Effects of exogenous Strigolactone on the physiological and ecological characteristics of Pennisetum purpureum Schum. Seedlings under drought stress

Abstract

Background: Drought is one of the main environmental factors limiting plant growth and development. Pennisetum purpureum Schum. was used to explore the mitigation effects of exogenous strigolactone (SL) on drought stress during the seedling stage. The effects of different concentrations (1, 3, 5, and 7 μmol·L^{- 1}) of SL on the photosynthesis characteristics, growth performance, and endogenous abscisic acid (ABA) of P. purpureum under drought stress were studied.

Results: Exogenous SL could effectively alleviate the inhibitory effect of drought stress on P. purpureum growth. Compared with drought stress, the net photosynthesis rate, stomatal conductance, transpiration rate, and water-use efficiency of the leaves of P. purpureum after SL treatment significantly increased, thereby exerting a significant mitigation effect on the decrease in photosystem II maximum photochemical efficiency and the performance index based on light absorption caused by drought. Moreover, the exogenous application of SL can effectively increase the fresh and dry weight of the leaves and roots and the main-root length. After applying SL for 120 h, the ABA content of P. purpureum decreased significantly. The activity of key enzymes of photosynthesis significantly increased after 48 h of external application of SL to P. purpureum.

Conclusions: SL treatment can improve the photosynthesis performance of P. purpureum leaves under drought conditions and increase the antioxidant capacity of the leaves, thereby reducing the adverse effects of drought, promoting the growth of P. purpureum, and effectively improving the drought resistance of P. purpureum.

Keywords: Drought stress; Endogenous ABA; Growth performance; Pennisetum purpureum Schum; Photosynthesis characteristics; Strigolactone.

Fig. 1

Effect of spraying SL on the physiological characteristics of Chl fluorescence of P. purpureum leaves under drought stress. Effects of SL on Fv/Fm (a, b, and c) and PIabs (d, e, and f) of P. purpureum leaves. Different lowercase letters at the same time indicate significant differences (P < 0.05). N: normal watering treatment; D: drought stress treatment only; T1, T2, T3, and T4 represent the different treatment concentrations of SL under drought stress (1, 3, 5, and 7 μmol·L^− 1 respectively)

Fig. 2

Effect of spraying SL on the root length of P. purpureum under drought stress. Effects of SL on root length (a, b, and c) of P. purpureum. Different lowercase letters at the same time indicate significant differences (P < 0.05). N: normal watering treatment; D: drought stress treatment only; T1, T2, T3, and T4 represent the different treatment concentrations of SL under drought stress (1, 3, 5, and 7 μmol·L^− 1 respectively)

Fig. 3

Effect of spraying SL on the ABA content of P. purpureum under drought stress. Effects of SL on leaf ABA content (a, b, and c) and root ABA content (d, e, and f) of P. purpureum. Different lowercase letters at the same time indicate significant differences (P < 0.05). N: normal watering treatment; D: drought stress treatment only; T1, T2, T3, and T4 represent the different treatment concentrations of SL under drought stress (1, 3, 5, and 7 μmol·L^− 1 respectively)

Fig. 4

Effect of spraying SL on the activities of key enzymes in the photosynthesis of P. purpureum under drought stress. Effects of SL on NADP-ME (a), PEPC (b), and PPDK (c) activities of P. purpureum. Different lowercase letters at the same time indicate significant differences (P < 0.05). N: normal watering treatment; D: drought stress treatment only; T1, T2, T3, and T4 represent the different treatment concentrations of SL under drought stress (1, 3, 5, and 7 μmol·L^− 1 respectively)