Study Of Leaf Area And Root Growth Of Winter Wheat Seedlings

Leaf is the most important organ for photosynthesis. And the value of leaf area indicates certain ability of photosynthesis. Supposed that assimilation is in direct proportion to leaf area, we try to find out the relationship between leaf area and root branching, thus we could known how assimilation determinate the characteristics of root branching in this paper. When express assimilation as biomass (dry matter), we also try to find out the distribution of assimilation in winter wheat root system, especially the distribution between main root axis and lateral roots, and segments away from root base.In the experiment, wheat (NongDa 189) plants were grown on a sand culture in a greenhouse. Relationship between leaf area and characteristic of root branching of winter wheat seedlings were studied, In addition, effects of phosphorus deficiency on leaf area, root morphology and measuring methods of root architecture were studied. Finally, based on Allometric models, we investigated the distribution of assimilation in winter wheat root system. Following are results obtained:After the first leaf differentiated, total leaf area increase exponential adapting to accumulated temperature (At). All the primary roots (most are 5 roots) have differentiated when the first leaf expended. The secondary roots and leaves on caulis differentiated synchronized subsequently. The total number of main root axis was linear with leaf area adapting to At. Growth of wheat root system is prominently contributed by leaves' photosynthesis. The first lateral roots and each of main axis are prominently correlated with leaf area. When building the primary root system, capability of getting assimilation and elongation pattern of each root are similitude. Thereinto, the total length of the first lateral roots is linear with leaf area.Root dry matter obtained by each primary roots are no different, yet differ in the secondly roots. There were more assimilation distributed to the primary roots then the secondly roots. In primary roots, assimilation increased slowly before At reach 4000 ℃·h, then rising quickly ranging between 4000℃ ·h and 7500 ℃·h, then slowing down again. In secondly roots, assimilation allocated to the fifth and the sixth root increase linearly, and assimilation allocated to the seventh and the eighth root increase drastically before At reach 8000 ℃·h, then slowing down. Under the conditions of phosphorus deficiency, the pattern of assimilation allocate are the seem as full nutrient except that assimilation allocated to radicle always lager than other primary roots. P deficiency restrained the growth of secondly roots which differentiated lately.The growth of winter wheat seedlings was not affected because of providing of nutrient by wheat seed. Stimulated by P deficiency, biomass of wheat increasing lightly (rise 21 and 34 percent compare to full nutrient when At reach 5085 ℃·h and 6051 ℃·h, respectively. Then leaf area reduced and biomass dropped down by consuming of the seed's nutrient. Both of the elongation rates and the length of apical unbranched zone of main root axis are decrease by P deficiency. No different of total root length between P deficiency and full nutrient because of short term experiment.