Growth, chlorophyll content, photosynthesis and water relations in guava (Psidium guajava L.) under salinity and different nitrogen supply

The influence of NaCl and different levels of nitrogen supply (5, 10 and 15 mM Ca(NO3)(2)) on growth and physiological parameters of two Sudanese guav a cultivars (white and red fruit flesh) were investigated. Under saline con ditions shoot growth and leaf chlorophyll content In lava trees were reduce d. However, moderate N supply improved these parameters. NaCl salinity redu ced net photosynthesis rate (P-N) and transpiration (T) of both guava culti vars, but moderate nitrogen supply enhanced P-N and T. Stomatal resistance (R-s) was high under NaCl salinity conditions, whereas it was comparatively low for trees moderately supplied with nitrogen. The salinity-induced decr ease of P-N in red guava is attributed to stomatal closure. In white guava this was rather an effect of non-stomatal factors. The xylem flow rate followed similar patterns for both cultivars and for al l treatments except those supplied with NaCl only. The highest flow rates w ere noticed for both cultivars under moderate nitrogen supply. The red guava is supposed to possess a better salt tolerance compared to wh ite guava.