Drought-Defying Discovery: Plants Keep Growing with Less Water

In an era marked by the escalating threat of global drought, the quest for drought-resistant crops has become more critical than ever. Recent groundbreaking research by scientists from the Australian National University (ANU) and James Cook University (JCU) has unveiled a promising mechanism that could revolutionize crop breeding. Published in the journal *Nature Plants*, this discovery reveals a natural process in some plants that allows them to limit water loss without significantly affecting carbon dioxide (CO2) intake, thereby maintaining their growth and productivity even under water-scarce conditions.

Plants typically close tiny pores on their leaves, known as stomata, to prevent excessive water loss during hot days. However, this defensive action also halts photosynthesis because CO2, essential for this process, cannot enter the leaves. For years, plant scientists have sought a way to enable plants to continue CO2 uptake while minimizing water loss. The team led by Dr. Suan Chin Wong from ANU and Dr. Diego Marquez, now a Research Fellow at the Busch Lab at the University of Birmingham, has made a significant stride towards this goal.

The researchers have identified a mechanism in some plants that restricts water loss without closing the stomata, thus allowing the plants to continue photosynthesis and growth. Dr. Marquez explains that the team is now delving into three major research areas related to this ‘non-stomatal control’ of transpiration in C3 plants, a group that includes most crops. The first area focuses on understanding how widespread this mechanism is across different plant groups and environments. The second area investigates the cellular structures involved, while the third examines the internal plant signaling that controls the mechanism.

Dr. Nicole Pontarin at ANU is leading the study on cellular structures, collaborating with Dr. Lucas Cernusac at JCU, who is researching the ecological scale of the phenomenon. According to Marquez, the team suspects that aquaporins, a family of small, integral membrane proteins found in animal and plant cells, may play a crucial role in this mechanism. Aquaporins consist of helical segments and a narrow pore, among other features, and are known to facilitate water transport within cells.

To shed more light on their discovery, Marquez elaborates on the process of transpiration, which involves the movement of water from the soil through the roots, up to the leaves, and finally evaporating through the stomata. Within the leaf, water travels through the mesophyll, where photosynthesis occurs. While some water and CO2 are used in photosynthesis, the remaining water evaporates through the stomata, and CO2 moves in the opposite direction, entering the stomata and moving into the mesophyll.

The newly discovered mechanism, however, restricts water loss before it reaches the stomata, thereby allowing the plant to continue CO2 uptake without closing the stomata. This means the plant can restrict water loss without halting growth. Marquez notes that the reasons behind this selective water restriction will become clearer once the responsible structures are identified and studied.

The next significant step for the research team is to identify the genes involved in expressing this trait. Marquez believes that exploiting this mechanism in crop development could be feasible, either through variety selection or genetic modification. However, he emphasizes that more research and investment, whether public or private, are necessary to achieve these ambitious objectives.

As the research progresses, Marquez is also investigating whether non-stomatal control of transpiration occurs in C4 plant species of agricultural interest and hopes to publish results soon. Additionally, he is applying for funding to explore the signaling and environmental triggers that control this phenomenon.

This discovery holds immense potential for developing drought-resistant crops, offering a glimmer of hope for agriculture in the face of climate change and water scarcity.

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