FREE AMINO ACID COMPOSITION IN SCOTS PINE TISSUES UNDER STRESS IMPACT IN RHIZOSPHERE

The free amino acid content in the needles and the inner bark of stems and roots of 8-13-ages self-sawn trees of Pinus sylvestris L. in Central Siberia in experimental and natural conditions was compared. The experiments imitated an influence of long-seasonal or permafrost, soil drought and root hypoxia, concomitant flooding. The aim of the investigation was to expose the adaptive changes of these metabolites composition under stress impact. All of types of stress influences changed the total free amino acid content in the tissues of different morphological tree parts: the cooling of root system caused a deposit of free amino acids in overground tree part, the water deficit stimulated an accumulation of free amino acids in root inner bark, the flooding decreased the amino acid content in all tissues. The ratio in a group of amino acids with glutamic acid as metabolic precursor (-aminobutyric (GABA), proline, arginine, citrulline and ornithine) changed under different stress impact. The cold stress in rhizosphere caused GABA accumulation in the needles and stem but not in the roots in the period of soil thawing. The moderate moisture deficit had not an influence on GABA content, the flooding caused GABA accumulation only in new needles. The maximal exceeding above control were marked for the sum of arginine and its metabolic precursors citrulline and ornithine. The group of these compounds may be considered as stress metabolites for scots pine, but specificity of depositing of these amino acids at water stress requires additional proofs. Since the proline accumulation was showed in separate times in the different tissues under all of investigated stressors impact, the specificity of proline as indicator of water stress in scots pine tissues is debatable. The disturbance of donor-acceptor connections in experiment with cooling resulted to the amino acid accumulation in stem inner bark, in experiment with drought – in root inner bark

Drought impact on wood formation and antioxidant protection of Scots pine cambial zone

The effect of drought on the 8-9-year-old seedlings of Scots pine (Pinus sylvestris L.) was simulated in the field by isolating trees from precipitation. The biochemical changes typical of water stress wеre compared with the structural changes of the annual rings of wood. The samples of the current and last year needles, cambium and adjoining layers of xylem and phloem of stems and roots were analyzed. In the needles, the content of chlorophyll a and b and carotenoids were determined. The contents of hydrogen peroxide and malondialdehyde (MDA), the activity of enzymes, realizing antioxidant protection: superoxide dismutase (SOD), peroxidase, glutathione reductase and content of sugars and starch were determined in tissues of xylem, phloem and cambium. It was shown that drought reduces the weight of the needles, the chlorophyll content and the width of the annual wood rings. In moderate drought in the cambial zone oxidative stress was developed and also protection system against free radicals was activated, which resulted in a high SOD activity and the accumulation of hydrogen peroxide due to the activity of peroxidase reduction. As a result, the division processes in cambial zone and cells extension growth were inhibited and the width of annual wood rings decreased due to reduction in the number and size of tracheids. It was found that decrease in growth was not due to deficit of carbohydrates for the process xylogenesis. Water deficit increases the concentration of low molecular weight carbohydrates in the tissues, which, due to the inhibition of division and extension cambial derivatives are only partially used for thickening tracheid cell walls. As a result, abnormal tracheides with reduced size of cells and lumens and thickened cell walls were formed. Abundance of soluble carbohydrates was deposited as a reserve pool in the root phloem in the form of starch. The stock function of root phloem was increased under water deficit conditions

Fluorescence methods for estimation of post-fire response of pine needles

Forest fire represents one of the most serious abiotic stress factors that influence the function and productivity of ecosystems globally. Siberian pine forests are often exposed to forest fires, but they are not always harmful to them. This paper discusses the possibility of using fluorescent methods to assess the thermal effects on the assimilation apparatus of Scots pine (Pinus sylvestris L.) needles. The assimilation apparatus of pine needles was reestablished after exposure to convective, simulating the effect of ground fire heat flow, though the recovery rate depends on the impact force. The analysis of fast and delayed fluorescence characteristics revealed differences in the thermostability of the Scots pine needles showing certain modification of physiological processes in plants under the influence of stress factors with a positive acclimation effect. The Scots pine needles grown after ground fire are more resistant to the recurrent sublethal temperature, and this effect is maintained during the next growing season. This paper suggests that reforestation planning, particularly burning (low-intensity fire), will result in improved tree physiology that will lead to an increase in Scotch pine survival rate due to repeated heat stresses. Furthermore, the fluorescence method can be used to diagnose the thermic resilience of pine needle and assess high-temperature effects

Thermostability of antioxidant enzymes in tissues of Scots pine in heat shock conditions

Samples of needles from the middle part of the crown and cambial zone scrapings, which includes cambium cells and nonlignified xylem cells from five stems of 15 years old Scots pine Pinus sylvestris L. trees from green moss-forb groups stands on sod-podzolic soil in Krasnoyarsk forest steppe were investigated. Thermal stability of the antioxidant enzymes: superoxide dismutase (SOD), peroxidase, catalase, glutathione reductase (GR); enzymes of carbohydrate and phenolic metabolism: amylase, invertase and phenylalanine ammonia-lyase (PAL) which are involved in providing the xylogenesis process; and markers of oxidative stress: peroxide hydrogen and malondialdehyde (MDA) were studied in the temperature interval 20–80 °C. It was found that the positive effect on the antioxidant enzymes activity mainly manifested up to 40 °C. As the temperature increases, antioxidant protection weakens. The mechanisms of oxidative stress in cambium zone and needles in condition of pyrogenic heat shock are distinguished due to different thermal stability of antioxidant enzymes in these tissues. The most sensitive to elevated temperatures was catalase both in cambium zone and needles. In the cambium zone, peroxidase and GR detect low resistance to high temperature, while SOD has a higher level of. In the needles on the contrary, peroxidase and GR exhibit high thermal stability, whereas SOD activity rapidly reduces at higher temperatures. Amylase, invertase and PAL exceed, according to the thermal stability of examined antioxidant enzymes, what allow quick restoration of carbohydrate and phenolic metabolism after pyrogenic heat shock to providing of xylogenesis process