GERMINATION AND STORAGE OF VINCA SEED IS INFLUENCED BY LIGHT, TEMPERATURE, AND RELATIVE-HUMIDITY

Light, temperature, relative humidity (RH), and GA, affect vinca [Catharanthus roseus (L.) G. Don] seed storage and/or germination. GA3 failed to increase the germination percentage in darkness but significantly increased the percentage in continuous light. Similarly, GA3 treatment reduced both the number of days required to achieve 50% of the final germination percentage (T50) and the span between 10% and 90% germination (T90 - T10) for seeds in light, but not in darkness. Germination percentages were maximal and about equal at 25, 30, or 35C in darkness; germination was lowest below 25C. Germination T50 and T90 - T10 required the fewest days between 25 and 35C. Reducing seed moisture from 9.9% to 3.9% increased the T50 from 2.4 to 3.0 days but failed to change germination percentages. Germination percentage declined linearly as seed storage temperatures were reduced from 5 to -20C, whereas days to T50 increased. Seed storage for 12 months without reduction in germination percentage was possible at 5C and 11%, 33%, or 52% RH, but storage at 75% or 95% RH for periods exceeding 1 month reduced germination. Seeds stored at 33% or 52% RH required fewer days to T50 than did seeds stored at 11%, 75%, or 95% RH. Chemical name used: gibberellic acid (GA3).