The effect of irrigation frequency on water and carbon relations in three cultivars of sweet pepper (Capsicum chinense Jacq), in a tropical semiarid region

The effect of three irrigation frequencies (3, 6 and 9 days) on water balance, gas exchange and fruit production of three cultivars of C. chinense was evaluated in the field with the aim of selecting the cultivars that are most resistant to water deficits, yet have high yields. A split-plot design with three replicates was employed. Available soil water content at the moment of irrigation was 68-80%, 35-45% and 8-20% of field capacity for 3, 6 and 9 days, respectively. Leaf gas exchange and leaf water potential were measured at 2 and 2.5 hour intervals, respectively, 45, 63, 87 and 101 days after transplanting from seed beds. Pressure-volume curves were used to determine osmotic potential at turgor loss. Fruit production was measured from weekly collections throughout the experiment. Early morning and minimum water potentials decreased at lower irrigation frequencies for two of the cultivars. A decrease in osmotic potential at turgor loss (0.25-0.42 MPa) was observed in the same two cultivars, indicating they are capable of adjusting osmotically. A significant reduction in maximum stomatal conductance was observed between plants watered every 3 (139-193 mmolm(-2) s(-1)) and 6 days (71-85 mmolm(-2) s(-1)). There were no differences between 6 and 9 days. The same trend was obtained for mean daily assimilation (4.7-5.6 mu molm(-2) s(-1) for 3 days and 3.0-3.7 mu molm(-2) s(-1) for 6 days). Fruit production was affected in different degrees depending on the cultivar (from 24% upto 40% reduction between 3 and 6 day frequencies). (C) 1999 Elsevier Science B.V. All rights reserved.