Physiological responses of tomato plants (Solanum lycopersicum) as affected by root hypoxia

In order to investigate the effects of root hypoxia (1-2 % oxygen) on physiology and on some fructification parameters of tomato plants (Solanum lycopersicum cv. H63-5), a range of physiological and agronomic measurements were performed on plants submitted to gradual root hypoxia at the second leaf stage. Stomatal conductance (g(s)), total chlorophyll content, leaf area (LA) and leaf mass per area (LMA) were quantified at 14 days of treatment in the first leaf appeared before (L1) and after (L3) root hypoxia application. The results obtained showed that 7 days of treatment has slight effects on plant weight growth. However, 14 days of treatment caused decreased root dry weight (DW) with a concomitant increase in shoot DW. Root hypoxia significantly decreased g(s) and chlorophyll content of L3, but no effects were noted for L1. LA was significantly reduced for L1 and L3, contrary to LMA which was significantly increased. At the reproductive stage, root hypoxia resulted in a decrease in flower and fruit production, accelerated the entrance in the fruit expansion phase, but did not affect the rate of fruit growth, nor the final fruit size.