher maximum rate of rubisco activity, which might explain its greater molecular and whole canopy water-use efficiency. The domesticated tomato's higher transpiration rate and greater leaf area led to its earlier exposure to drought stress, as compared to the wild tomato, which maintained higher levels of soil water, enabling it to maintain steady rates of whole-canopy stomatal conductance (gsc) for extended periods. The wild tomato was also more sensitive to the soil water availability and lowered its maximum transpiration rate at a higher soil-water-content level. Our results suggest that the domestication process of tomatoes favored morphological/anatomical performance traits over physiological efficiency.

Purpose Accessing freshwater resources becomes more complex in arid and semi-arid areas due to increased demands and declining water quality. Alternative water sources for agriculture such as saline and recycled water are currently being used. A better understanding of roots' response to irrigation with saline water is crucial for future agriculture in arid and semi-arid areas. Methods Three grapevine (Vitis) rootstocks were examined, and their roots' responses to salinity were studied. The rootstocks were planted in pots filled with sand and were grown in a commercial net house subjected to two salinity treatments: 10 mM and 30 mM NaCl (EC = 2 and 4 ds m-1, respectively). We measured root morphologic and anatomic properties at the end of the experiment. Results The specific root area increased in response to salinity due to reduced root tissue density. In addition, a reduction in the average root diameter also affected the specific root area by increasing the surface area to volume ratio. Plant biomass was allocated primarily to the shoot in all three rootstocks, reducing the root to shoot ratio. At the same time, the bottom part of the root zone was more affected by salinity. SO4 showed improved chloride and sodium exclusion, concomitant with a significant increase in its narrow roots' contribution to the surface area. Conclusion Narrow roots play a more prominent role in the acquisition of water and nutrients as salinity increases. Furthermore, a decrease in root tissue density and average diameter may contribute to salt exclusion from the roots.

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