Exogenous melatonin alleviates the physiological effects of drought stress in sweet sorghum seedlings

doi:10.11686/cyxb2022340

Abstract

Abstract:

In order to explore the possible physiological mechanism of exogenous melatonin alleviation of drought stress in sweet sorghum seedlings， a pot experiment was set up to investigate the effects of spraying melatonin （100 μmol·L^-1） on the growth and physiological characteristics of ‘Dalish’ sweet sorghum seedlings under natural drought conditions. It was found that drought stress resulted in water imbalance in plant shoots， damaged the chloroplast structure and produced intracellular oxidative stress， which significantly inhibited the growth of the sweet sorghum seedlings. Spraying 100 μmol·L^-1melatonin significantly reduced the malondialdehyde content in leaves， facilitated increased accumulation of soluble protein and proline， increased the water content of leaves， promoted orderly arrangement of the granula lamellae of chloroplast， and increased the content of photosynthetic pigment. Spraying melatonin also significantly increased the activities of peroxidase and nitrate reductase in leaves. In conclusion， spraying 100 μmol·L^-1 melatonin enhanced the protective effect of antioxidant systems in sweet sorghum leaves under drought conditions， which helped to maintain plant water balance， improve chloroplast structure and increase the photosynthetic pigment content through osmotic regulation and synergistically enhanced nitrogen metabolism. At the same time， exogenous melatonin enhanced nitrogen metabolism and promoted the plant growth， resulting in alleviation of drought damage to sweet sorghum seedlings.

Key words: sweet sorghum, drought stress, melatonin, physiological mechanism

Jia LIANG, Zhao-yang HU, Zhi-ming XIE, Liu-feng MA, Yun CHEN, Zhi-gang FANG. Exogenous melatonin alleviates the physiological effects of drought stress in sweet sorghum seedlings[J]. Acta Prataculturae Sinica, 2023, 32(7): 206-215.

Figures/Tables 8

Table 1 Effects of exogenous melatonin on growth of sweet sorghum seedlings under drought stress

处理 Treatment	株高 Plant height （cm）	茎粗 Stem diameter （mm）	叶面积 Leaf area （cm²）	地上部干重 Shoot dry weight （g·plant^-1）	根系干重 Root dry weight （g·plant^-1）
CK	97.83±3.95a	4.46±0.29a	23.12±0.97a	0.49±0.07ab	0.10±0.02ab
D	73.83±6.52b	3.59±0.35c	15.05±1.36b	0.42±0.05b	0.06±0.02b
CK+MT	98.01±2.31a	4.45±0.15ab	24.60±1.57a	0.49±0.04a	0.11±0.01a
D+MT	85.65±10.60ab	3.91±0.24bc	22.40±1.98a	0.48±0.13ab	0.08±0.03ab

Fig.1 Effects of exogenous melatonin on leaf relative water content of sweet sorghum seedlings under drought stress

Table 2 Effects of exogenous melatonin on chlorophyll and carotenoid contents and their ratios in sweet sorghum seedlings under drought stress

项目 Item	处理 Treatment
项目 Item	CK	D	CK+MT	D+MT
叶绿素a Chlorophyll a （Chl a）	10.09±0.47a	5.69±0.36c	9.19±0.23b	8.92±0.48b
叶绿素b Chlorophyll b （Chl b）	4.00±0.52a	2.72±0.38b	4.00±0.53a	3.55±0.42ab
总叶绿素Total chlorophyll （T-Chl）	14.10±0.72a	8.42±0.41c	13.20±0.71ab	12.47±0.14b
类胡萝卜素Carotenoid （Car）	1.66±0.11a	0.85±0.12c	1.41±0.48ab	1.02±0.10bc
Chl a/Chl b	2.55±0.37a	2.12±0.36a	2.32±0.26a	2.55±0.41a
T-Chl/Car	8.57±0.98a	9.96±1.44a	10.20±3.78a	12.30±1.42a

Fig.2 Effects of exogenous melatonin on chloroplast ultrastructure in leaves of sweet sorghum seedlings under drought stress

Fig.3 Effects of exogenous melatonin on MDA contents and relative conductivity of sweet sorghum seedlings under drought stress

Fig.4 Effects of exogenous melatonin on osmotic adjustment substances of sweet sorghum seedlings under drought stress

Fig.5 Effects of exogenous melatonin on nitrate reductase activity of sweet sorghum seedlings under drought stress

Fig.6 Effects of exogenous melatonin on antioxidant enzyme activities of sweet sorghum seedlings under drought stress

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