The effect of freezing temperature on physiological traits in sunflower

This study was conducted to identify the physiological mechanisms associated with the resistance and tolerance of young sunflower plants to freezing temperatures. The effect of overnight temperature –3°C on the maximal quantum efficiency of PSII (Fv/Fm), the relative electrolyte leakage (REL) and the osmotic potential (Ψπ) was determined in five genotypes of sunflower: C33, C98, C124 and C148 were chosen from the population of recombinant inbred lines (RILs) based on contrasted responses to low temperature, and a wild genotype 2603 that was chosen for its ability to maintain activities in cold conditions. The night temperature –3°C over the course of 10 h caused an immediate significant decrease of Fv/Fm in C33, C98, C124 and C148. In the case of genotype C98, the effect of this freezing temperature was manifested by a significant increase of REL. Significant changes of Ψπ, as a reaction to the effect of freezing temperatures, were not found in any of the monitored genotypes. The measurements of the physiological traits after 5 days of regeneration indicated the renewal of integrity of cellular structures and an increase of PSII reaction centre efficiency in all monitored genotypes. From the point of view of tolerance or sensitivity, the wild genotype 2603 showed itself as tolerant towards the tested freezing temperature, displaying insignificant differences with control plants in all monitored traits. Genotype C98 appears to be the most sensitive from the monitored set, with evident changes in two traits signalling frost damage

The influence of drought on the utilisation of nitrogen ( ¹⁵ N) by two modern and one historical spring barley ( Hordeum vulgare L.) varieties

In an experiment with two modern varieties (Amulet and Krona) and one historical variety (Nűrnberg) of spring barley stress, invoked by drought, significantly reduced the % content of N and the total amount of accumulated N in the plant bodies in all varieties. On the contrary significantly increased the percentage of N from fertiliser ( 15 N) to the total nitrogen in the plants. Varietal differences were expressed as a tendency to greater accumulation of total N and N from fertiliser ( 15 N) in the modern varieties than in the variety Nűrnberg. On the contrary this variety was found that there was a greater proportion of 15 N to the total amount of N in the plants. Under normal moisture conditions the nitrogen from the fertiliser ( 15 N) was taken in and utilised by the spring barley primarily in the first half of vegetation period and, as a rule, its accumulation in the plants peaked during flowering. Drought slowed down its intake and usage and shifted the maximum accumulation to the post-stress i.e. post-floral period

The impacts of the aridisation of a habitat on the photosynthetic fixation of energy in spring barley ( Hordeum vulgare L.)

Aridisation of a habitat is expressed by a reduced photosynthetic fixation of energy in the plants especially in the photosynthetic organs — the leaves. The quantity of energy fixed by plants can be increased by additional intensification methods such as nitrogen fertilisation. However, this places very high demands on additional inputted energy and involves gradual exhaustion of non-renewable resources. These intensification methods also have a negative effect on the environment

The effect of the aridisation of a habitat on the accumulation capability of sink in selected varieties of spring barley

One of the ways of reducing energy-intensive inputs to agricultural systems is to replace the less performing cultivars with more productive ones and to cultivate varieties with sufficient accumulation capabilities of sink even under worse environmental conditions, for example, in the event of aridisation of the environment. The cultivation process is managed in such a way so that the largest share of the total production of all the plant biomass is represented by the organs providing the actual economic yield. From the results there is a clear difference between the Czech variety Malz and the Dutch Jersey in the formation of spike under the effect of water stress. For the Malz variety the number of grains in the spike dropped by 17.5% compensated for by their increased weight. For the Jersey variety there was a 16.7% fall in the number of grains in the spike, but no compensation in the increased weight of the grains was observed

The effect of abscisic acid on rate of photosynthesis and transpiration in six barley genotypes under water stress

For six barley genotypes evaluated from various climatic areas mild water stress resulted in reduced gas exchange parameters (P N a E). For all (except the Mexican Namoi) there was a fall in the water use efficiency (WUE). The largest fall was recorded for the French genotype Adagio. Treating the plants with abscisic acid under a mild water stress resulted in all genotypes showing further, statistically significant reductions in P N (except for the wild W 154) and E in comparison with untreated plants. ABA under mild water stress supported the plant’s water conservation and in a number of cases also improved the WUE (for the Czech genotype Maridol, the English Braemar, the French Adagio, the Israeli wild W 154 and partially in the Yugoslavian Novosadski)