Studies On The Photosynthetic Performance And Dry Matter Production Of Supper High-yield Winter Wheat

In order to exploit the photosynthetic potentiality of super high-yield winterwheat, and then improve grain yield, a study was conducted in the fields of winterwheat with a grain yield about 9 t/ha for four varieties under limited irrigation. Thedynamics of net photosynthetic rate (P_n) of leaves, leaf area, leaf area duration anddry matter production were measured during winter wheat growing period. The mainresults were summarized as follows.1. The net photosynthetic rate (P_n)of all pre-winter leaves on the main stem ofwheat reached the maximum values when the leaves were fully expanded, thendecreased gradually with leaf senescence and the decrease of temperature. Forspring-growing leaves, the P_n of the second and the third leaves from top reached thehighest values at booting stage, and the P_n of flag leaf reached the maximum at 20days after anthesis. Comparison on the P_n among different leaves of all the fourvarieties tested after anthesis showed that, the P_n of flag leaf was the highest, thenthose of the second and third leaves from top, with those of the fourth and fitch leavesfrom top the lowest. And the differences of P_n among the different leaves obovebecame more significant during late growing period. These results showed that, themaximum values of P_n appeared later in super high-yield winter wheat, and that wasbenificial to dry matter production during grain filllig and the transportation ofassimilates to grains, then improve the average photosynthetic rate and totalphotosynthetic performance.2. Comparion of photosynthetic performance among different leaves in superhigh-yield winter wheat showed that, the highest photosynthetic rate decreased, andthe leaf area duration shortened with the leaf position from base to top before winter.The area of the third pre-winter leaf was the biggest, and the general photosyntheticperformance of the third leaf was also the best. During the growth period after winteruntil maturity, the general photosynthetic performance of the second leaf from top andflag leaf was the best. After anthesis, the top three leaves, especially flag leaf, hadhigher P_n and longer photosynthetic duration than other leaves.3. The changes of photosynthetic performance for individual plants of super high-yield winter wheat were that, the leaf area per plant increased gradually after"getting-up stage" (about double ridge stage of the spike differenciation), and reachedthe maximum values at booting stage, then decreased. The average photosyntheticrate for a plant was higher at getting-up and jointing stages, and kept the higher valuefor a longer period, then decreased. The leaf area per plant played a more importantrole in photosynthetic production per plant comparing with other components such asthe average P_n. The maximum values of leaf area for super high-yield wheat appearedlater, and then the maximum values of photosynthesis per plant were also later, whichwas beneficial to the dry matter production during late stage of grain yield formation.4. The maximum leaf area index (LAI) of super high-yield wheat was 7～8, andthe duration with higher LAI was longer and decreased slower. The LAI maintainedmore than 4.5 at 10 days after anthesis. Loaf area duration (LAD) was larger at eachstage, the total leaf area duration was more than 2.9×10~6 m~2·d/ha, and attained 8.8×10~5 m~2·d/ha after anthesis, provided the basis for assimilation after anthesis. Totalamount of dry matter accumulation of super high-yield wheat reached 19000 kg/ha,and the percentage of biomass after anthesis was high, especially the two varieties,Shixin 828 and Shimai 12, counted about 1/3. The harvest indices of the varietiesreached super high-yield (yielded≥9000 kg/ha) were 0.44～0.48. The results aboveshowed that, on the basis of enough total culms (main stems and tillers) per hectare,the basic practices of supper high-yield was to keep larger leaf area and prevent leavesfrom early-senescence after anthesis, improve the photosynthetic performance onplant and crop levels, increase population dry matter accumulation after anthesis, andimprove harvest index.