Drought stress is arguably one of the most important stresses in terms of its effects on plant growth and in our case, food supply. Drought stress occurs when a plant does not have enough water for an extended period of time. Plants such as trees and crops have a vascular system – analogous to the human vascular system, plants draw in water and nutrients through a series of tubes (called xylem and phloem). A plant needs a continuous source of water to keep water and nutrients flowing though the plant. Without enough water, an air bubble forms (called an embolism), causing the upper parts of a plant to dry out and eventually die under drought stress.
So why does this matter? Well agriculture is very water intensive and drought can be very bad for food production. However during a drought scenario, when a farmer may have limited water reserves, being able to tell when a plant is drought-stressed could mean the difference between saving year’s crop yield with targeted irrigation and losing it. Using sunflowers, Marchand et al. (Marchand et al. 2013. Plant, Cell and Environment 36:2175-2189) set out to find a biomarker for drought stress – a signal that could be used to detect when a plant starts to become drought stressed. The authors looked at the expression levels of many genes and compared them to different measures of drought stress currently used (e.g. the amount of water in soil).
The authors found that they could analyze three genes to reliably determine if a sunflower was drought stressed, however due to the length of time from sampling the plant to getting the results, their technique does not allow pre-emptive watering to reduce drought stress. This is a down-side, but let’s look at the implications.
Having a biomarker for drought stress would allow farmers to breed better plants by selecting for plants that better resist drought stress. On top of this, technological advancement might allow the technique to be used in pre-emptive watering, provided the genetic analysis could be sped up. This research highlights one of the many ways that plant scientists are working to make a more sustainable and secure food supply: by using science to select the best crops and determine the best time(s) and way(s) to use our limited resources.
Stay safe and stay informed,