Plants have several strategies for protecting themselves from dehydration. “First of all, they close the stomata on their leaves to reduce transpiration,” says Johannes Liesche, head of the Plant Cell and Stress Biology Research Group at the University of Graz. This means that significantly less water escapes, but also that hardly any CO2 is taken up for photosynthesis. “As a result, the plant produces less sugar and its productivity declines. The remaining energy is increasingly channelled into root growth to penetrate deeper, moister layers,” explains the researcher.
During prolonged drought, the entire life cycle adapts. The growth phase is shortened. “Depending on when the drought occurs, many plants flower earlier or for a shorter period and form seeds more quickly to give the next generation a chance,” says Liesche. Fruits remain smaller or fail to form at all.
Some plants cope better with drought than others. “Vines root up to six metres deep and can thus still reach water, even if it hasn’t rained for a long time,” the researcher gives as an example, adding: “Others reduce transpiration through small, thick, leathery leaves. In some, the stomata are situated deeper and are thus sheltered from the wind, which further reduces evaporation.
Furthermore, plants adapt to changing environmental conditions through molecular mechanisms. These alter the composition of cell membranes and cytoplasm to maintain structural integrity. New findings in this area are of high interest, particularly with regard to the breeding of drought-resistant varieties for agriculture.
In a project, Liesche and his research group investigated how molecular signalling pathways can be fine-tuned so that a plant reacts more quickly or strongly to drought. For the scientist, genetic engineering is anything but a bogeyman: “With new genomic technologies (NGT), the plant’s own genes are modified. This also happens in traditional breeding. The advantage of NGT is that the desired characteristics of a plant can be achieved more quickly. But the result is essentially the same.” The researcher is convinced: “If we want our familiar food in future, there is no way around plant breeding with NGT.”
The research team behind the KLIWAS – Water in a Changing Climate study, which is funded by the Ministry of Agriculture, also highlights the need to place greater emphasis on drought-resistant varieties in agriculture in future.