Photosynthetic Activity of Fodder Grasses Under Conditions of Drought Stress

Crop performance is the results of genotypic expression modified by interaction with the environment. One of the environmental factors, that most widely limiting for the crop production is water. The deficit of water significantly limits the growth, development and yielding of crops. The paper presents a mini review of the own research results and the literature on the effect of water shortage on the rate of photosynthesis of forage grasses. A better understanding the physiological reactions of plants to water stress should improving irrigation efficiency, modifying plants for more efficient water use, and developing effective agriculture on dry area.

Photosynthesis rate of grasses under drought stress

The reduction in the intensity of photosynthesis in fodder grasses in drought conditions showed the results of own research and many authors. The [7] study showed a significant inhibition of this process in orchard grass (Dactylis glomerata), meadow fescue (Festuca pratensis), festulolium (Festulolium braunii) and Italian ryegrass (Lolium multiflorum) under long-term stress caused by water deficiency in the soil, but significantly less reduced intensity of this process in orchard grass and meadow fescue than Italian ryegrass and festulolium was shown, which indicates their greater resistance to stress. According to [8], the plant is resistant to stress if it is able to maintain physiological processes at the least changed level, in conditions different from the optimal ones. Therefore, the greater possibility of drought survival has those plants that have the ability to increase their tolerance to dehydration protoplast without disturbing its structure and vital functions. Also, the studies of [9] showed the smallest (statistically insignificant) decrease in photosynthesis intensity in conditions of drought stress in the orchard grass, while the greater (significant) in perennial ryegrass (Lolium perenne), timothy (Phleum pratense), tall oat grass (Arrhenatherum elatius) and meadow fescue. In turn, [10] showed a significant increase in photosynthetic intensity in the annual ryegrass (Lolium multiflorum var. westerwoldicum) grown in irrigated soil in a year characterized by shortage of rainfall in the growing season, which confirms its low resistance to drought.

The intensity of photosynthesis depends on many environmental factors, such as: type and intensity of light, temperature, concentration of oxygen and carbon dioxide in the air, water availability, but also on a number of internal factors such as leaf structure, chlorophyll content, enzyme activity, supply of mineral ingredients and plant development phase [3]. In the development of grasses, like other crop species, there are critical periods associated with greater sensitivity to water deficiency in the soil. In own studies [7], it was shown that with optimal soil moisture the studied grass species (orchard grass, meadow fescue, festulolium and Italian ryegrass) most intensively assimilated CO₂ in late tillering, shooting and earing phases, while about 30% less in flowering stage. In drought conditions, the highest decrease in the intensity of this process was noted at the end of the vegetative phase and at the beginning of shooting, which means that during this period the tested species were the most sensitive to water deficiency in the soil. The age of plants was also very important in the resistance of fodder grasses to drought. In the first year of vegetation, all tested grass species showed greater resistance to stress than in the second and third year of vegetation. According to [11] water deficiency causes the accumulation of proline in plant cells, which is a substance with anti-stress effect. The rapid accumulation of this amino acid affects the better efficiency of water intake from the soil and allows it to be kept longer in the plant. According to [12] accumulation of proline depends on many factors, but one of the most important is the age of the plant, therefore young plants in drought conditions accumulate more proline than older plants, in subsequent years of vegetation.

Knowledge about the physiological and genetic basis of grass reaction to adverse environmental factors is insufficient. The changing climate and the increasingly frequent dry periods indicate the need to conduct research aimed at understanding the reactions of various fodder grass species to unfavorable environmental factors, which will enable their selection and proper choice of species for appropriate habitat and regional conditions.

None.

No Conflict of Interest.

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