ABSTRACT
Response of Plants to Acetylcholine and Biogenic Amines 2.1. GROWTH, DEVELOPMENT AND MOVEMENTS OF PLANTS 2.1.1. Growth The physiological role of acetylcholine in plants was first investigated by Jaffe (1970). He found that this substance acts on the plant growth reac tions controlled by phytochrome. The effect of acetylcholine on growth of plants is demonstrated in Table 10. Most often it stimulates the elonga tion of coleoptiles and hypocotyls of seedlings but has no effect on
Table 10. The effects of acetylcholine on the growth reactions
elongation of etiolated seedlings. In three cases an inhibition of the growth of root tips and secondary roots or the formation of secondary roots was noted. The formation of secondary roots in Phaseolus aureus and Pisum sativum was observed only in plants grown in the light. In the concentra tion range 0.1-500 pM, acetylcholine accelerated the growth of apical segments of coleoptiles of wheat Triticum vulgare by 20% (Lawson et aL, 1978). Exposure to red light at 660 nm caused an elongation of the seg ments by 62% compared to control. The addition of acetylcholine 30 min. after switching on of the light decreased the rate of the process by 50%. It should be noted that marked changes in growth processes were induced only by high concentrations of acetylcholine (> 10"3 M). The effect was no more than 20-30% of the control and mainly within the standard devia tions. Unlike in higher plants, in moss Athyrium filix-femina, low concen trations of acetylcholine (lCT^-lO-5 M) sharply stimulated the elongation of protonema (Bahre, 1975).
