Influence Of Vertical Soil Moisture To Root Growth And Biomass Allocation In Acacia Senegal Linn Seedlings From Two Provenances

Acacia senegal is an important drought-tolerant species, but limited information exists on how vertical soil moisture affects its early growth from different provenances. Uneven moisture distribution in drylands may influence root development and biomass allocation, affecting seedling establishment. Therefore, this study aims to investigate the influence of vertical soil moisture gradients on root growth and biomass allocation in Acacia senegal seedlings from two provenances, to determine best provenance and moisture condition for survival. Study was conducted in the greenhouse at Federal University Dutse using 36 glass-fronted rhizotrons (120 x 30 cm) filled with 7 kg sieved sandy-loam topsoil. Acacia seeds from provenances were germinated and transplanted into rhizotrons arranged in Randomized Complete Block Design with watered and 10% drought treatments. Shoot and root lengths, soil moisture at four depths, and biomass at three soil sections were measured for 56 days. Drought significantly reduced shoot length in species, with Nguru provenance showing greater shoot inhibition than Gujba. Root length increased under drought, with Nguru developing significantly longer roots (122.00 cm) than Gujba, indicating a drought-avoidance strategy. Root dry weight was highest in the 0–40 cm depth, and Nguru had greater total root dry weight and higher root:shoot ratios across treatments. Lateral root number varied by depth and provenance, decreasing with soil depth. Water uptake shifted progressively downward as upper layers dried, with root distribution patterns matching water extraction. Nguru (arid) provenance exhibited stronger stomatal closure and deeper rooting, suggesting superior drought adaptation through enhanced water acquisition and reduced transpiration. Nguru provenance showed superior drought adaptation through deeper roots and higher root:shoot ratio, while Gujba maintained greater shoot growth.