Increasingly intense and earlier heatwaves are not only a concern for humans but also pose significant challenges for plant life. The United Kingdom marked May 25 as its hottest day in May since record-keeping began, only to surpass this temperature record the following day. Unlike humans, who can resort to air conditioning or swimming pools, plants must naturally adapt to rising temperatures and often accompanying droughts. At Penn State, Sarah M. Assmann, Waller Professor of Biology, is delving into how plants respond to environmental cues to develop crops that are more resistant to such stresses.
In a recent discussion, Assmann explored how understanding plant stress responses could enhance crop resilience and contribute to agricultural food security while also potentially mitigating climate warming.
Plant Physiology and Environmental Stress
Assmann: Plants, much like humans, have physiological processes that enable them to sense and react to their environment. Both drought and heat result in water deficits for plants. During droughts, plants struggle to absorb enough water from the soil, and heat causes water to evaporate from the plant. This water loss occurs through tiny pores on the leaves called stomata.
When plants lose water through stomata, it’s akin to humans sweating — water evaporates from our skin to help cool us down, and plants use a similar mechanism. However, when heat and drought occur simultaneously, plants face a dilemma: how to stay cool while retaining sufficient water for other vital processes? The regulation of stomatal size, controlled by guard cells, becomes crucial. These cells detect heat and drought through hormonal signals, adjusting the stomata to balance water retention and cooling needs.
In dry conditions, plants increase a hormonal signal known as abscisic acid, prompting the stomata to close slightly to reduce water loss, though this also limits cooling and carbon dioxide intake for photosynthesis. Plants exhibit complex responses to optimize this balance, adjusting stomatal openings within seconds to minutes.
Adapting to a Changing Climate
Assmann: While some plants manage this physiological balancing act well, many do not, adversely affecting crop yields. Key crops such as wheat and rice are anticipated to see global yield declines. Therefore, enhancing crop resilience to extreme weather is a priority. Our research focuses on rice, a staple for half the world’s population, exploring whether certain rice varieties are better adapted to withstand heat and drought. By integrating these traits into popular varieties, we aim to bolster crop performance in future climates.
The Importance of Water Management
Assmann: Rice, in particular, demands significant water, nearly twice that of most other crops. In areas with ample water, rice fields are typically flooded, ensuring the plants receive enough water. However, for farmers without irrigation access, rice cultivation depends heavily on rainfall. Our work investigates how to maintain rice yields with less water. We are evaluating which rice varieties thrive with limited water, potentially reducing the need for irrigation and making cultivation more accessible.
Additionally, reducing irrigation can lower fuel use for irrigation equipment, thus decreasing greenhouse gas emissions. Traditional flooding of rice fields creates anaerobic conditions that promote methane-producing microorganisms, further contributing to global warming. By developing rice that requires less water or shorter periods of water access, we can help mitigate the impacts of global warming.
Original Story at www.psu.edu