Influence of abiotic stresses on the content of net energy in winter wheat(Triticum aestivum L.) grains

Net energy content was studied in grains of representative cultivars of whe at: Astella, Olga, Plodna, Patria and Zdar. Grains were taken from plants c ultivated under controlled glasshouse conditions and under conditions with mutual combination of three representative abiotic stresses - low pH (pH), high temperature (T) and drought (S). There is a possibility to conclude ne gative impact of abiotic stresses on accumulation of rich in energy matters into wheat grains, as by the plants cultivated in stress conditions occurr ed the decrease of energy content in comparison with the control variant (F ig. 1). The grains from stressed conditions had 11.06% lower values of comb ustion heat. If we express this decrease in energetic equivalent, we get th e value 1.66 kJ.g(-1). Similar conclusions for plants stressed only by drou ght got Hansen, Diepenbrock (1994). Content of energy in 1 g of dry matter of wheat grains was, apart from the external factors, limited also by the g enotype of used cultivars, where in the amount of accumulated energy showed up the sensitivity or, alternatively, tolerance towards abiotic stresses. At the cultivar Astella (Fig. 1) of the control variant was the average com bustion heat value 15.97 kJ.g(-1), then at the stressed variant occurred th e decrease of net energy to 13.04 kJ.g(-1). By the cultivar Zdar (Fig. 1) w e have found at the control variant content of rich in energy matters 14.30 kJ.g(-1) and at stressed plants it was 13.86 kJ.g(-1), In view of gathered results it is possible to state, that for Astella cultivar we mentioned th e most considerable decrease of net energy between both studied variants of experiments, this decrease was 18.25% for the stressed variant and for the cultivar Zdar was noted the lowest decrease of combustion heat values (2.3 8%). We therefore suppose, that more tolerant of representative abiotic str essed of mentioned winter wheat cultivars seems to be the cultivar Zdar. On the other side, the Astella cultivar reacted sensitively to decreased pH, high temperature and drought. We observed that the more sensitive cultivars are cultivar Patria (decrease of energy content about 13.68%) and partial cultivar Plodna (decrease 10.10%) (Fig. 1). More tolerant to abiotic stress es seems to be the cultivar Olga (decrease of net energy 9.10%), as results from Fig. 1. The individual cultivars of wheat did not react to combustion of abiotic stress equally. The values of measured combustion heat are diff erent. In that case to some extent occurred influence of genotype, i.e. the ability of a certain cultivar to adapt towards unsuitable life conditions. We can agree with Golley (1961) and Hansen, Diepenbrock (1994) that energe tic value of plant material is the function of genotype and it depends on c onditions of external surroundings. That is why we suppose, that combustion heat values can to some extent represent one of the limiting factors for f inding out of adaptability of certain cultivars for abiotic stresses. Besid es the genotype and the variants of experiment, the influence of the year o f experiment and provenance of seeds participated in the amount of rich in energy matters accumulated into wheat grains, too. Comparing individual yea rs of experiment (Tab. III), it is possible to state that the seeds sown in 1997 had statistically significant lowest value of net energy. For instanc e, the control variant had in this year an average energy content 12.45 kJ. g(-1). On the contrary, statistically significantly highest average value o f combustion was exhibited by the seeds sown in 1999 (16.66 kJ.g(-1)). Abiotic stresses during growth and development of seeds influence basal met abolic paths and majority of seed characters. More detailed knowledge not o nly of anatomical construction of grains, but its physiological characters as well, including the amount of accumulated energy can serve as one of the factors, which can influence the choice of genotypes resistant to some abi otic stresses. Yield of grains was lower with the stressed variant compared with the control variant for 5.9 g per pot. The lowest yield was found wit h the sensitive cultivar Plodna (33.23 g) and the highest one was recorded by the more sensitive cultivar Olga (35.98 g). The tolerant cultivar, as fa r as the yield is concerned, seems to be the cultivar Patria, which decreas ed the yield among variants for 4.13 g (Tabs. I, IV).