增强的UV-B辐射对黄瓜(Cucumis sativus)不同叶位叶片生长、光合作用和呼吸作用的影响

EFFECTS OF ENHANCED ULTRAVIOLET-B RADIATION ON GROWTH, PHOTOSYNTHESIS AND RESPIRATION OF CUCUMIS SATIVUS LEAVES ON DIFFERENT POSITIONS

在植物生长室中 ,黄瓜植株第 1片真叶出现后 ,用人工UV B光源照射 6 0d ,测定植物各叶位叶片的生长和生理活动 .结果表明 ,UV B辐射条件下 ,植物出叶时间被延迟 ;叶面积和叶干重下降 ,降幅与叶位高低正相关 ;叶片含水量降低 ,老龄叶片 (第 1叶 ,下位叶 )和幼龄叶片 (第 5叶 ,上位叶 )的水分降幅均高于成年叶片 (第 3叶 ,中位叶 ) ;叶片的伸展速度、叶片数目以及单叶面积减少 ,致使黄瓜总叶面积下降 ;植株节间长度缩短 ,是植株矮化的重要原因 ;根、茎、叶等器官之间的相关生长变化不大 ,叶片生长在其中起重要的协调作用 .UV B降低Pn和EAQE,对光合作用的抑制程度随叶位升高而增加 .UV B辐射后 ,黄瓜叶片的光呼吸显著提高 ,增幅与叶片发育阶段有关 .UV B对黄瓜第 1叶的暗呼吸没有影响 ,第 2、3叶略微下降 ,第 4叶显著升高 .分析认为 ,植株矮化和叶面积减少有利于植物适应UV B辐射 ;水分含量和光合作用减少、呼吸作用增强是黄瓜生长受抑制的生理基础 .图 2表 2参

The growth and physiological variation of cucumber grown under UV B radiation for 60 d in plant growth chamber were monitored. The results showed that the leaf emergence was delayed, the reduced magnitudes of leaf area and dry weight were positively correlative to leaf position. The reduced magnitude of water content in leaf, varying like a parabola line, was higher in both the oldest leaf (the first leaf in low position) and young leaf (the fifth leaf in high position), and was the lowest in the third leaf (leaf in middle position) because of UV B radiation. Decrease in leaf extension rate, leaf number and area per leaf together resulted in the reduce of total leaf area. Variation of leaf growth played an important role in the relatively stable correlative growth among root, stem and leaf under the condition of enhanced UV B radiation. The decrease in the internode length lead to the reduce of plant height. The inhabited degree of net photosynthetic rate and apparent quantum efficiency by UV B radiation were positively correlative to leaf position. The photorespiration was significantly enhanced by UV B radiation and the increment was not obviously in relation to leaf position. UV B radiation had no effect on the dark respiration of the first leaf, slightly decreased the respiration of the second and third leaf, but sharply raised the dark respiration of the fourth leaf. It was suggested that the reduce of both plant height and leaf area was advantageous for plant to adapt to UV B radiation, decrease in the water content and photosynthesis and increase in photorespiration and dark respiration may be the physiological bases of growth inhibition. Fig 2, Tab 2, Ref 18