Relationship of Plant Growth and Chlorophyll Content in Field-grown Rice

Abstract

Changes of chlorophylls and fresh weight in leaf blade and whole plant of 5 rice genotypes were measured at the experimental farm of Taiwan Agricultural Research Institute during the first (1st) and the second (2nd) cropping seasons of 1998. The objectives were to study the correlation between chlorophyll content and plant growth and its seasonal variation. The ratio of chlorophyll a to chlorophyll b was also determined to clarify the role of pigmentation relationship during rice growth. It was shown that rice plants began with lower chlorophyll content, increased as plant develops, and decreased when plant aged. Pattern for seasonal chlorophyll variation is best fitted by the Gaussian function, with the determining factors (R) greater than 0.89. The total chlorophyll was higher in the 2nd crop than in the 1st crop and level of chlorophyll content was higher in the whole plant than in leaf blade. After excluding the influence of growth rate between crops, Gaussian function is also fitted to seasonal changes in total chlorophyll on the unit time baseline. Seasonal changes of fresh weight in leaf blade and whole plant followed a similar best fit curve pattern to the total chlorophyll. Plants grown in the 2nd crop had higher fresh weight values than those grown in the 1 crop at the relative transplanting days and unit time baseline. By regression analyses, it revealed a closed positive correlation (R^O.82) between fresh weight and total chlorophyll. The linear relationship shows that the amount of total chlorophyll had a pronounced effect on values of fresh weight in both cropping seasons. However, at the same chlorophyll content, rice plants grown in the 1 1 crop supported a higher fresh weight than those grown in the 2nd crop. By further analyze leaf and whole plant pigmentation (chlorophyll a and chlorophyll b) during plant growth, it was found that the ratio of chlorophyll a/b was a linear function, decreasing after transplanting. Plants grown in the 1st crop had higher values in green-to- yellow pigment ratio than those grown in the 2nd crop. 本文硏究旨在追蹤田間水稻葉片及全株葉綠素含量與鮮重之季節變化，據以評估 葉綠素與植株生長之關啐，並由葉率素a與葉綠素b比例之季節變化澄清色素比例所扮 演的角色。田間試驗係於行政院農業委員會農業試驗所農場進行，包括1998年一期作及二期稻作。試驗結果顯示，無論葉片或全株，葉綠素總量自生長初期開始增加至抽穗前達頂點再隨著成熟老化遞減。葉綠素總量在一、二期作的季節變化適Gaussian涵數，決定係數(R2)超過0.89。葉綠素總量在二期作全期皆高於一期作者，且全株葉綠素總量大於葉片葉綠素總量。經利用單位時間標準化轉換消除生長速率差異後，葉綠素總量季節變化仍適用於Gaussian函數，且在單位時間亦呈現類似於葉綠素總量之Gaussian函數曲線，且同時期二期作稻株鮮重也大於一期作稻株鮮重。經過回歸分所後發現，無論葉片或全株，鮮重與葉綠素總量之間呈現直線相關(R2>0.82)，顯見廿枼綠素總量在兩期作均顯著影響鮮重的表現。惟在相同的葉綠素總量下，一期作稻株具有較高的植體鮮重。又葉綠素ａ及葉綠素ｂ比例在一、二期作生育期間呈現直線遞減趨勢，然一期作稻株具有較高的葉綠素ａ／ｂ比值。