Seed germination responses of four afromontane tree species to red/far-red ratio and temperature

Abstract

The germination response of Cordia africana, Juniperus procera, Acacia abyssinica, and Faidherbia albida seeds to continuous exposure of various red to far-red ratios (R/FR) and constant-temperatures of 15, 20, 25 and 30 °C were studied. Germination of C. africana seeds was strongly inhibited at low R/FR and it appears that this species has evolved a light quality sensing mechanism that prevents seed germination beneath leaf canopies. The germination probability of C. africana increased as temperature increased from 15 to 30 °C. R/FR, temperature, and their interaction significantly affected germination of J. procera. Seeds of this species displayed a complex dormancy mechanism and germinated only in a narrow range of temperatures and R/FR. The effect of R/FR on germination of J. procera was most pronounced and the highest germination probability was recorded at 20 °C. The germination probability of F. albida seeds increased with rising temperature (from 15 to 30 °C), but there was no significant effect of light. At high temperatures, mean germination time in this species decreased with increasing R/FR, but increased with rising R/FR at low temperatures. Neither R/FR, temperature, nor their interaction had a significant effect on the germination of A. abyssinica seeds. The results suggest that deep sowing of J. procera and especially C. africana seeds, as well as covering and shading of their seed beds with leaf litter in nurseries, should be avoided. By proper regulation of light and temperature conditions, prolonged nursery germination of J. procera seeds can be reduced.