光度與溫度對四種紅樹林苗木光合作用之影響

Photosynthetic Responses of four Mangrove Seedlings to Light Intensities and Temperatures

紅樹林是指生長在熱帶及亞熱帶沿海潮間帶或河口泥濘地之植物，主要是由紅樹科及一些適應此種環境的植物所組成，為存在於水域與陸地兩種截然不同環境間的特殊植群。為了瞭解紅樹林植物之光合作用對光度、溫度的反應，本研究以水筆仔（Kandelia candel）、五梨跤（Rhizophora stylosa）、海茄苳（Avicennia marina）及欖李（Lumnitzera racemosa）等四種苗木為材料，以11%、21%、40%、63%及100%五種相對光度處理之，測定其光合作用對光度之反應曲線、光合作用對溫度之反應曲線、氣孔導度、葉片角度等，及葉綠素螢光（Fv／Fm值）。結果發現四種苗木對光線的適應範圍很大，但仍以在高光環境下生長者有較佳之競爭能力。海茄苳苗木可能有較強之耐陰性，而欖李苗木在低溫下之耐陰性低，氣孔可能為影響紅樹林光合作用之主要因子，而Fv／Fm值受低溫高光顯著影響，顯示低溫對紅樹林之生育影響甚大。 Mangrove, a vegetation community that grows in tropical and subtropical zones, iscommonly found in tide area of seashore or muddy land of river outlet. This special vegetation, consistingof mainly by Rhizophoraceae and some other plants, has adapted itself to and survived in two differentenvironments, namely, submerging in water and land. Seedlings of four typical mangrove plants, i.e.Kandelia candel, Rhizophora stylosa, Avicennia marina, Lumnitzera racemosa, were selected for thecurrent experiment to measure their photosynthetic responses to five relative light intensities, i.e. 11%,21%, 40%, 63%, and 100%, as well to different temperatures. Dependent variables measured included therate of photosynthesis, stomatal conductance, chlorophyll fluorescence (Fv/Fm) and leave angle. Theresults showed that seedlings of all species tested had a considerably wide range of adaptability to lightintensity, with higher light intensity promoting better growth. A. marina showed the strongest, while L.racemosa exhibited the least shadow tolerance under low temperature. Stomatal conductance appeared to be one major factor influencing photosynthesis of mangrove species. Fv/Fm was influenced by lowtemperature and high light intensity. In general, the low temperature had a significant impact over thegrowth of mangrove.

Mangrove, a vegetation community that grows in tropical and subtropical zones, iscommonly found in tide area of seashore or muddy land of river outlet. This special vegetation, consistingof mainly by Rhizophoraceae and some other plants, has adapted itself to and survived in two differentenvironments, namely, submerging in water and land. Seedlings of four typical mangrove plants, i.e.Kandelia candel, Rhizophora stylosa, Avicennia marina, Lumnitzera racemosa, were selected for thecurrent experiment to measure their photosynthetic responses to five relative light intensities, i.e. 11%,21%, 40%, 63%, and 100%, as well to different temperatures. Dependent variables measured included therate of photosynthesis, stomatal conductance, chlorophyll fluorescence (Fv/Fm) and leave angle. Theresults showed that seedlings of all species tested had a considerably wide range of adaptability to lightintensity, with higher light intensity promoting better growth. A. marina showed the strongest, while L.racemosa exhibited the least shadow tolerance under low temperature. Stomatal conductance appeared to be one major factor influencing photosynthesis of mangrove species. Fv/Fm was influenced by lowtemperature and high light intensity. In general, the low temperature had a significant impact over thegrowth of mangrove.