Seasonal changes in the content of plastid pigments in the hametophyte of dominant mosses in forest ecosystems of Ukrainian Roztochchya

Abstract

Poikilohydric mosses, as one of the most sensitive groups of plants to the influence of habitat conditions, responding to environmental factors, demonstrate adaptations, which differ from vascular plants, for the prediction of changes in the natural environment. The changes in the content of photosynthesis pigments and their ratio in dominant deciduous epigeal species of mosses depending on changes in stand crowns, insolation intensity, water-temperature regime of soil and air in local ecosystems of Ukrainian Roztochchya were analyzed. Due to the significant projective cover and closed crowns in the area of ancient forests, the 30-50% lower indicators of light intensity, 8-12% of substrate temperature under moss turf, and 43-50% higher indicators of its humidity compared to pine plantations were identified. Anthropogenic impact in the area of stationary recreation was conditioned by the intensive trampling, which led to a decrease in the closure of the tree crowns (up to 0,4-0,5), an increase in light intensity by 2,5 times, and a decrease in soil moisture under moss turf by 2-4 times. The shade-tolerant Polytrichastrum formosum, Atrichum undulatum and Plagiomnium affine mosses compensated the limited amount of light energy available for growth by intensively increasing of the content of pigments (chlorophylls a and b), light-harvesting complexes and reducing of the chlorophylls a/b ratio to 1,6-2,1. A significant variability in the ratio of chlorophylls to carotenoids from 5 to 9 was found. Significant limits of variation in the content of carotenoids and the ratio of chlorophylls to carotenoids served as an indicator for assessing the edapho-climatic changes in the living conditions of bryophytes in forest ecosystems. Significant variability in the ratio of chlorophylls a/b (2,35-4,25) in autumn in comparison with such indicators in summer is associated with increased illumination of the experimental areas and the activity of the reactions of mutual transformations of chlorophylls a and b. The increase in the values of the ratio of chlorophylls a/b caused by the activation of pigment metabolism indicates their adaptation to both light and shadow. In autumn, the decrease in the ratio of chlorophylls to carotenoids (in the range of 4,31-5,08) is associated with the intensity of synthesis and decomposition of chlorophylls a and b, and carotenoids, which can be used as an important indicator of plant adaptation ability to the changes in light intensity, humidity, and temperature.