GROWTH RESPONSE OF THREE INDIGENOUS TREE SPECIES TO HORMONE AND SALT STRESS IN SOKOTO NIGERIA

Abstract

Seeds of three forest tree species namely Acacia senegal (L.) Willd, Balanites aegyptiaca (L.) Delile and Parkia biglobosa (Jacq.) were used to investigate the effect of different salinity (NaCl) and auxin (IAA) concentrations on germination percentage, stem height growth, collar diameter study and Relative Growth Rate (RGR). A factorial experiment in a completely randomised design was employed. 90 seedlings of the tree species were randomly divided into six treatment groups of 3 seedlings with five replicates. The experimental hormone at three levels of (0.0, 2.77 and 3.62μgg-1) and salt at two levels (2.2 and 2.8dSm-1) concentrations were respectively administered to each treatment for a period of twelve weeks. Result showed that seedlings administered with salt concentrations of 2.2dSm-1 and 2.8dSm-1 showed decrease in germination percentage, stem height growth, collar diameter and Relative Growth Rate. Similarly, results showed that increasing concentration of NaCl reduced germination percentage, stem height growth and collar diameter in the species. Auxin (IAA) decreased seed germination percentage in Acacia senegal (12%) and Parkia biglobosa (6%) at 2.8dSm-1, but increased seed germination in Balanites aegyptiaca (4%) at both levels tested, just as stem growth and collar diameter of the species were also influenced. Balanites aegyptiaca showed high seed germination percentage, stem height growth and collar diameter in comparison to other species studied. Treatment combination 0μgg-1/2.8dSm-1 was observed to be best for the growth of Acacia senegal, 2.77μgg-1/2.8dSm-1 for Balanites aegyptiaca and 2.77μgg-1/ 2.2dSm-1 for Parkia biglobosa. Parkia biglobosa was very susceptible to salt stress. These results showed that salinity is a major abiotic factor that influence auxin production and distribution, nutrient assimilation and shoot growth in the species tested. Parkia biglobosa should not be used in regeneration on high saline soils.