Water availability is one of the most important limiting factors in agriculture worldwide, particularly in arid and semiarid regions. Six spring wheat genotypes, i.e. three UK cultivars Cadenza, Paragon, and Xi-19 and three synthetic-derived lines L-22, L-24, and L-38, were grown in a phytotron under well-watered (until 40 days after sowing) and drought conditions. The aim of the study was to evaluate the traits related to photosynthetic capacity (net photosynthesis rate, stomatal conductance, internal CO2 concentration, transpiration rate, carboxylation capacity, instantaneous and intrinsic water-use efficiency) and plant biomass production in the cultivars and synthetic derivatives of wheat genotypes under well-watered and water-limited conditions. Genotypic variations in gas-exchange traits including net photosynthetic rate, carboxylation capacity, instantaneous water-use efficiency, and biomass yield were found amongst genotypes. Drought significantly reduced the total dry matter per plant. The synthetic derivatives L-22 and L-24 showed higher performance of stomata for most of the stomatal aperture characteristics. Total dry matter was positively related to net photosynthetic rate and to instantaneous and intrinsic water-use efficiencies. Finally, net photosynthetic rate was also positively related to stomatal conductance and transpiration rate under both the well-watered and water-limited drought conditions., S. Sikder, J. Foulkes, H. West, J. De Silva, O. Gaju, A. Greenland, P. Howell., and Obsahuje bibliografii
Closely related species can be used for studying the ecological significance of their traits. The response in terms of survival, clonal growth and vegetative and generative characteristics of three related Myosotis species to competition and soil characteristics were studied in a three year pot experiment. Plants from four populations per species were cultivated in a factorial combination of substrate (nutrient-rich soil and mixtures with sand) and competition (with or without Holcus lanatus) treatments. Survival, clonal growth and the majority of the growth characteristics of all three Myosotis species were reduced by competition. The effect of substrate was less pronounced, and variable for various traits: the soil with sand mixture was more suitable for survival, clonal growth and seed germination whereas in the nutrient-rich soil plants were taller, but this effect was modified by competition. The differences among species corresponded well to expectation based on their known habitat preferences. Myosotis caespitosa, a species typical of short-term habitats such as emerged bottoms of ponds, exhibited the shortest life span and was also the most sensitive to competition: all plants of this species died in the competition treatment before the end of the second season. Nevertheless, the surviving plants (in the no-competition treatment) were able to form several daughter rosettes or stolons; some of them spread clonally till the third year. Myosotis palustris subsp. laxiflora, which inhabits the banks of rivers and brooks often disturbed by torrential floods, survived best and had the highest potential for clonal growth and spreading. Most plants of this species produced rhizomes and stolons and spread the furthest of all the three species. Myosotis nemorosa, which lives mostly in meadows, the most stable habitat of the studied congeners, but also a habitat with a strongly competitive matrix of species, was intermediate in terms of survival, and clonal growth, forming mainly short rhizomes. This species exhibited the highest among-population variability in all recorded characteristics, which might be due to its local adaptation to a wide spectrum of habitats. We argue that the details of prevailing disturbance regime, rather than some general disturbance intensity explain the clonal behaviour of the species compared.