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Effects of exogenous NO on growth and physiological characteristics of watermelon seedlings under aluminum stress
Received:February 03, 2021  
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KeyWord:watermelon;NO;stress of aluminum;physiological characteristics;nutrient content
Author NameAffiliationE-mail
XIAO Jiachang College of Horticulture, Sichuan Agricultural University, Chengdu 611130, China  
ZHENG Kaimin College of Horticulture, Sichuan Agricultural University, Chengdu 611130, China  
MA Junying College of Horticulture, Sichuan Agricultural University, Chengdu 611130, China  
ZHENG Yangxia College of Horticulture, Sichuan Agricultural University, Chengdu 611130, China 754924349@qq.com 
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Abstract:
      To alleviate the effect of exogenous NO on aluminum stress in watermelon, the effects of different concentrations of exogenous nitroprune(SNP) (50, 100, 200, and 500 μmol·L-1) on the growth and physiological characteristics of watermelon seedlings under high concentrations of aluminum stress(1 200 μmol·L-1) were studied using the Zaojia 84-24 watermelon variety as experimental material and SNP as NO donors. The results showed that the watermelon seedling growth under aluminum stress was depressed; watermelon leaf cell membrane permeability increased significantly; the product of membrane lipid peroxide malondialdehyde(MDA) increased by 14.18%; superoxide dismutase(SOD), peroxidase(POD), and catalase(CAT) levels were significantly reduced; and soluble sugar and proline contents increased noticeably. Aluminum stress led to a significant decrease in chlorophyll content in leaves and affected the content of nutrient elements in watermelon leaves, resulting in a significant accumulation of aluminum ions; this eventually led to a decline in the photosynthetic rate and the seedling's weakened photosynthetic capacity. After the addition of exogenous NO(50 μmol·L-1), the aluminum toxicity of watermelon was alleviated; the MDA content in the leaves was significantly decreased by 12.64%; the contents of SOD, POD, and CAT were increased; and the proline content was significantly increased, to regulate the metabolism of reactive oxygen species and maintain the stability of cell structure and function. Moreover, the accumulation of aluminum in leaves was significantly decreased. The chlorophyll content in leaves was increased, significantly enhancing the photosynthetic capacity of watermelon seedlings. When the concentration of NO was 500 μmol·L-1, it had a toxic effect on watermelon, and the biomass of aboveground and underground parts decreased by 28.26% and 3.57%, respectively, indicating that the duality effect of NO. Aluminum stress inhibited watermelon growth, antioxidant enzymes, osmotic regulatory substances, photosynthetic parameters, and other physiological characteristics. At the same time, the appropriate external application of NO could alleviate the physiological damage of watermelon under aluminum stress and promote the growth of watermelon seedlings.