Abstract
Reproductive success largely defines the fitness of plant species.
Understanding how heat and drought affect plant reproduction will thus
be key to predicting future plant fitness under rising global
temperatures. Recent work suggests reproductive tissues are highly
vulnerable to water stress in perennial plants where reproductive
sacrifice could preserve plant survival. However, most crop species are
annuals where such a strategy would theoretically reduce fitness. We
examined the reproductive strategy in tomato (Solanum lycopersium) to
determine whether water supply to fruits was prioritized above
vegetative tissues during drought. Using optical methods, we map xylem
cavitation and tissue shrinkage in vegetative and reproductive organs
during dehydration to determine the priority of water flow under acute
imposed water stress. Stems and peduncles of tomato showed significantly
greater resistance to xylem cavitation than vegetative tissues. This
prioritization of reproductive water supply enabled tomato fruit to
continue expanding during acute water stress, utilising xylem water made
available by capacitance and cavitation of vegetative tissues. Here,
tomato plants prioritize water supply to reproductive tissues,
maintaining fruit development in drought conditions. These results
emphasize the critical role of water transport in shaping tomato life
history and suggest a broad relevance of hydraulic prioritization in
plant ecology.