EFFECT OF LIGHT AND SOIL NUTRIENT ON SEEDLING MORPHOLOGY OF Syzygium SPECIES OF A LOWLAND RAIN FOREST IN SRI LANKA

Abstract

Knowledge or how light and soil nutrient availability affect seedling morphology inrelation to seedling growth is critical for understanding the regeneration establishment ofseedlings beneath rain forest canopies. This study measured changes in seedlingmorphology or four related tree species in the family Myrtaccae in relation to differingcombinations of light and soil nutrients. Species selected were canopy and sub canopytrees or rain forest in southwest Sri Lanka.

Shelters were constructed in the full open that created light treatments representing a rangeof photosynthetic Photon Flux Densities (PFD) and red: r:u' red ratios found in the rainforest. Within each shelter seedlings were Icrtiliscd with phosphorous. potassium andmagnesium nutrients. Newly germinated seedlings of each of four species (S. firntum, S.makul , S. opcrculatum, S'. rubicuudumv were grown for one and half years after which theywere dug up and measured for. shoot length. root length. root collar diameter. leaf number.leaf area. and dry masses of roots. stems and leaves.

Shoot length and leaf area auaincd maxima in shelters simulruing large forest openings(400nh. Root length. root collar diameter and dry masses gain were highest in full suntreatment. Compared with nutrient treatments phosphorus promoted greatestmorphological measurements for all species. The results suggest that these species exhibitgreater morphological responsiveness to increase in irradiancc and to addition ofphosphorous Icrtiliscr.