Effect of Prolonged Geo-stimulation and Presence of 32P on the Elongation of Lateral Shoots of Decapitated Pea Seedlings

The effects of prolonged geo-stimulation and presence of ³²P on 3-leaf decapitated pea (Pisum sativum L. cv. Alaska) seedlings were studied with regard to lateral bud elongation as well as accumulation and recovery of isotope. Prolonged geo-stimulation favoured the dominance of basally located, upwardly directed buds and suppressed the elongation of subapical bud — a gravimorphic response similar to the one shown by intact geo-stimulated branches of woody plants. Basal bud 2 was an exception as it dominated both in the above- and below-axis position. Accumulation of ³²P in buds was the result of their own growth, whereas in the other parts of the seedlings accumulation of isotope was not necessarily related to growth. Geo-stimulation affected ³²P recovery in redistribution experiments, whereas it had no effect in distribution experiments. In the former, the decrease in the isotope level in the seedling suggests a loss of ³²P. Prolonged presence of ³²P in the seedlings had a deleterious effect on bud elongation.