Abstract:

On the basis of the knowledge that silicon can improve the resistance of plants, effects of silicon on the germination and physiology of alfalfa(Medicago satiava L.‘Sadie7’)were studied under the PEG drought simulation using a laboratory experiment. The regulation mechanism of silicon fertilizer on the drought resistance of alfalfa was preliminarily investigated in order to find out suitable concentration of silicon fertilizer to improve the drought resistance of alfalfa effectively. The results showed that under certain drought level, suitable silicon concentration increased alfalfa germination rate, germination potential, radicle length, peroxidase (POD), superoxide dismutase (SOD), catalase (CAT) and reduced malondialdehyde (MDA) content. Under 10% PEG stress, application of 1.00 mmol·L^-1 potassium silicate significantly increased the germination potential and germination rate of alfalfa seeds. When potassium silicate concentration reached 2.50 mmol·L^-1, it inhibited germination. At 10% and 15% PEG concentrations, the radicle length of 1.00 mmol·L^-1 treated silicon was significantly higher (P<0.05) than that of the control. Under the stress of 5% and 10% PEG, 2.00 mmol·L^-1 of potassium silicate treatment significantly increased alfalfa seedlings superoxide dismutase (SOD) activity; at the concentration of 15% PEG, 2.50 mmol·L^-1 of potassium silicate significantly decreased the content of malondialdehyde (MDA) content, and increased the activity of peroxidase (POD) and catalase (CAT). According to the different degrees of drought stress, the suitable silicon treatment concentration to improve the drought resistance of alfalfa was different.Our results indicated that silicon fertilizer plays an important role since the seed germination of alfalfa and rescues physiological and bioohemical processes during drought stress.

Key words: Alfalfa, Drought stress, Silicon, Germination, Physiological characteristics

摘要：

在已知硅能提高植物抗逆性的基础上，采用实验室发芽法研究PEG干旱模拟下，硅对紫花苜蓿（Medicago satiava L.‘Sadie7’）萌发及生理的影响。初步探讨硅肥对紫花苜蓿抗旱性的调控机制，以期筛选出有效提高紫花苜蓿抗旱性的适宜硅肥浓度。结果表明：在一定干旱程度和适宜硅浓度下，紫花苜蓿种子发芽率、发芽势和胚根长有所提高，过氧化物酶（POD）、超氧化物歧化酶（SOD）和过氧化氢酶（CAT）活性增加，而丙二醛（MDA）含量降低。在10% PEG胁迫下，施用1.00 mmol·L^-1硅酸钾显著提高紫花苜蓿种子发芽势和发芽率，当硅酸钾浓度达到2.50 mmol·L^-1时会抑制其发芽。在10%和15% PEG浓度下，1.00 mmol·L^-1硅酸钾处理后胚根长显著（P<0.05）大于对照。在5%和10% PEG胁迫下，2.00 mmol·L^-1硅酸钾处理显著提高了紫花苜蓿幼苗超氧化物歧化酶（SOD）活性；在15% PEG浓度下，2.50 mmol·L^-1硅酸钾处理显著降低了幼苗丙二醛（MDA）含量，且提高过氧化物酶（POD）活性和过氧化氢酶（CAT）活性。干旱胁迫程度不同，所适宜的能提高紫花苜蓿抗旱性的硅酸钾浓度不同。研究表明，硅从紫花苜蓿种子萌发开始就作用其生理生化过程，并且提高其抗逆性。

关键词: 紫花苜蓿, 干旱胁迫, 硅肥, 萌发, 生理特性