Measuring and alleviating drought stress in pea and lentil
¹Institute of Bioenergy Crops and Sugar Beet National Academy of Agrarian Sciences of Ukraine, 25 Klinichna Str., UA03110 Kyiv, Ukraine
²Poltava State Agrarian University, 1/3 Skovorody Str., UA36003 Poltava, Ukraine
³Uman National University of Horticulture, 1 Instytutska Str., UA20305 Uman, Ukraine
Water deficit in the soil can cause drought stress in plants and drastically affect plant growth and crop yield. Therefore, early detection of drought stress in plants followed by the timely application of agronomic measures to alleviate plant conditions is crucial. This research aimed to study the agronomic practices that could reduce the sensitivity of pea and lentil to drought stress. The practices included (i) soil amendment with moisture retainer (hydrogel), (ii) seed treatment with a growth regulator to promote root formation, (iii) application of a biological formulation to boost soil mycorrhizal biota, and (iv) foliar application of micro fertilisers. The research was carried out in Ukraine in 2015−2020. Drought stress in plants was detected by measuring chlorophyll fluorescence with a portable fluorometer Floratest and calculating the ratio of variable to maximum fluorescence Fv/Fm of the photosystem. The content of proline, high values of which in vegetative organs point out to stress in plants, was determined by colorimetric analysis using ninhydrin.
In pea, the incorporation of hydrogel (Aquasorb) and growth regulator (Mycofriend) combined with seed treatment (Kelpak SC) and foliar application of micro fertiliser (Biovit or Freya-Aqua Legumes) at BBCH 14 led to obtaining Fv/Fm values from 0.81 to 0.82. Similarly in lentil, the maximum value of Fv/Fm (0.67) was obtained with the application of all studied agronomic practices, with the correlation coefficient between yield and Fv/Fm at the flowering stage (BBCH 61) r = 0.97. In pea, the correlation between yield and Fv/Fm at the budding stage (BBCH 51) was r = 0.99. The content of proline in photosynthetic plant organs was species-specific; however, in the control treatment, where plants were exposed to drought, its maximum value was 1.10 μmol g-1 in pea and 1.40 μmol g-1 in lentil, while with the application of the proposed agronomic practices proline content was only 0.56 μmol g-1 in pea and 0.36 μmol g-1 in lentil. Obtained strong correlation between proline content in plant vegetative organs and the ratio of variable to maximum fluorescence Fv/Fm of the plant photosystem indicates that measurement of Fv/Fm with portable fluorometer might be an effective method of early identification of drought stress in pea and lentil.