Effect of moisture and light intensity on the early growth of miracle berry (Synsepalum dulcificum (Schum. & Thonn.) Daniell): a threatened tropical shrub species

Abstract

Synsepalum dulcificum is a highly valued ethnobotanical shrub, whose wild populations are threatened by over exploitation and habitat destruction. In this study, the effect of different light intensities and watering regimes on early growth of Synsepalum dulcificum were investigated for 24 weeks. In a completely randomised design experiment with factorial arrangement, uniformly growing seedlings were potted and subjected to four light intensities (25%, 50%, 75% and 100%) and four watering regimes (daily, 3-day, 5-day and 7-day intervals). The seedling total height, collar diameter and number of leaves were measured, fortnightly. The relative growth rate, absolute growth rate and net assimilation rate were also determined. Data were analysed using descriptive statistics and ANOVA at p < 0.05 level of significance. There were significant differences in the main and interaction effects of light intensity and watering regime on the growth variables. The combined effect of light intensity and watering regime revealed that 100% light intensity and watering at 7 days intervals had the highest leaf production (12.00±1.58). Seedling height increased from 6.5±0.1 cm (75% light intensity) to 6.99±0.01 cm (25% intensity). Daily watering (7.19±0.1 cm) had the highest seedling height while 7-day watering (6.39±0.1 cm) was least. The lowest collar diameters were for 75% light intensity (1.25±0.02 mm) and 3-day watering intervals (1.42±0.02 mm). The relative growth rate increased from 1.06x10^-2 month^-1 (25% light intensity) to 2.10x10^-2 month^-1 (75% light intensity), and 1.22x10^-2 month^-1 (7-day watering) to 2.41x10^-2 month^-1 (3-day watering), respectively. Synsepalum dulcificum seedlings grew successfully at 25% light intensity and could survive for seven days without watering.