GAS EXCHANGE OF PEPPER GROWN IN LYSIMETER UNDER DIFFERENT IRRIGATION REGIMES

In 1988, a research project was carried out in the Experimental Field Station of the CNR Irrigation Institute in Ponticelli-Naples with the aim of evaluating the physiological response of pepper plants grown in lysimeter under three irrigation regimes: a well watered treatment (WWT) was thoroughly irrigated, a stressed treatment (ST) only twice when wilting was evident, and a treatment with plants recovered from water stress (RT), irrigated as WWT after an initial drought period.

Twelve daily cycles of gas exchange measurements were made from the 34th to the 123th day after transplanting by a closed system, along with measurements of pre-dawn and hourly leaf water potential.

WWT initially had higher canopy photosynthesis, which supported early fruit growth and led to the highest yield, compared to RT. Viceversa, the late developed fruits of RT did not have time to size, so as yield was slightly less than WWT one, despite the active gas exchange rates. These were presumably linked to a stimulation of new leaf growth after the ricovery, which increased the percentage of leaves near peak photosynthesis. New fruit development late in the season may also have had a stimulating sink feedback effect on photosynthesis.

The dry treatment gave the lowest net canopy photosynthesis (NCP) and yield, linked to an afternoon NCP decline, more evident than in irrigated plots; NCP peaks were reached earlier in the day in the stressed treatment. When watered, stressed plants recovered and leaf water potentials and gas exchange rates appeared close to the corresponding values of WWT. Even though ST underwent a severe water stress (pre-dawn leaf water potential about - 1.7 MPa), it recovered by raising canopy photosynthesis to the level of WWT.