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No.50 (2003/12) >

 
Title :マングローブ3樹種の葉のガス交換特性に与えるNaCl濃度および環境要因の影響
Title alternative :Effect of NaCl concentration and environmental factors on the gas exchange characteristics of three mangrove species.
Authors :川満, 芳信
吉原, 徹
川元, 知行
徳丸, 慶太郎
Authors alternative :Kawamitsu, Yoshinobu
Yoshihara, Toru
Kawamoto, Tomoyuki
Tokumaru, Keitarou
Issue Date :1-Dec-2003
Abstract :慶佐次川流域において塩濃度勾配に沿って分布するオヒルギ,メヒルギ,ヤエヤマヒルギについて,葉身のガス交換,水ポテンシャル,イオン,窒素吸収特性を調査した.次に,塩処理をしたポット苗を用いて,光量子密度,葉温,外気のCO_2濃度を厳密に制御し,光合成特性を明らかにした.結果の要約は以下のとおりである.(1)慶佐次川流域に分布する4種のマングローブは,自然条件下において能力最大の光合成を行っていることが確認された.塩濃度が高い下流域に分布するヤエヤマヒルギは葉身の水ポテンシャルが低く,水利用効率は高かった.(2)塩濃度が高い場所に生育するマングローブ樹種は,葉身の全窒素含量が高く耐塩性との関係が示唆された.オヒルギは,K^+/Na^+比が低く特異的な浸透圧調節をしていることが示唆された.(3)根圏への塩処理は,光合成速度よりも気孔伝導度に大きく影響を及ぼした.種間で比較するとメヒルギが最も大きく減少した.(4)オヒルギ,メヒルギの植物体全体を400mM NaCl水溶液に沈めても,処理に関係なく光合成速度に影響を及ぼさなかった.
The mangrove can be classified by the photosynthesis mode asC_3 photosynthesis plant. However, it is also possible to classify the mangrove plant asspecial plant typeorsea weed, since it can grow in such high salinity conditions, whereas C_3 plants could not survive due to the low osmotic potential (-2.4MPa). The photosynthetic rate in the mangrove does not decrease even in -3.0MPa of leaf water potential, which is lower than the sea water. The photosynthetic rate of the normal C_3 plant starts decreasing when leaf water potential decreases from -0.6MPa, and it becomes almost zero at -1.5MPa. Therefore, the mangrove protects the photosynthetic apparatus from destruction with its special function, even when water potential decreases remarkably. The mangrove filters seawater at the root system, allowing only fresh water to move to the above-ground plant, consequently protecting the photosynthetic apparatus in the leaf. In addition, the photosynthesis is not affected even when seedling plants always experiences flooding and the lower leaf of Avicennia marina, which are submerged every day. In this paper, we measured light and CO_2 response curves of photosynthesis, stomatal conductance, and transpiration rate of the Okinawan mangrove species under different salinity conditions. In addition, to clarify the effects of submerged treatment into the see water on the gas exchange rate, we measured the gas exchange rate and leaf water potential before and after submerged treatment.
Type Local :紀要論文
ISSN :0370-4246
Publisher :琉球大学農学部
URI :http://hdl.handle.net/20.500.12000/3591
Citation :琉球大学農学部学術報告 = The Science Bulletin of the Faculty of Agriculture. University of the Ryukyus no.50 p.7 -19
Appears in Collections:No.50 (2003/12)

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