| Summary: | 碩士 === 國立臺灣大學 === 森林學研究所 === 88 === This study was aimed to the physiological and morphological responses of the following native broad-leaves tree species, Taiwan wingnut(Juglans cathayensis), Formosan michelia(Michlia compressa), devil tan oak (Lithocarpus lepidocarpus), ring-cupped oak (Cyclobalanopsis glauca), and chinese cork oak(Quercus variabilis) to the various light intensities. The seedlings were grown in full sunlight and artificial shading environment, relative light intensity 49% and 29%, respectively. The physiological and morphological attributes of them were observed after the new shoots were elongated in different light intensities.
During the maturing period of leaves, chlolophyll concertration of most species increased progressively. The only decrease occurred on October 28 in Taiwan wingnut in the full sunlight regime. The chlolophyll concentration in the mature leaves of all five species in shading conditions exceed those in the full sunlight regime. Due to the decrease in transpiration and rise in leaf temperature, net photosynthetic rate gradually decreased after 9:30 a.m. However, because of the maintenance of stomatal conductance and lowest leaf temperature, the net photosynthetic rate of devil tan oak gradually increased as light intensity increased from 9:30 a.m. to 1:00 p.m . In condition of 49% light regime, the net photosynthetic rate of all five species gradually increased as light intensity increased , and performed their highest rates at 10:30 a.m. Morever, in condition of 26% light regime, net photosynthetic rate rose in accordance with the light intensity, manifested a general tendency of progressive increase.
The specific leaf area in all five species were increased with the reduction of the light intensity of the growth environment. In shading environments, the stomatal densities of Formosan michelia, Taiwan wingnut, and devil tan oak clearly exceed those in full sunlight regime. The size of stomatal guard cells in Formosan michelia and Chinese cork oak varied significantly in different light regimes. In shading environments, the relative high/width ratios of palisade cells in Taiwan wingnut and Chinese cork oak were obviously lower than those in full sunlight regime. The lenghth of trichome of devil tan oak leaves was shortened with the reduction of light intensity.
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