DETRIMENTAL EFFECTS OF FLUCTUATING HIGH CO2 CONCENTRATIONS ON PEPPERS

Plants of pepper (Capsicum annuum L.) were grown in controlled environ ment chambers at ambient (360 mu mol mol(-1)) and fluctuating pulse-en riched CO2 concentrations (700 mu mol mol(-1) daily average, ranging f rom 500 to 3500 mu mol mol(-1) = ECO(2)) under two water regimes. A de crease in plant growth and yield together with frequent visual injurie s was found in plants growing under ECO(2). Root/shoot ratio was great er, chlorophyll concentration and respiration rates were lower, and st omatal conductance and relative importance of alternative pathway resp iration were higher under ECO(2). The negative effects of ECO(2) were more intense under high water availability. The symptoms produced by E CO(2) were similar to those of resource limitation, and were alleviate d with increased nutrient supply. Constant elevated CO2 concentrations (700 mu mol mol(-1)) increased pepper production and did not produce any of the injuries described for this erratic ECO(2) treatment. Thus, it is probably the erratic nature of the CO2 concentration and not th e gas itself that was causing the injury.