What if the secret to drought-resistant crops isn't how much water plants use, but when they use it? A new study identifies a daily window that could help breeders develop tomatoes that better withstand drought without sacrificing yield.

A hidden daily rhythm inside tomato plants could help scientists develop crops that produce higher yields while using less water, according to new research from the Hebrew University of Jerusalem.

The study, led by Dr. Sanbon Chaka Gosa and Prof. Menachem Moshelion from the Faculty of Agriculture at the Hebrew University of Jerusalem, found that the timing of when tomato plants open and close their microscopic leaf pores may be just as important as the number of pores they possess.

The findings could give plant breeders a powerful new way to identify drought-resilient crops as climate change places increasing pressure on agriculture.

Published in Plant Science, the research focused on stomata, tiny pores that allow plants to absorb carbon dioxide for photosynthesis while also losing water through transpiration. Instead of relying on traditional single-point measurements, the researchers continuously monitored whole-plant water use, allowing them to capture how plants respond to changing environmental conditions throughout the day.

The team combined years of field performance data with advanced greenhouse phenotyping to compare drought response across genetically diverse tomato lines. They found that the strongest-performing plants consistently displayed an early-morning surge in stomatal activity; opening their stomata when sunlight was already strong but before heat and dry air greatly increased water loss.

The researchers describe this period as a physiological "golden hour," during which plants maximize photosynthesis while minimizing unnecessary water loss.

"Plants don't simply save water during drought, they manage it strategically," said Prof. Moshelion. "Understanding these dynamic patterns gives breeders entirely new traits to target when developing crops that can thrive under increasingly unpredictable climate conditions."

The study also showed that the best-performing tomato lines recovered more quickly after drought and maintained high biomass and water-use efficiency. Surprisingly, plants that used more water under favorable conditions were often the ones that bounced back most effectively once water returned.

The researchers found that while high-performing plants tended to have more stomata on the underside of their leaves, anatomy alone could not predict drought resilience. Instead, continuous measurements of how plants regulate water throughout the day proved far more informative.

"Our work shows that a plant's daily rhythm matters," said Dr. Gosa. "By measuring how plants respond continuously rather than at a single moment, we can identify resilient varieties much earlier and with far greater precision."

The researchers believe the approach could significantly shorten the time needed to identify promising crop varieties, helping breeders develop plants that can better withstand drought while maintaining productivity. Beyond tomatoes, they say the same strategy could be applied to other crops as agriculture adapts to a warmer, drier future.