葡萄叶片光合速率与量子效率日变化的研究及利用

STUDY OF DIURNAL CHANGES IN PHOTOSYNTHETIC RATE AND QUANTUM EFFICIENCY OF GRAPEVINE LEAVES AND THEIR UTILIZATION IN CANOPY MANAGEMENT

在土壤供水充足的自然条件下，葡萄（Ｖｉｔｉｓ ｖｉｎｉｆｅｒａ Ｌ．）光合量子效率在上午最高，尔后下降，出现“中午降低”现象。上午光能截留高的叶片的光合量子效率较高，中午减少叶片光能截留有利于缩小“中午降低”的幅度。一天中始终处于强光照射下的叶片的光合量子效率“中午降低”明显而持久，且在下午得不到恢复。光合速率与量子效率的日变化与叶肉对ＣＯ２ 阻力的变化密切相关，而与气孔下腔细胞间隙中ＣＯ２ 浓度变化关系不大。在人工气候室中土壤水分、空气湿度、叶温、ＣＯ２ 浓度等环境因素稳定而适宜的条件下，饱和光强以上的光（１２００μｍ ｏｌ·ｍ － ２·ｓ－ １）持续照射使葡萄叶片出现“光抑制”；用亚饱和光（８００ μｍ ｏｌ·ｍ － ２·ｓ－ １）和低光（２００ μｍ ｏｌ·ｍ － ２·ｓ－ １）持续照射一定时间后，也使叶片光合量子效率比照射开始时随照射时间的持续而不断降低，出现类似于“光抑制”的现象。稍高于补偿光强的弱光（１００ μｍ ｏｌ·ｍ － ２·ｓ－ １）持续照射下叶片光合量子效率稳定不变。讨论了“类似光抑制”现象。实验结果还认为葡萄叶片一天中叶肉阻力的变化与“光抑制”部分地相关联。分析调控葡萄光合速率与量子效率日变化的内外因素，指?

Photosynthetic rate and quatum efficiency of grapevine (Vitis vinifera L.cv.Sauvignon blanc) leaves were measured under the field with ample soil water supply, and in phytotron with ample supply of water and mineral nutrients, constant air humidity and CO 2 concentration, and optimum air temperature, respectively.Under field conditions CO 2 assimilation quantum efficiency of leaves reached its maximum in the morning, which was followed by continuous decrease and midday depression.The leaves intercepting more light energy in the morning showed a higher quantum efficiency.Those leaves subjected continuously to strong irradiance exhibited a more obvious and longer midday depression.Reduction of leaf light interception around midday could reduce midday depression.Shaded leaves had a higher quantum efficiency than leaves under direct sunlight.The diurnal changes in photosynthetic rate and quantum efficiency of leaves were shown to be closely related to the variations in mesophyll resistance to CO 2.In phytotron experiments the photosynthetic quantum efficiency of leaves was reduced after a certain period of illumination not only at 1200 μmol·m -2 ·s -1 PFD, higher than the saturating light of vine leaves (≈1000 μmol·m -2 ·s -1 ), which was caused by “photoinhibition”, but also at 800 and 200 μmol·m -2 ·s -1 , which was similar to “photoinhibition”.But photosynthetic quantum efficiency of leaves exposed continuously to a very weak PFD (100 μmol·m -2 ·s -1 ) remained contant.The diurnal changes in mesophyll resistance to CO 2 of vine leaves could be partly related to photoinhibition. It is considered that, under field conditions without soil water limitation, midday depression of vine leaf photosynthesis could be a result of an increase of the mesophyll resistance induced by multiple effects of strong light, high temperature and low humidity.A higher light interception by canopy plane in the morning may be advantageous to exploit higher photosynthetic potentiality of leaves, but a lower light interception in the middle of day may reduce midday depression.The north south orientation plane can provide optimum light regime and improve photosynthetic environment in vineyards.