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No.46 (1999/12) >
|Title alternative ||:||Effects of Nitrogen Supply on Growth Characteristics and Leaf Photosynthesis in Sugarcane|
|Authors ||:||川満, 芳信|
|Authors alternative ||:||Kawamitsu, Yoshinobu|
Singh, Ram Kumar
Nelson, Buah J.
|Issue Date ||:||1-Dec-1999 |
|Abstract ||:||サトウキビはC_4型光合成経路を有し, 光合成からみた窒素利用効率は極めて高いと云われる。本研究では, サトウキビの成長と光合成速度に与える窒素処理の影響を調べた。処理は水耕液中に含まれる窒素源としての硝酸アンモニウム(NH_4NO_3)の濃度を6段階に分け, 与えた。葉の窒素含量は処理濃度に比例して増大した。ON区の葉の窒素含量は0.81%で, 2N区のそれは2.28%であった。また, 草丈, 葉数も窒素処理濃度が上昇するにつれ増大した。処理開始後104日目に比較したところ, ON区の草丈は2N区の約半分であった。光合成速度及び蒸散速度の最大値は2N区で見られ, 最小値はON区ではなく1/3N区で認められた。1N区の葉身を用いて葉の各部位の窒素含量を比較したところ, 葉身上部が基部に比較して高く, 中肋は葉鞘とほぼ同じであった。SPADとクロロフィル含量との間には, 極めて高い正の相関関係が認められた。しかし, 両者間の回帰式の傾きは葉位によって異なり, サトウキビの葉にSPADを用いる場合, 注意を要する。光-光合成曲線に対する窒素含量の影響を調べたところ, 低窒素区では飽和型に, 高窒素区では不飽和曲線となった。ON区の最大光合成速度は2N区のものに匹敵し, 窒素を与えていないにも関わらず高い値を示した。|
The objective of the present study is to demonstrate the effects of applied nitrogen concentration on the uptake pattern and composition in different parts and investigate the relationship between uptake and physiological activities. We measured leaf number, plant height, leaf nitrogen content, chlorophyll content, and gas exchange rates. Nitrogen concentrations of the six nitrogen levels (0,1/6,1/3,1/2,1 and 2N) were prepared as 0,1.5,3,4.5,9 and 18ml per liter of NH_4NO_3 in nutrient solution. The all parameters measured were increased with increasing levels of nitrogen concentration up to twice of the control. Highest values at 104 days after transplanting in the number of fully expanded leaves, the total leaf number, and plant height, which were observed in the plants grown with 2N solution, were 12,14.2,and 209cm, respectively. The nitrogen content, SPAD, photosynthesis, and transpiration rates were increased with successive increase in the nitrogen concentration of nutrient solution from 0 to 2 times of the control. The leaf nitrogen content, SPAD, photosynthesis and transpiration were highest in the plant grown with 2N solution and these were 2.28,39.25,29.78 and 3.04,respectively. Nitrogen content in the leaf sheath, mid rib, blade of younger fully expanded leaf of the plant grown with the solution of normal nitrogen concentration were analyzed. The results showed that leaf blade contain highest nitrogen followed by mid rib and sheath. Concentration of nitrogen was higher in top portion as compared with the base. Nitrogen content was highest in the 6th leaf (2.11%), followed by the 5th leaf (2.03%). It might be due to more actives of younger fully expanded leaf, besides these nitrogen concentrations. The 6th leaf from tip recorded maximum leaf nitrogen content, whereas the 5th leaf showed highest SPAD, photosynthesis and transpiration rates. Leaf nitrogen content showed a positive correlation with SPAD and photosynthesis indicating that nitrogen is the dominating factor on these parameter. In the present studies, 3rd leaf from tip, which is younger fully expanded leaf, indicated the higher photosynthetic nitrogen use efficiency, followed by 2nd and 4th leaf. The optimum temperature of photosynthesis was higher at the 2070 μ mol photons m^<-2> s^<-1> of PFD and lowering at 455 μmol photons m^<-2> s^<-1> of PFD. The optimum temperature of photosynthesis was not shifted with nitrogen levels as seen at different PFD. The maximum photosynthetic rate with 0N plants was higher than those of 1/6 and 1/3N plants. In addition, initial slope of the light dependent photosynthetic curves in 0N plants was also higher than those in 1/6N and 1/3N plants.
|Type Local ||:||紀要論文|
|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.46 p.1 -14|
|Appears in Collections||:||No.46 (1999/12)|
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