钾肥种类及用量对低温胁迫下苜蓿根颈含氮保护物质含量及抗寒性的影响

Effects of Potassium Fertilizer Types and Amounts on Nitrogen Protective Substances in Alfalfa Root Crown and Cold Resistance under Low Temperature Stress

为探讨钾肥种类及用量对低温胁迫下苜蓿(Medicago sativa L.)越冬器官抗寒性的影响及含氮保护物质变化的生理机理,对苜蓿施用氯化钾、硫酸钾和磷酸二氢钾3种钾肥,设置0、100、200和300 kg/hm^(2) K_(2)O 4个用量处理,于越冬前取苜蓿越冬器官带回室内模拟4℃、-10℃、-20℃和-30℃低温胁迫处理,测定相对电导率、可溶性蛋白、脯氨酸和游离氨基酸含量,并进行相关性分析。结果表明:苜蓿根颈相对电导率随着温度的降低持续增长,游离氨基酸含量的变化趋势与之相反,其他指标则随着温度的降低表现为先升高后降低的趋势。3种钾肥处理的相对电导率随着施肥量的增加先降低后增长,其他指标均表现为先升高后降低的趋势;且在不同的低温胁迫处理下,以硫酸钾处理的苜蓿根颈相对电导率最低,其他指标含量最高,且在施用量为200 kg/hm^(2)K_(2)O时,苜蓿根颈相对电导率最低,较CK减少了23.37%~38.02%,可溶性蛋白、脯氨酸和游离氨基酸含量最高且均显著高于CK(P<0.05),分别增长了32.48%~50.39%、43.95%~264.29%和56.50%~249.50%,说明施用硫酸钾种类钾肥200 kg/hm^(2) K_(2)O更有利于减缓苜蓿细胞液外渗程度,调节细胞渗透势,保护生物膜,提高苜蓿抗寒性。

This study aimed to investigate the effects of potassium fertilizer types and amounts on the cold resistance of overwintering organs of alfalfa(Medicago sativa L.)under low temperature stress and the physiological mechanism of changes in nitrogen-containing protective substances.Potassium chloride,potassium sulfate and potassium dihydrogen phosphate were applied to alfalfa in four dosage treatments of 0,100,200 and 300 kg/hm^(2) K_(2)O.The overwintering organs of alfalfa were taken back to the room before wintering to simulate low temperature stress treatments at 4℃,-10℃,-20℃and-30℃.The relative electrical conductivity,soluble protein,proline and free amino acid contents were determined,and their correlations were examined.The results showed that as the temperature decreased,the relative electrical conductivity of alfalfa root crown increased,yet the free amino acid content had a different pattern of behavior,with other indicators fluctuating between an increase and a decrease.The relative electrical conductivity of the three potassium fertilizer treatments decreased and then increased with increasing fertilizer application,while other indicators showed a trend of increasing and then decreasing.Under different low temperature stress treatments,the lowest relative electrical conductivity of alfalfa root crown and the highest content of other indicators were found in the potassium sulfate treatment.At an application rate of 200 kg/hm^(2) K_(2)O,the relative electrical conductivity of alfalfa root crown was the lowest(P<0.05),with a decrease of 23.37%to 38.02%compared to CK,and the soluble protein,proline and free amino acid contents were the highest(P<0.05),with increase of 32.48%to 50.39%,43.95%to 264.29%and 56.50%to 249.50%,respectively.The above results indicated that the application of potassium sulfate(200 kg/hm^(2) K_(2)O)was more beneficial to slow down the extravasation of alfalfa cell fluid,regulate cell osmotic potential,protect biofilm,and improve the cold resistance of alfalfa.