| Summary: | 碩士 === 國立中興大學 === 森林學系 === 90 === Mangrove is a vegetation community grows in tropical and subtropical zones and commonly found in tide area of seashore or muddy land of river outlet. They are special vegetation composed of mainly by Rhizophoraceae and some other plants that have adapted itself and survived in two different environments, namely, submerging in water and on land. In order to study photosynthesis of the mangrove vegetation, or specifically, about the physiological responses to light intensity and temperature, four typical mangrove seedlings such as Kandelia candel, Rhizophora stylosa, Avicennia marina, Lumnitzera racemosa were selected for the experimentation. Five relative light intensities, 11﹪, 21﹪, 40﹪, 63﹪, and 100﹪were used as treatments to detect response curves to light intensity as well to temperature. The dependent variables measured were amount of photosynthesis, stomatal conductance, and leave angle. In addition, in two different months chlorophyll content, soluble protein content, as well as Fv/Fm were measured.
The results showed that seedlings of all species tested had a quite wide range of adaptability to light intensity. However, the higher light intensity promoted the better growth. A. marina had showed the strongest shadow tolerance among four species, while L. racemosa exhibited the least shadow tolerance under the low temperature. Stomatal conductance may be one of the major factors influencing photosynthesis of mangrove species. The low temperature in winter had impacted on the chlorophyll contents of K. candel, R. stylosa, and L. racemosa, and it also impacted on the soluble protein content of R. stylosa, and A. marina. Fv/Fm also influenced by low temperature and high light intensity. In general the low temperature had a greater impact over the growth of mangrove.
In summary, the results indicated that K. candel had better competition ability in the district closer to the temperate zone; A. marina had the strongest adaptability to environment so that its distribution ranged widely; while R. stylosa, and L. racemosa were comfortable with tropical zone. These findings agreed with the actual geographical distribution of the species. Furthermore it was found that these mangrove species might had a large stomatal conductance under low saline water circumstance that accelerated water losses. Therefore, it became a barrier for the species to migrate into land area. From observed physiological characteristics of the mangrove species it is recommended that reforestation of R. stylosa, and L. racemosa shall be conducted in the area south of Chia-yi to increase the chances of success.
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