The balance of survival: Comparative drought response in wild and domesticated tomatoes.

Plants have the ability to undergo reversible behavioral, morphological, or physiological changes in response to environmental conditions. This 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 (S. lycopersicum cv. M82) and wild tomato (S. pennellii) species and their responses to drought stress. The plants were grown in pots in a functional phenotyping platform (FPP) in a semi-controlled environment greenhouse. We found that the domesticated tomato had a higher transpiration rate (E) 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 E and higher gs, there was no difference between the photosynthetic rates (An) of the two lines. Moreover, the wild tomato had a higher maximum rate of rubisco activity (Vcmax), which might explain its greater leaf level and whole canopy water-use efficiency. The domesticated tomato's higher E 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 soil water availability and lowered its maximum transpiration rate (Emax) at a higher soil-water-content (SWC) level compared to the domesticated species. Our results suggest that the domestication of tomatoes favored morphological/anatomical performance traits over physiological efficiency.

Root system response to salt stress in grapevines (Vitis spp.): A link between root structure and salt exclusion.

Accessing freshwater resources for agriculture becomes more complex due to increasing demands and declining water quality. Alternative water sources, such as saline water, require ad hoc solutions. Therefore, understanding roots' response to saline water is crucial for future agriculture. We examined the response of three grapevine rootstocks (Paulsen 1103, Richter 110 and SO4) to salt stress. The rootstocks were subjected to two salinity treatments: 10 mM and 30 mM NaCl (EC = 2 and 4 ds/m, respectively). Root and shoot samples were taken at the end of the experiment for morphologic and ionomic analyses. The specific root area (SRA) increased in response to salinity for all three rootstocks due to root tissue density and average root diameter reductions. Salinity also led to increased root Na+ and Cl- contents and reduced root K+/Na+ ratio, parallel to increased leaf Cl- but not Na+ contents. SO4 showed improved chloride and sodium exclusion, concomitant with its highest SRA, resulting from the increase in its thin roots' contribution to the total root system surface area. We suggest that enhanced SRA combined with decreased root tissue density and diameter may improve grapevines' salt exclusion by less salt uptake from the soil.

Quantitative and comparative analysis of whole-plant performance for functional physiological traits phenotyping: New tools to support pre-breeding and plant stress physiology studies.

Plants are autotrophic organisms in which there are linear relationships between the rate at which organic biomass is accumulated and many ambient parameters such as water, nutrients, CO2 and solar radiation. These linear relationships are the result of good feedback regulation between a plants sensing of the environment and the optimization of its performance response. In this review, we suggest that continuous monitoring of the plant physiological profile in response to changing ambient conditions could be a useful new phenotyping tool, allowing the characterization and comparison of different levels of functional phenotypes and productivity. This functional physiological phenotyping (FPP) approach can be integrated into breeding programs, which are facing difficulties in selecting plants that perform well under abiotic stress. Moreover, high-throughput FPP will increase the efficiency of the selection of traits that are closely related to environmental interactions (such as plant water status, water-use efficiency, stomatal conductance, etc.) thanks to its high resolution and dynamic measurements. One of the important advantages of FPP is, its simplicity and effectiveness and compatibility with experimental methods that use load-cell lysimeters and ambient sensors. In the future, this platform could help with phenotyping of complex physiological traits, beneficial for yield gain to enhance functional breeding approaches and guide in crop modeling.