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Effects of exogenous bacterial quorum-sensing signal molecule/messenger N-hexanoyl-L-homoserine lactone (C-HSL) on acorn germination and plant growth of Quercus robur and Q. rubra (Fagaceae)

The effect of pre-sowing priming with N-hexanoyl-L-homoserine lactone (C6-HSL) solution (300 mg/L) on acorn germination and morpho-phenological characteristics of Quercus robur and Q. rubra was studied under laboratory conditions. After priming, 93.4% of Q. robur acorns germinated that exceeded the control by 32.2%, while the number of sprouted acorns of Q. rubra increased within error limits by 5% more than the control and amounted to 90%. According to morphological characteristics, the 47-day-old plants of Q. robur were divided into the following groups: germinated acorns, sprouts and seedlings with juvenile leaves, whereas among the plants of Q. rubra, sprouts and seedlings with true leaves were selected. A group of plants with juvenile leaves was detected only in the samples primed with C6-HSL. Priming induced differential changes in cotyledon biomass of both species and accelerated nutrient utilization by Q. robur seedlings. We observed a positive effect on the growth and biomass accumulation of Q. robur plants and a negative effect, except for plants of the third group, on those of Q. rubra. The dry weight of seedling roots of Q. robur and shoots of Q. rubra increased, respectively, by 103% and 153%. Priming of acorns with C6-HSL solution induced an increase in number, length, biomass and total area of leaves. These changes were more pronounced in Q. rubra seedlings. Alterations in the root system architecture towards formation of numerous additional lateral roots were recorded for both species. Thus, priming with C6-HSL solution activated acorn germination and stimulated growth of Q. robur plants and decelerated growth of plants of Q. rubra. Exogenous C6-HSL did not eliminate the syndrome of unfriendly seedlings of both studied oak species, but improved the viability of acorns and increased the number of seedlings.