La^(3＋)缓解碱性盐胁迫引起的西瓜幼苗光合能力下降的作用

Effect of La^(3+) on Alleviation of Decreased Photosynthetic Ability in Alkaline-Stressed Watermelon Seedling

研究了在NaHCO3和Na2CO3共同胁迫下,不同浓度的硝酸镧溶液预处理对西瓜苗叶片光合能力的影响,结果表明,叶面喷施0.1mmol·L-1硝酸镧对碱性盐胁迫下西瓜苗的光合能力下降具有良好的缓解效果,有效减缓了西瓜幼苗叶片叶绿素含量、净光合速率、Mg2+-ATP酶、RuBPCase活性的下降,缓解了碱胁迫对叶片PSⅡ最大光化学效率(Fv/Fm)、光化学猝灭(qP)、实际光化学效率(ФPSⅡ)的抑制,提高了非光化学猝灭(qN),促进了过剩光能的耗散。不同浓度硝酸镧处理对碱性盐胁迫下西瓜苗叶片乙醇酸氧化酶活性没有显著影响,不阻碍光呼吸的进行。而硝酸镧浓度超过一定值时则加重碱胁迫带来的伤害。因此,适宜浓度的硝酸镧预处理可减缓碱性盐胁迫引起的西瓜幼苗光合能力的下降。

The effects of foliar spray of different concentration La（NO3）3 on the photosynthesis under the stress of NaHCO3 and Na2CO3 were studied. Foliar spraying 0.1 mmol·L-1 La（NO3）3 reduced the decrement of photosynthesis,the decrement of leaf chlorophyll content,photosynthesis rate,and the activities of Mg2＋-ATPase and RuBPCase in chloroplast. The application of La（NO3）3 efficiently alleviated the inhibitory effects of alkaline stress on PSⅡmaximum photochemical efficiency（Fv/Fm）,photochemical quenching（qP）and actual photochemical efficiency（ΦPSⅡ）,enhanced the non-photochemical energy dissipation（qN）,promote excessive excitation energy to be consumed. Foliar spray of La（NO3）3 had no effect on glycolic acid oxidase activity,and it did not prevent photorespiration. When the concentration of La（NO3）3 was above a certain level,it aggravated the injury by alkaline stress on watermelon seedlings. These results suggested that the pretreatment of watermelon seedling with proper concentration of La（NO3）3 could decrease the decrement of photosynthesis caused by alkaline stress.