低温胁迫对紫花苜蓿叶片叶绿素荧光特性的影响

以经过抗寒锻炼的盆栽不同抗寒紫花苜蓿(Medicago sativa L.)品种为材料,分别在室温和低温处理后(-8℃)测定不同秋眠型紫花苜蓿品种的叶绿素荧光参数,分析低温对不同苜蓿品种的冷害指数和叶绿素荧光参数的影响。结果表明:在低温胁迫后非秋眠型Dona Ana和Pierce的PSⅡ最大光化学效率(F_v/F_m)显著降低,电子传递速率(ETR)减慢,实际光化学量子产量(Y)下降,叶片受低温胁迫较重;秋眠型Vernal和5246各荧光参数变化不大,而非秋眠型CUF101、极非秋眠型UC-1465非光化学淬灭(NPQ)值显著升高(P<0.05),其他的参数变化较小。低温胁迫很轻时,非光化学淬灭系数NPQ升高,说明耗散过剩的光能具有保护光合机构的作用。因此紫花苜蓿各荧光参数的变化与其抗寒特性密切相关。

Influence of Chlorophyll Fluorescence Characteristics on Alfalfa Seedlings under Cryogenic Stress

Chlorophyll fluorescence parameters were measured in alfalfa varieties with different fall dormancy under room temperature and low temperature(-8℃),respectively.The influence of low-temperature on chilling index and the chlorophyll fluorescence parameters were analyzed in different alfalfa varieties.Results show that after cryogenic stress,maximum photochemical efficiency(Fv/Fm) of PS Ⅱ in both Dona Ana and Pierces varieties decreases significantly.Electron transfer rate(ETR) and actual photochemical quantum yield(Y) decreased suggesting that the leaves of both cultivars suffer heavier cold injury.There were small change of fluorescent parameters for Vernal and 5246.The non-photochemical quenches(NPQ) value increases significantly in non-fall dormancy varieties(CUF101 and UC-1465),but other parameters show no significant change.Under light cryogenic stress,non-photochemical quenches(NPQ) value increased suggesting that the dissipation of excess light energy is conducive to protecting photosynthetic apparatus.Therefore fluorescence parameters of alfalfa varieties are closely related with cold resistance.