Utrillas, M. J., Alegre, L. and Simon, P. (1995): Seasonal changes in production and nutrient content of Cynodon dactylon (L.) Pers. subjected to waterdeficits. —
Plant and Soil 175
We aimed to study the influence of soil water deficit on gas exchange parameters, dry matter partitioning in leaves, stem and spike and grain yield of durum (Triticum durum Desf.) and bread (Triticum aestivum L.) wheat genotypes in the 2013–2014 and 2014–2015 growing seasons. Water stress caused reduction of stomatal conductance, photosynthesis rate, transpiration rate, an increase of intercellular CO2 concentration. Photosynthesis rate positively correlated with growth rate of genotypes. Drought stress caused adaptive changes in dry matter partitioning between leaves, stem and spike of wheat genotypes. Stem dry mass increased until kernel ripening. Drought stress accelerated dry mass reduction in leaves and stem. High growth rate of spike dry mass was revealed in genotypes with late heading time. Spike dry mass positively correlated with photosynthesis rate and grain yield. Generally, bread wheat is more productive and tolerant to drought stress than durum wheat.
This study aimed to analyze drought tolerance in bread wheat by examining the effect of soil water deficit on yield performance of synthetic bread wheat derivatives. Thirteen genotypes of synthetic bread wheat derivatives selected from a backcross (Cham 6 ///Haurani /
ICAG400709 //Cham 6) were used for field evaluation in two experimental sites for two consecutive years. In addition, three synthetic wheat genotypes grown under different planting dates were compared for yield performance. Grain yield was highly correlated with harvest index under all of four cropping environments. No significant contribution of biomass to the grain yield was found in these plant materials. Late planting generated plant growth under the drier soil conditions after the heading time than under normal planting conditions, which resulted in considerable grain yield reduction. A synthetic wheat genotype selected from the materials showed significantly higher grain yield under late planting condition than the check variety, Cham 6. These results suggest that higher grain yield in a synthetic bread wheat genotype is associated with rapid translocation of photosynthetic carbohydrates to the grains after heading time.
This experiment was carried out to evaluate the canopy temperatures and excised leaf water loss (ELWL) of tef cultivars under water deficit conditions at anthesis and to demonstrate that these indices are reliable indicators of plant water stress. Twelve tef cultivars of similar maturity group but diverse origin were grown in each of two seasons under stressed and non-stressed conditions at anthesis. Mean cultivar canopy temperatures ranged from 33.2 to 34.9°C and 32.2 to 33.8°C in 1998 and 1999, respectively. There was also a significant difference in canopy temperature between treatments. The canopy temperature of stressed plants was 10.7% and 11.4% higher than that of non-stressed plants in 1998 and 1999, respectively. Under stress conditions the canopy temperature of the cultivars ranged from 33.6 to 36.7°C and from 33.1 to 37.6°C in 1998 and 1999, respectively, as compared to the non-stressed plants which ranged from 32.1 to 34.5°C in 1998 and from 29.7 to 31.9°C in 1999. There was a marked difference in mean excised leaf water loss (ELWL) values between the stressed and non-stressed treatments. There was also a differential response among tef cultivars for ELWL in response to the water deficit treatments during 1998 and 1999. Under non-stressed conditions the values of ELWL ranged between 1.5 g/g/h to 2.1 g/g/h in 1998 and 0.8 g/g/h to 1.7 g/g/h in 1999, whereas under stressed conditions the ELWL of the cultivars ranged from 1.0 g/g/h to 1.8 g/g/h and 0.7 g/g/h to 1.3 g/g/h in 1998 and 1999, respectively. The difference between the cultivars for both canopy temperatures and ELWL in response to the water deficit treatment was greater during 1999 than in 1998. It was concluded that both canopy temperatures and ELWL were suitable methods for the screening of drought resistant tef cultivars since differences between cultivars were detected.
Soil water balance was studied in a 25-year-old experiment, on chernozem soil, in different crop-rotation systems (mono-, bi- and triculture) in dry (2007) and rainy (2008) seasons, in maize production. Soil water deficit values in maize production were much lower in 2008 than in 2007 in non-irrigated and irrigated plots of three crop rotation systems because of favourable precipitation supply. We found difference between the water deficit values of two irrigation treatments. We measured lower values in irrigated plots of three crop-rotation systems before sowing: non-irrigated plots in monoculture 105 mm, in biculture 101 mm, in triculture 121 mm and irrigated plots in monoculture 90 mm, in biculture 91 mm, in triculture 111 mm. Soil waterstock started to decrease with the rise in average temperature and, despite an increase in precipitation quantity, we calculated higher water deficit values. Precipitation in August and the high average temperature intensified the water deficit. Water deficit showed its highest values in early September. We examined the water balance of the soil profile in 0–2.0 m and we concluded that the water deficit of the 0.8–1.2 m soil layers was most intensive in both non-irrigated and irrigated treatments, because of significant root mass. Our results showed that irrigation had a more important influence on the yield in a dry cropyear (2007 characterized by abiotic, water stress) than in an optimum water supply cropyear (2008).