A Preliminary Note on the Photosyn Thetic Rate of I-Geo-Gen Leaf in Relation to the Red Discoloration under Low Temperature

Abstract

To test if the red discoloration of leaves usually observed in I-geo-gen is related to low temperature and also if the photosynthetic rate and the grain yield are adversely affected by the discoloration, a pot experiment was conducted. Rice varieties, I-geo-gen and Yükara, were grown in a greenhouse at 25-40°C. At about maximum tillering stage, two temperature treatments, i.e., 13-20°C and 25-40°C (normal) were differentiated. These pots were returned to the normal temperature after eleven-day treatments. The apparent photosynthetic rate was then measured on certain intact leaves to see the effect of temperature treatment. Significant red discoloration of leaves and also a decrease of apparent photosynthetic rate were observed in J-geo-gen after the low temperature treatment, whereas there was no such phenomenon in Yãkara. It is suggested that low temperature causes more decrease in the grain yield due to the discoloration of leaves which accompanies a decrease of photosynthetic rate of leaves in indicas than japonicas. 為探討矮腳尖水稻常見之葉片紅化現象，是否與低溫有關，及此種紅化是否對光合成速率和稻谷收量有不良影響，乃舉辦盆栽試驗。 試驗主要係在25~40℃之玻璃室內進行。供試品種為本省北部之矮腳尖和日本北海道之Yukara。前者屬印度型而後者則屬日本型。 當水稻大約達最高分蘗期時，各品種水稻之半數盆栽（二重覆）則被移置於 13~20℃玻璃室，而另半數盆栽則繼續放置於25~40℃玻璃室。被放置於低溫玻璃室之水稻經過11天後再恢復移置於25~40℃玻璃室，隨後則測定各盆水稻中若干特定位置之葉片光合成速率，以觀察溫度處理對光合成速率之影響。 矮腳尖經過低溫處理後其葉片有顯著紅化現象，其光合成速率亦顯著低落，而 Yükara卻無。矮腳尖經過低溫處理者其平均粒重亦較對照處理（即無經低溫處理者）顯著低減。 由本試驗結果推測矮腳尖或一般印度型品種葉片之紅化，可能和低溫有關，而此種葉片之紅化將隨伴光合成速率之低下而影響稻谷收量。