Responses of growth and chlorophyll fluorescence of gmelina arborea roxb. ex sm. to light are not influenced by mild moisture stress in non-nitrogen-limited soil

To examine the combined effects of soil moisture and nitrogen availability on the responses of growth and chlorophyll fluorescence to light, seedlings of Gmelina arborea were grown under full sunlight or 50% sunlight, four moisture regimes (M1: 20-30%; M2: 40-50%; M3: 60-70%; M4: 80-90% field capacity) and four nitrogen levels (N1: 3 g/kg; N2: 3.75 g/kg; N3: 4.5 g/kg; N4: 5.25 g/kg) for six months. Full sunlight suppressed height and stem volume whereas it increased biomass production. Moisture elevation augmented morphological traits and biomass production while reducing root: shoot. Height, leaf count, stem diameter and volume were decreased by nitrogen increase. A 2-factor interaction indicated that the increase in height by shading was limited to M2, M3, and M4. Similarly, M1 counteracted the beneficial effect of full sunlight on root biomass. Another interaction revealed that only seedlings in N1 and/or N2 experienced the increase in morphology induced by moisture elevation. Minimum fluorescence yield, maximum quantum yield of PSII and maximum primary yield of photochemistry of photo system II were insensitive to treatments. No 3-way interaction was detected, suggesting that the responses of Gmelina arborea to light may not be constrained by the M×N interaction.