Influence of phosphorus on gas exchange and plant growth of two morphologically distinct types of Capsicum annuum

Abstract

Tolerance to phosphorus stress was studied in Capsicum annuum L. Chile ancho cv. San Luis and bell pepper cv. Jupiter plants. Plants were fertilized weekly with Long-Ashton nutrient solution (LANS) modified to supply 0, 11, 22, 44, 66, or 88 g(P) m-3 (P0, P11, P22, P44, P66, P88). Phosphorus stress occurred in both cultivars at P0 and P11, with reduced plant growth and development. At P0, the lowest percentage of total biomass was directed toward reproductive growth. The root/shoot ratio was greatest at P0, reflecting greater dry matter partitioning to the root system. Growth of 'San Luis' was more sensitive to phosphorus stress than 'Jupiter'. A greater percentage of total biomass was directed towards reproductive growth in 'Jupiter' than 'San Luis'. Increasing P nutrition elevated leaf tissue P in both cultivars with highest leaf tissue P at P88. There were no differences in tissue P between P0 and P11 'San Luis' plants, whereas P0 'Jupiter' plants had the lowest tissue P. Low P-plants generally had the highest tissue N and lowest S, Mn, and B. In both cultivars, gas exchange was lowest at P0, as indicated by reduced stomatal Conductance (g(s)) and net photosynthetic rate (P(N)). Internal CO2 concentration and leaf-to-air vapor pressure difference (VPD) were generally highest with P-stressed plants. Phosphorus use efficiency, as indicated by P(N) per unit of leaf tissue P concentration (P(N)/P), was highest at P11. Generally, no P treatments exceeded the gas exchange levels obtained by P44 (full strength LANS) plants. Both P(N) and g(s) declined during reproductive growth in 'San Luis', which fruits more rapidly than 'Jupiter', whereas no reduction in gas exchange occurred with 'Jupiter'.