INFLUENCE OF ENVIRONMENTAL FACTORS ON MERISTEM ACTIVITY AND STABILITY IN MATURE-PHASE HEDERA HELIX PLANTS

Abstract

ABSTRACT Mature-phase Hedera helix L. plants were subjected to different environmental conditions in growth chambers in order to determine the factors ensuring the maintenance of a strictly vegetative growth with foliar leaf production. At a temperature of 24°C and at a light flux of 20,000 lux (300 μ E m−2 s−1) photosynthetically active radiation (PAR), inflorescence initiation was inhibited under both long days (LD) and short days (SD); however, in about 50% of the plants the meristems became quiescent for a short period. During later development, these meristems, as well as those of the remaining 50% of the plants, became unstable resulting in plants with distichous phyllotaxis and other juvenile characteristics. At 21°C and at the same light flux, a high percentage of the plants became quiescent or formed at least some scale-type leaves. When relative humidity (R.H.) was maintained at 100%, the proportion of quiescent plants was lower than at ambient humidity (50–70% R.H.). At 24°C and under SD, the d...