大叶黄杨叶片表皮组织的聚光效应及其对叶片内部光分布的影响

利用自制的光纤微探测器研究了大叶黄杨 (EuonymusjaponicusT .)叶片内部的光分布。叶片表皮组织具有聚光效应 ,用金相砂纸磨去叶片的上表皮组织可以去除这种效应。用 6 6 0nm的红光照射叶片时 (从上表皮方向 ) ,叶片内部光量迅速下降 ,在不到 10 0 μm的路径上光量下降到初始值的 2 0 %。叶片内部光分布微分曲线说明 :叶片表皮组织的存在有利于叶片内部各组织之间光吸收的均匀化。分析叶片内部红光分布曲线 (照射上表皮方向以及照射下表皮方向 ) ,海绵组织对红光 (6 6 0nm)吸收较少 ,这可能是海绵组织的一种生理生态意义上适应性的反映

THE LEN EFFECT OF THE EPIDERMIC CELL LAYER OF THE LEAF OF EUONYMUS JAPONICUS T. ON THE LIGHT GRADIENTS WITHIN LEAF

One underlying assumption of the photosynthetic model based on physiological and biochemical mechanisms is that different tissue layers within a leaf do not show much difference in light absorbance. However, this assumption does not consider the different optical parameters and photosynthetic capacity of different tissue layers within a leaf, resulting in a non-precise photosynthesis model. To measure the optical properties of different tissue layers, Vogelmann and Njorn(1984) made a microscopic fiber optic probe that was inserted into the leaf. The electronic circuit for the driving stepping motor of their probe is somewhat complex, and could be simplified. A home-made fabric microprobe was used to determine light distribution within the leaf of Euonymus japonicus T. The Len effect of epidermic cell layer was affirmed by our sand paper treatment. Light declines rapidly and exponentially within the leaf, the red light(660 nm) fell to 20% of initial value after passage through 100 μm from the adaxial(upper) surface of the leaf. Based on differential analysis of the light curve, it seems that the epidermic cell layer could facilitate the averaging light absorbance between different tissue layers within a leaf. Spongy tissue absorbed only a small proportion of red light(660 nm), for although about 20% of the red light transmitted leaf, it was not absorbed by the spongy tissue layer.``Our improvement of the microprobe produces good results, and can avoid the complex electronic circuitry of the driving stepping motor.