Effects Of Water Deficit On Photosynthetic Characteristics And Accumulation Of Assimilates Of Ears In Wheat

The shortage of water resources is one of the main factors, which restricts the high andstable yield of wheat.Studies in recent years have shown that the photosynthesis of ears has theobvious physiological advantage in wheat under water deficit. In high yield cultivation, it is theimportant theoretical and practical significance of crop production to give full play tophotosynthetic advantage of ear and mine photosynthetic capacity and assimilates productionpotential. In this study, Xinong1043, Shaan253, Pubing143, Zhenyin1were chose asexperimental material. Mid water stress (50%-55%of field capacity) and the control (70%-75%of field capacity) was given at the early jointing stage. Net photosynthetic rate, soluble sugarcontent and starch content was studied at at grain filling stage under water deficit.¹⁴C-isotopelabeling technique was used to investigate accumulation and transportation of¹⁴C-assimilates ofears at early filling stage under water deficit. Main results were listed as follow:1. The net photosynthetic rate of ears in Xinong1043under middle water deficit was raisedduring early filling stage, while in Shaan253fell into a reverse trend.¹⁴C-isotope labelingexperiments showed that the¹⁴C-assimilates of ears was largely transported to the seed underwater deficit in the mid-filling stage. Accumulation of¹⁴C-assimilates in the seed of Xinong1043and Pubing143under middle water deficit (74.11%,79.16%) was significantly higher than thecontrol (64.61%,74.86%), but¹⁴C-assimilates in the seed of Shaan253and Zhenyin1undermiddle water deficit (60.73%,70.54%) was significantly lower than the control (69.75%,75.42%). It indicated that middle water deficit can accelerate the transportation of¹⁴C-assimilates in ears of Xinong1043and Pubing143to the seed at early filling stage.2. Soluble sugar content of glumes in Xinong1043under middle water deficit was raised in25st DAA, while in Shaan253felling into a reverse trend. No significant difference was found intwo varieties after25st DAA. The content of starch in glumes and lemma of two varietiesdecreased first and then increased, and bottomed out at17st DAA. Compared with the normal,the content of starch in glumes and lemma of two varieties decreased, but decline of starchcontent in Xinong1043was significantly lower than that of Shaan253at5st DAA. Comparedwith the normal, the content of starch in glumes and lemma of Shan253decreased from5st to 17st DAA (P<0.01), while in Xinong1043fell into a reverse trend. It is interesting to note thatthe content of starch in glumes of Xinong1043bottomed out at17st DAA under middle waterdeficit, but that bottomed out at21st DAA under the normal. It indicated that water deficit couldaccelerate the degradation of starch in Xinong1043.3Distribution rates of palea/lemma, glumes and rachis in Zhenyin1and Shan253was raised atharvesting stages under water deficit, but distribution rates of palea/lemma and glumes in Xinong1043and Pubing143declined very slightly under water deficit. At harvesting stages, Distribution rates of¹⁴C-assimilate in palea/lemma and glumes in dry-land wheat under water deficit was a little higherthan the control, while in water sensitive wheat felling into a reverse trend. It indicated thatretention of assimilate in palea/lemma and glumes of water sensitive wheat raised under water deficit.But the retention of assimilate was not from the photosynthate of ear at early filling stage.4The drop of spikelet numbers, kernel weight per ear, aboveground biomass, grain yield,harvest index in Xinong1043and Pubing143was smaller than these in Zhenyin1and Shan253,but the thousand kernel weight of Xinong1043and Pubing143rinsed. Water use efficiency of thedry land wheat did not significantly affected by water deficits, but that of water sensitive wheatdeclined significantly.