The dissertation is devoted to the study of the participation of the components of antioxidant and osmoprotective systems in rye, wheat, and triticale in the adaptation to low temperatures, and to the study of these systems’ induction by gasotransmitters nitrogen oxide NO and hydrogen sulfide H2S, and phytohormone salicylic acid.
In the work, changes in the functioning of antioxidant and osmoprotective systems at low-temperature hardening of grain cereals were shown, which indicates their importance in adapting to hypothermia; species and varietal characteristics of these systems were identified and the possibility of their induction and increase of frost resistance of plants through the application of H2S and NO donors, and phytohormone salicylic acid were shown.
The main experimental objects were etiolated seedlings of soft wheat (Triticum aestivum L., variety Doskonala, winter, frost-resistant), rye (Secale cereale L., variety Pamyat' Khudoerka, winter, frost-resistant), and triticale (×Triticosecale Wittmack, frost-resistant winter varieties Raritet and Buket, and non-frost-resistant facultative (‘dvuruchka’) ones Alexandra and Pidzymok Kharkivskiy). Hardening of seedlings was performed for 6 -7 days at a temperature of 2-4°C. Hardened and unhardened seedlings were subjected to freezing at temperatures of -5 or -9°C, and their survival was determined.
In a series of experiments to study the effect of H2S on the resistance of seedlings to negative temperatures, sodium hydrosulfide (NaHS) in concentrations range of 0.025–1 mM was added to the medium at the beginning of seed germination and on the third day.
In the experiments to study the NO effect on frost resistance, seeds were primed with NO donor by immersion to the sodium nitroprusside (Na2[Fe(CN)5NO], SNP) solution in concentrations range of 50-200 µM. In the series of experiments on the salicylic acid and SNP combined effects, seeds of the studied variants were immersed in a solution containing 10 μM salicylic acid and 100 μM SNP.
The paper compares the performance indicators of the antioxidant and osmoprotective systems of etiolated seedlings of winter rye, triticale, and wheat in physiologically normal conditions and after cold hardening, high peroxidase activity and proline content make a greater contribution to the rye adaptation to hypothermia, and triticale has a high content of flavonoids and sugars. At the same time, in wheat the activity of the antioxidant enzymes SOD and catalase changed more significantly after hardening.
In a series of experiments with different varieties of triticale, a relationship was established between the frost resistance and the state of antioxidant system.
After hardening of seedlings of frost-resistant triticale varieties Buket and Raritet at 2-4°C for 6 days, the activities of SOD and catalase increased, and in less resistant Alexandra and Pidzymok Kharkivskiy changed less significantly. At the same time in this varieties the activity of guaiacol peroxidase increased more markedly.
The hardened seedlings of Buket, Raritet, and Alexandra varieties had a much higher sugar content than the Pidzymok Kharkivskiy variety. The content of proline in response to hardening increased in all varieties, while the absolute values in the varieties Buket, Raritet, and Pidzymok Kharkivskiy were higher than in the variety Alexandra.
It was found that there is a fairly strong correlation between the frost resistance of seedlings and adult plants of wheat, rye and triticale (r = 0.78, P ≤ 0.07. However, a strong correlation was observed between the integral normalized index, which consisted of the sum of normalized values of antioxidant enzyme activity and the content of low-molecular-weight protectors in hardened seedlings, and frost resistance of seedlings (r = 0.94, P ≤ 0.01) and plants in the tillering phase (r = 0.90, P ≤ 0.05), and their frost resistance. This integral index can be used as a marker of frost resistance of winter cereals to identify resistant genotypes.
A comparative study of the exogenous H2S effect on resistance of wheat and rye seedlings to cryostress was conducted. Treatment of unhardened seedlings with NaHS at concentrations of 0.1 and 0.5 mM caused an increase in their survival after freezing at -5°C.
Priming of rye and wheat seeds by 0.1-0.2 mM SNP increased their hardening ability.
The increase in the seedlings’ survival after freezing due to priming of seeds was shown as a result of priming seeds with 10 μM salicylic acid, and combined treatment with 10 μM salicylic acid and 100 μM SNP enhanced the protective effect.
Thus, donors of gasotransmitters hydrogen sulfide and nitrogen oxide, as well as plant stress hormone salicylic acid, can have a cryoprotective effect on cereals, activating a signaling network and enhancing the functioning of antioxidant and osmoprotective systems when plants adapt to cold.
