Drought Tolerance Of Garcinia kola And Garcinia afzelii At The Seedlings Stage

Abstract

Garcinia kola and Garcinia afzelii are very useful forest tree species for chew stick and medicinal purposes in West Africa. They are currently receiving attention for cultivation due to the dwindling stocks of the species in the natural forest. Soil moisture is one of the most critical environmental factors that affect seedling growth in the field. The study was therefore conducted to test the response of the two species to variability in water availability. The seedlings were subjected to simulated no drought, 15-day drought, 30-day drought and 84-day drought. Seedling response to watering after 60-day simulated drought by withholding of watering was also monitored. Relative growth rate (RGR) in diameter decreased with the prolongation of the simulated drought period, and the difference was significant among all the treatments. For G. afzelii, simulated 84-day drought exhibited negative RGR in diameter, whereas for G. kola both the simulated 30-day and 84-day drought exhibited negative RGR in diameter. The RGR in height and leaf production was similar for the simulated no drought and the 15-day drought but significantly different from the 30-day and the 84-day drought period for G. afzelii. However for G. kola, it was the 15-day and 30-day simulated drought that were similar. Leaf production was highly correlated with height growth than with diameter growth. Release of drought-stress by the resumption of watering triggered leaf shedding up to a minimum value and thereafter increased. The relative rate of leaf production after re-watering increased, however the rate declined with the passage of time for G. afzelii but continued to increase for G. kola. Diameter growth was more affected than height by the dry conditions. The growth performance of G. afzelii was generally better than that of G. kola and both species have mechanisms for overcoming dry periods without experiencing mortality. Garcinia afzelii can be established in any of the forest zones, whereas Garcinia kola should preferably be established in Wet/Moist Forest and moist semi deciduous forest zones.

Keywords: Garcinia species, simulated drought, diameter growth, height growth, leaf production