Effects of drought on leaf area development, biomass production and nitrogen uptake of durum wheat grown in a Mediterranean environment

Abstract

A field experiment was carried out in Sardinia (Italy) on durum wheat to analyse the effects of different moisture treatments, irrigated (I), rainfed (R) and stressed (S), on leaf area index (LAI), radiation intercepted (Q) and water use (WU), efficiency of conversion of radiation and water into dry matter (RUE and WUE), nitrogen uptake and carbon and nitrogen partitioning in the above-ground part of the plant. In the period between beginning of stem elongation and heading, drought affected the maximum LA1 in the most stressed treatment (4.7 in S v. about 6.9 in R and I), but not Q and WU. RUE was also lowered by drought in this period (0.68 in S v. about 0.95 g MJ-1 in R and I) as a reduced biomass was recorded in S at heading (528gm-2 in S v. 777 g m-2 on average in R and I). In contrast with the previous period, the reduction in LA1 between heading and maximum ear weight (MEW) determined a significant reduction in Q and WU, WUE and RUE, resulting, ultimately, in notable differences in the total biomass produced until MEW (1203, 930 and 546 gm-2 in I, R and S respectively). The amount of stem reserves relocated to the grain decreased as the level of stress increased, going from 223gm-2 in I to 9gm-2 in S and was accumulated almost entirely (from 76% of the total in I to 100% in S), in the post-heading period. Nitrogen percentage was not affected by the treatments applied apart from the higher values in stem and flag leaf in S later in the growing season due to an inhibition of nitrogen translocation in S. The total nitrogen uptake was lower in S (12.3gm-2) than in I (16.6gm-2) only as a consequence of the different dry matter accumulation patterns. The importance of WUE in this type of Mediterranean environment is discussed, with particular concern to the key role of modulation of leaf area development through the growing season.