Reproductive water supply is prioritised during drought in tomato

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.