PHOTOSYNTHATE DISTRIBUTION IN WHEAT VARIETIES DIFFERING IN PHOSPHORUS EFFICIENCY

Abstract

The distribution of phosphorus (P), photosynthates, and the amount of assimilated 14C secreted as root exudate were measured in wheat genotypes differing in phosphorus efficiency. Two wheat genotypes, one P-efficient (Triticum aestivum L., cv. Xiaoyan 54) and the other inefficient (Triticum aestivum L., cv. Jing 411) were used in this study. The plants were cultivated in solution culture for 4 weeks under controlled conditions. Xiaoyan 54 had higher relative yield, higher P concentration in roots and higher root/shoot ratio than Jing 411 under P-deficient condition. Xiaoyan 54 distributed more P and assimilated carbon to the roots than Jing 411 under P deficiency and also released a higher percentage of assimilated 14C as root exudates. The percentage released was 3.98% for Xiaoyan 54 and 2.47% for Jing 411 under P deficiency, and 2.95% and 3.28%, respectively, under P-sufficiency. However, P deficiency led to more assimilated 14C being partitioned to roots by both wheat genotypes. Regardless of genotypes, the 14C distributed to roots of P-deficient plants was 5 to 6 times that of P-sufficient plants. The P-efficient genotype translocated more assimilated 14C to roots than the P-inefficient genotype under P deficiency and the difference between the two genotypes were smaller under P sufficiency. It is concluded that Xiaoyan 54 has higher relative biomass and better root system under P limited condition, which main reasons are that Xiaoyan 54 can maintain a higher P concentration, release more root exudate, and distribute P to roots.