The effects of light intensity, photoperiod, soil moisture potential, and temperature on bud morphogenesis in <i>Picea</i> species

Abstract

Environmental factors of bud morphogenesis in young spruce seedlings were investigated by inducing bud set, subjecting the plants to various treatments during bud formation, then counting the numbers of needle primordia formed when bud morphogenesis was complete. Ambient temperatures greatly influenced needle initiation; the optimum was at least 25 °C, and initiation was much slower at 20 and 15 °C. By contrast, light intensities between 3350 and 22 000 lx had little effect. There was no response to photoperiod between 6 and 15 h, but initiation was markedly reduced at less than 6 h. Responses to soil moisture potential were also weak, in the range of 0 to −900 kPa, although a delay in attainment of experimental treatment may have obscured a stronger influence. Bud morphogenesis retarded by unfavourable environmental conditions ceased at the same time as (or earlier than) morphogenesis under favourable conditions. The practical implications of a definite morphogenetic interval are discussed.