A High Internal Phosphorus Use Efficiency in Tea ( Camellia sinensis L.) Plants

摘要

This study was conducted to investigate the effect of extremely low level of P supply in the nutrient solution on growth, P uptake and utilization as well as gas exchange and chlorophyll fluorescence parameters in five different tea ( Camellia sinensis L.) seed stocks. Plants did not show any visual leaf symptoms during 90 days growth in the medium without P. The five tested seed stocks did not differ in response to low P. The optimum P supply was 50 ??M, plants grown at 100 ??M P showed significant growth inhibition up to 21-65% (pa?¤0.05). One of the main causes of growth inhibition was reduction of net photosynthesis rate firstly due to lower stomatal conductance and secondly as the consequence of inhibition of photochemistry of P deficient tea leaves. Phosphorus concentration of leaves and roots in severely deficient plants was 0.7-0.9 mg g-1 DW. Very low P concentration in combination with low growth inhibition demonstrated a high internal use efficiency in tea plants. Internal P use efficiency was increased up to 3.65 times in response to low P supply. Phosphorus deficiency did not cause higher surface area of roots, moreover, P deficient plants had a reduction of uptake rate up to 94%. Results suggested that, P deficient tea plants did not develop any strategy for higher P uptake from medium, neither in terms of changes in root architecture nor induction of high affinity P uptake systems. In contrast, an extremely high tolerance of tea plants to P deficiency is mainly due to high internal use efficiency.