| Summary: | 碩士 === 國立中興大學 === 生命科學系 === 94 === In order to elucidate some physiological characteristics of hemiphyte in response to water deficit, Ficus microcarpa was used as material. It was treated with natural water deficit as well as artificial osmostic stress. Results showed that the change of leaf water potential (Ψ) was not so large, but stomata resistant (Rs) increased suddenly with the degree of stress level in both natural drought and artificial osmostic stress. Suggesting in water deficit F. microcarpa could avoid water loss by closing stoma. It was also found that predawn Fv/Fm of epiphytic F. microcarpa was closely related to the minimum temperature of measured day, the photosynthetically active radiation (PAR) of one day before measurement and Rs. For the Fv/Fm measured at noon, it was affected by average temperature of measured day, Rs, and Ψ. Besides, when leaves were treated with 1500 μmol m-2 s-1 PAR for 2 hrs, their Fv/Fm decreased with Rs increasing, in spite of under osmostic stress or not; but this decreasing was drastic for detached leaves. In addition, under high illumination, detached leaves showed lower qf (include qE and qT, two of NPQ relaxing within seconds to tens of minutes) than attached leaves, in spite of high NPQ in detached leaves; probably detached leaves could not protected their PSII by ABA from roots. Present study also used scotch tape to limit the diffusing of CO2 from atmosphere to leaves. The results indicated that stomata closing itself did not affect the efficiency of PSII. Therefore, the decreasing of PSII efficiency in osmotic stressed leaves was due to the other effects. In contrast to the F. microcarpa avoiding water loss by closing stoma, present study also found that Ψ of a phreatophyte-Salix warburgii decreased drastically under osmotic stress due to the insensitive stoma appearture.
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