碱胁迫对黑麦草幼苗根系活性氧代谢和渗透溶质积累的影响

为了探讨牧草对碱胁迫的耐受程度，采用营养液砂培方法，研究了不同浓度NaHCO3（0、50、100、150和200 mmol·L^-1）胁迫对黑麦草幼苗根系生长、活性氧代谢和渗透溶质积累的影响。结果表明：NaHCO3胁迫显著抑制黑麦草幼苗根系的生长，其抑制程度随胁迫浓度提高而增强，黑麦草可耐受的最高NaHCO₃浓度约为150 mmol·L^-1。随着NaHCO₃胁迫浓度的增加，黑麦草根中超氧阴离子(O^-·₂)、过氧化氢(H₂O₂)和丙二醛(MDA)含量明显上升，超氧化物歧化酶(SOD)活性和谷胱甘肽(GSH)含量显著下降，过氧化氢酶(CAT)、过氧化物酶(POD)和抗坏血酸过氧化物酶(APX)活性及抗坏血酸(ASA)含量先升后降。黑麦草根中Na⁺含量随NaHCO₃浓度增大而增加，K⁺含量和K⁺/Na⁺比降低，可溶性糖含量先升后降，脯氨酸含量则先降后升，游离氨基酸含量呈先升后降再升高变化。表明碱胁迫导致的活性氧代谢失调和Na⁺、K⁺失衡及积累有机溶质进行渗透调节时更多能量的消耗可能是黑麦草根系生长受抑的重要因素。

Effects of Alkaline Stress on the Metabolism of Reactive Oxygen Species and Osmotica Accumulation in Ryegrass Seedling Roots

To explore the tolerant extent of ryegrass seedlings to alkaline stress, ryegrass seedlings were exposed to Hoagland’s nutrient solution with NaHCO₃ added (0, 50, 100, 150, 200 mmol·L^-1), and the effects of NaHCO₃ stress on the growth of roots, metabolism of reactive oxygen species (ROS) and osmotica accumulation in roots were studied by a sandy culture in greenhouse. The results showed: Alkaline stress had significantly inhibitory effects on the roots growth of ryegrass seedlings, the inhibition was aggravated with the increasing of NaHCO₃ concentration, the maximum concentration for ryegrass in resistance to alkaline stress was 150 mmol·L^-1. With increasing NaHCO₃ stress, the contents of O^-·₂, H₂O₂ and MDA in the seedling roots increased dramatically, superoxide dismutase (SOD) activity reduced and glutathione (GSH) contents decreased significantly, the activities of catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) as well as ascorbic acid (AsA) content first increased and then decreased. The root Na⁺ content increased significantly with increasing NaHCO₃ concentration, while root K⁺ content and K⁺/Na⁺ ratio were in adverse, soluble sugar content first increased and then decreased, proline content first decreased and then increased, free amino acid content first increased, then decreased and increased again. All the above results indicated that alkaline stress caused the imbalance of ROS metabolism and the disturbance of Na⁺ and K⁺ homeostasis in the roots of ryegrass seedlings, and consumed more energy for osmotic adjustment by accumulating organic solutes, which might partly lead to its growth inhibition under alkaline stress.