Productivity Differences Among Different Winter Wheat Tiller Positions And Their Physiological And Biochemical Basis

In this study, we used two winter wheat cultivars: Shannong15and Shannong8355, andapplied the field experimental plots, to study the productivity differences among differentwheat tiller positions and their physiological and biochemical basis. Simultaneously, we alsoused the wheat cultivars: Ji’nan17and Shannong8355, and applied an outdoor potexperiment, to study evaluation of freezing resistance of different tiller positions during stemelongation stage based on the responses of the physiological indices to low temperature stress.The experiments were conducted at Experiment Station of Shandong Agricultural University.The main results are as follows:1The analysis of productivity differences among different wheat tiller positions1.1The differences of yield and yield components among different wheat tiller positionsWith the tiller position rising, the grain number per spike, fertile spikelet number perspike, single-kernel weight and yield per spike of the two wheat cultivars all declined, apartfrom the sterile spikelet number per spike. The study showed that the lower tiller position, themore grain number per spike, fertile spikelet number per spike and single-kernel weight, butthe less sterile spikelet number per spike. Consequently, the earlier tillers had higher yield perspike than that of the later tillers.1.2The differences of flag leaves photosynthetic characteristics among different wheat tillerpositionsDuring grain filling stage, the flag leaves photosynthetic rate presented descending trend,and the earlier tillers had higher flag leaves photosynthetic rate than that of the later tillers. The change trend of the photosynthetic rate had a little difference between two wheatcultivars. The result of correlative analysis showed that a high positive correlation betweenyield per spike and the flag leaves photosynthetic rate. That was to say the higher flag leavesphotosynthetic rate during grain filling stage might be one of the reasons why the earliertillers had higher yield per spike.1.3The differences of functional leaves senescence characteristics among different wheattiller positionsDuring grain filling stage, SOD activities of the functional leaves decreased gradually,activities of POD and CAT presented type “∧”, and the contents of MDA increasedgradually. Compared with the same leaf layer of the different tiller positions, the functionalleaves of earlier tillers had higher antioxidant enzyme activities, more soluble proteinscontents, but less MDA contents than those of later tillers. The results of correlative analysisshowed that yield per spike had remarkable positive correlations with antioxidant enzymeactivities and soluble proteins contents(apart from5DPA, SN15), but had remarkablenegative correlation with MDA contents.1.4The differences of grain filling characteristics among different wheat tiller positionsThe process of grain weight growth in both of the two wheat cultivars presented type“S”, and the process of grain filling rate presented type “∧”. The earlier tillers had highergrain filling rate and grain weight growth rate than those of later tillers. The results ofcorrelative analysis showed that grain weight had remarkable positive correlations withGRmaxand GR, had negative correlation with tmax,GR, but not with D. That was to say thatgrain weight was mainly dependent on grain filling rate but not on duration.During grain filling stage, the change trend of ZT, IAA, ABA contents respectivelypresented type “∧”, type “∧” and type “V”. And GA contents gradually decreased orpresented type “V” trend. The contents of grain endogenous hormones in earlier tillers weregenerally more than those in later tillers, apart from ABA during late filling stage. The resultsof correlative analysis showed that grain filling rate not only had remarkable positivecorrelations with ZT, IAA and ABA contents during early filling stage, but also had positive correlations with GA and IAA contents during middle filling stage. That was to say thatendogenous hormones had some regulating effects on grain filling process. More endogenoushormones in grain could also promote the grain filling rate.2Evaluation of freezing resistance of different tiller positions during stem elongation stagebased on the responses of the physiological indices to low temperature stressWith two winter wheat cultivars, Ji’nan17and Shannong8355, the experiment wasconducted. The activities of SOD, POD, CAT and the contents of MDA and soluble protein ofwinter wheat tillers were measured as the physiological indices to evaluate the freezingresistance. The comprehensive evaluation of freezing resistance coefficient of activities ofSOD, POD, CAT as well as contents of MDA and soluble protein of the tillers wereconducted with the principal component analysis and cluster analysis. The results showed thatthe activities of SOD, POD, CAT increased, and the contents of MDA and soluble protein notonly increased but also decreased both in functional leaves and sheath of each tiller duringstem elongation stage under low temperature stress. The cluster analysis was used to dividethe tillers of each cultivar into three kinds of freezing resistance type. For Ji’nan17, the mainstem, tiller Ⅰ and tiller Ⅱ belonged to high freezing resistance type; tillerⅢ, tiller Ⅳandtiller Ⅰ-p belonged to medium freezing resistance type; the rest tiller Ⅱ-p belonged to lowfreezing resistance type. For Shannong8355, the main stem, tiller Ⅰ, tiller Ⅱ and tillerⅢbelonged to high freezing resistance type; tiller Ⅳ and tiller Ⅰ-p belonged to mediumfreezing resistance type; the rest tiller Ⅱ-p belonged to low freezing resistance type. Resultsof this study indicated that the cold tolerance ability of the main stem and the earlier tillerswas higher than that of the later tillers.