Effects of Water Stress on Assimilation and Partitioning of ~(14)C of Different Leaves on the Main Stem of Cotton

An experiment was conducted under the shelter at Teaching Experiment Station of Hebei Agricultural University in 2007,with the help of 14C tracer technique,and used Bt-transgenic cultivar(cv.NuCOTN 33B) as the experimental material,during which three field moisture capacity degrees were set up: Severe drought(SD,35%～45% of field moisture capacity);Middle drought(MD,45%～65% of field moisture capacity);and normal water supply(CK,65%～85% of field moisture capacity).The results showed that the characteristics of 14C photosynthetic assimilation and partitioning varied with different water conditions and different parts and growth stages of cotton stem leaves.The synthesis of photosynthetic products of cotton leaves was inhibited under drought stress and 14C assimilation decreased.With the worsening of drought stress,the photosynthetic output of source leaves increased.The partitioning of source leaves photosynthate varied between different growth stages under different levels of water stress.Severe drought promoted the distribution of photosynthate to root and main stalk growing points at budding stage,but to neighboring bolls at flowering and bolling stage as well as boll-opening stage.Middle drought stress promoted the partitioning of photosynthate to root and main stalk growing points at budding and early flowering stages,to the lower organs at full flowering stage and mainly to the neighboring bolls at boll-opening stage.In a word,absorption and assimilation of 14C in leaves were inhibited and leaves photosynthesis were affected under water stress,accordingly the partitioning pattern in every organ of leaf photosynthetic products changed.