Influence of water stress on growth, yield and radiation use efficiency ofvarious wheat cultivars

Effects of water stress on growth, yield and radiation use efficiency (RUE) ofdifferent wheat cultivars were studied 1998-2000 at the Agronomic Research Area,University of Agriculture, Faisalabad. Four or five irrigation treatments, based,soil moisture deficit, were applied to each cultivar in the two seasons. Irrigationtreatments were designed to induce a range drought treatments from fullirrigation to no irrigation between emergence and harvest. Leaf area index,radiation intercepts and biomass accumulation were measured throughout thegrowing season. In both seasons there was a highly significant positiverelationship between cumulative intercepted PAR and biomass production. The RUEof wheat ranged from 1.99 to 2.71g DM MJ-1 intercepted PAR in both the seasons.Results showed that the highest yields were obtained from fully irrigatedtreatments; yield variations among treatments were caused by affecting both theamount of intercepted PAR and RUE Drought imposed throughout or afteremergence early in the season depressed RUE significantly by 29.7 to 32.8%(1998-1999) and 10.9-15.5% (1999-2000) compared with the fully irrigationtreatment. In treatments where drought was imposed later in the growth (beforeanthesis or later), the primary cause of reduced biomass production was adecrease in the RUE to a lesser extent in the amount of intercepted PAR, mostlyassociated with low photosynthesis rate. The response of cultivars to radiationinterception was slight and significant only during 1999-2000. Final grain orbiomass yield was sensitive drought timing, especially to maximum potential soilmoisture deficit for the early than the later drought treatments.