Sugar-palm (Arenga pinnata (Wurmb.) Merr.) grows naturally under the shade of tree canopies and therefore, shading levels have a main role for its optimal growth. This study was conducted in order to examine the effects of shading on the seedlings growth for up to 11 months under four shading levels: S0 (100% of full sunlight or non-shading), S1 (32% shading level), S2 (56% shading level), and S3 (64% shading level). Sugar-palm seedlings grown under the shade (i.e. 32, 56, and 64%) showed better plant height, stem diameter, leaf size, petiole and rachis lengths, chlorophyll content, fresh and dry root weights, root volume, and total biomass than those grown in direct sunlight. Although there were no significant different responses among the shading treatments on plant height, biomass dry weight, leaf morphological characteristics, chlorophyll content, and SPAD value, the S2 treatment had a significant effect on a better root characteristics. Therefore, it can be concluded that this treatment, i.e. 56% shading level, is the optimal condition for sugar-palm seedlings.
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