Together with auxins, cytokinins are the main plant hormones involved in many different physiological processes. Given this knowledge, cytokinin levels can be manipulated by genetic modification in order to improve agronomic parameters of cereals in relation to, for example, morphology, yield, and tolerance to various stresses. The barley (Hordeum vulgare) cultivar Golden Promise was transformed using the cytokinin dehydrogenase 1 gene from Arabidopsis thaliana (AtCKX1) under the control of mild root-specific β-glucosidase promoter from maize. Increased cytokinin degradation activity was observed positively to affect the number and length of lateral roots. The impact on morphology depended upon the recombinant protein's subcellular compartmentation. While assumed cytosolic and vacuolar targeting of AtCKX1 had negligible effect on shoot growth, secretion of AtCKX1 protein to the apoplast had a negative effect on development of the aerial part and yield. Upon the application of severe drought stress, all transgenic genotypes maintained higher water content and showed better growth and yield parameters during revitalization. Higher tolerance to drought stress was most caused by altered root morphology resulting in better dehydration avoidance.
A b s t r a c t. Due to the absence of a suitable method and standardized procedures, the root systems of plants have been evaluated to a much lesser extent than aboveground organs. The aim of this article is (i) to provide a detailed description and thus standardization of an upgraded procedure of electrical capacitance measurement for evaluating the size of the root system of plants in situ, which allows for a reassessment to be made during the growing season and subsequent harvest of seeds for the planting of selected progenies, (ii) to demonstrate, through a standardized methodological protocol, the applicability of root electrical capacitance measurement as a field phenotyping method for the selection of superior root systems to improve crop abiotic stress tolerance and resource efficiency, (iii) to suggest a standardized methodological protocol for the application of electrical capacitance measurements in breeding nurseries, and (iv) to discuss the methodological aspects, development and limitations of this method. A methodological overview of the use of electrical capacitance to measure plant root systems, which emerged from working groups directed by the author of this unique method, is presented along with a standardized protocol. An overview of the application of electrical capacitance measurements of roots in breeding is shown along with some examples of successful applications.K e y w o r d s: root system, drought tolerance, varieties, yield
Differences in transpiration of maize (Zea mays L.) plants in four soil moisture regimes were quantified in a pot experiment. The transpiration was measured by the "Stem Heat Balance" method. The dependence of transpiration on air temperature, air humidity, global solar radiation, soil moisture, wind speed and leaf surface temperature were quantified. Significant relationships among transpiration, global radiation and air temperature (in the first vegetation period in the drought non-stressed variant, r = 0.881**, r = 0.934**) were found. Conclusive dependence of transpiration on leaf temperature (r = 0.820**) and wind speed (r = 0.710**) was found. Transpiration was significantly influenced by soil moisture (r = 0.395**, r = 0.528**) under moderate and severe drought stress. The dependence of transpiration on meteorological factors decreased with increasing deficiency of water. Correlation between transpiration and plant dry matter weight (r = 0.997**), plant height (r = 0.973**) and weight of corn cob (r = 0.987**) was found. The results of instrumental measuring of field crops transpiration under diverse moisture conditions at a concurrent monitoring of the meteorological elements spectra are rather unique. These results will be utilized in the effort to make calculations of the evapotranspiration in computing models more accurate.
SummaryThe development of seeds at various positions in the pod is asynchronous. Thus, the differences of seed dry mass production because of environmental conditions may depend on the cultivar type, type of inoculants and interrelations between seeds per pod, pods per plant or seeds per plant. Presently, a mathematical description of pea seed categorisation is missing. The aim of the study was the assessment of two groups of variables (quantitative and qualitative) for pea seed weight categorisation by ordinal regression model. Year, cultivar and inoculant constituted the first group (qualitative variables), whilst seeds per pod, the pods per plant and seeds per plant (quantitative variables) were entered as covariates in the ordinal regression model. According to the ordinal regression model variables, seeds per pod, pods per plant, seeds per plant, year and cultivar are meaningful predictors of the seed mass categories. However, the variable inoculant is marginally significant. Keywords
The stress reaction of maize plants was evaluated in relation to drought stress intensity and to growth stages by assessing the transpiration intensity and the expression of two dehydrin genes, DHN1 and DHN2. The maize plants were grown under four different watering conditions: well-watered (control), mild stress, moderate stress and high stress. The sap flow values were taken as an indicator of plant stress reactions at the transpiration level. A significant correlation between the average diurnal values of sap flow and the volumetric soil moisture appeared only for the moderate stress condition (R = 0.528) and for the high stress condition (R = 0.395). Significant increases in the expression of DHN1 and DHN2 (DHN1 = 10 5 -fold and DHN2 = 10 3 -fold) were observed primarily for the high stress condition compared to the control. Differences in the stress reactions at the DHN1 gene expression level were detected for all the experimental drought stress conditions. A relatively close relationship between the levels of expression of both genes and the values of the sap flow was observed during the initial stage of the stress (R = -0.895; R = -0.893). The severity of water stress and transpiration intensity significantly affected certain biometric and yield parameters of maize. Higher DHN genes expression at the ripening stage was related to lower grain and dry biomass yield. The results indicated that DHN gene expression assessment in maize and evaluation of the changes in transpiration expressed by the sap flow could be considered appropriate indicators of stress intensity while the DHN gene expression assessment appeared to be more sensitive than evaluation of the changes in transpiration, mainly in the initial phases of stress response.
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