Stable Carbon Isotope Composition (δ¹³C), Water Use Efficiency, and Biomass Productivity of Lycopersicon esculentum, Lycopersicon pennellii, and the F₁ Hybrid

Abstract

Three tomatoes, Lycopersicon esculentum Mill. cv UC82B, a droughttolerant wild related species, Lycopersicon pennellii (Cor.) D'Arcy, and their F, hybrid, were grown in containers maintained at three levels of soil moisture. Season-long water use was obtained by summing over the season daily weight losses of each container corrected for soil evaporation. Plant biomass was determined by harvesting and weighing entire dried plants. Season-long Indirect means to evaluate WUJE,, accurately in field-grown plants are needed to improve our understanding of water relations and adaptation in native plants and to serve as selection criteria in crop improvement programs. Light-weight portable equipment for measuring rates of photosynthesis and transpiration ofindividual leaves or canopies are becoming commonplace. Such a measurement (4, 8, 13, 31) yields the WUEF of the plant part under measurement, and it represents the performance of that plant part at a specific time only. The relationship between such a point measurement and long-term plant performance is uncertain. Micrometeorological approaches to determine the water use efficiency (1) proportionally less than the rate of transpiration (2,3,6,7,20), except perhaps under very rare field conditions of extremely stagnant air (large boundary layer resistance) (1,3,6,7,31). Reduced stomatal aperture also simultaneously decreases the concentration of CO2 in the intercellular air spaces, Co. The isotopic discrimination at any moment in time against '3C02 as a substrate is inherent with the primary carboxylating enzyme of C3 photosynthesis, Rubisco. It is great when Ci is high, and the discrimination is reduced with decreasing Ci (2,16,21,22,29).Thus, 613C of a plant or plant part will reflect the integral of Ci over the time of tissue formation as well as the water use efficiency averaged over the growth period, WUEg.The enzymic discrimination against 13C is the major cause for the difference in plant 613C and a 13C of CO2 in the air, although minor isotopic fractionation occurs due to different diffusivities and solubilities of 13C02 and '2CO2 (14,16,21). Note also that the relationship between 6'3C and WUE, would be similar also if these two parameters were affected by photosynthetic perturbations of the mesophyll (photochemistry, biochemistry), rather than by stomatal behavior, as the theoretical relationships worked out by Farquhar and Richards (17) and Francey and Farquhar (18) show.The variability in a '3C around the mean of a given C3 species is just a few parts per thousand. Yet, Farquhar and Richards (17) were able to show a strong correlation between 613C and WUE', in a study on four dwarf wheat varieties, as were Hubick et al. 213www.plantphysiol.org on May 11, 2018 -Published by Downloaded from

Different responses of two contrasting Populus davidiana populations to exogenous abscisic acid application

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Comparative transcriptomics reveals patterns of selection in domesticated and wild tomato

“…We therefore examined whether gene-expression patterns might have been altered during domestication or in response to natural selection by contrasting S. lycopersicum var. M82 and the desert adapted S. pennellii (37)(38)(39)(40). Gene-expression values between S. lycopersicum and S. pennellii were compared across a panel of six tissue types, including root, vegetative, and floral tissues.…”

Physiological and growth responses of Populus davidiana ecotypes to different soil water contents

“…In recent years much attention has been devoted to the study of carbon isotope composition (d 13 C) of plant tissues (Farquhar and Richards, 1984;Martin and Thorstenson, 1988;Osorio and Pereira, 1994;Leroux et al, 1996;Li et al, 2000;Amdt et al, 2001) and d 13 C has been developed as a tool to measure WUE, because a strong correlation is found between d 13 C and WUE (Farquhar et al, 1989). The carbon isotope ratio of plant tissue provides an integrated measurement of internal plant physiological and external environmental properties influencing photosynthetic gas exchange over the time when the carbon was fixed (Anderson et al, 1996;Brodribb and Hill, 1998;Ponton et al, 2002).…”