Shades and shapes: Influence of native shade tree canopies on internodal length, diameter and wall thickness in Pseudoxytenanthera stocksii (Munro) T.Q.Nguyen

The morphometric traits of plants growing under tree canopies often reflect intricate adaptations to microclimatic variations. Pseudoxytenanthera stocksii , a sympodial bamboo species, is traditionally cultivated in association with native shade trees in the Western Ghats, India. Despite its widespread cultivation, the influence of tree canopy cover on the culm’s morphometric traits remains unexplored. This study systematically investigated the influence of varying tree canopy cover – full shade (70–80% tree canopy cover), partial shade (30–50% tree canopy cover), and open environments – on internodal length, diameter, wall thickness and the diameter-to-wall thickness (d/w) ratio. Ten different sampling plots were identified within the natural distribution range of the species. Observations were recorded for two culms per clump across 120 clumps, resulting in a dataset of 240 culms (80 culms per treatment) with total 9120 observations recorded for primary variables. Culms growing under tree canopies achieved the longest internodal lengths, the largest diameters and the thickest basal culm walls, suggesting enhanced structural optimization in shaded environments. Internodal lengths increased with height, peaking at approximately 4 m from the ground level before declining, indicating a threshold beyond which treatment-specific effects became pronounced. In contrast, culms in fully open conditions exhibited the shortest internodal lengths, smallest diameters, thickest walls in lower - middle segments, and steepest tapering, likely due to direct exposure to sunlight and greater temperature fluctuations. The d/w ratio was highest in shaded culms, indicating greater internodal hollowness, especially in the mid-sections, while culms in open conditions showed the lowest d/w ratios, suggesting solid internodes. Across treatments, from full shade to open, d/w ratios exhibited a low–high–low trend along culm height, reflecting adaptive responses to achieve structural stability. These findings indicate a trade-off between structural integrity and vertical growth, emphasizing resource optimization strategies in P. stocksii under varying shade conditions and provide valuable insights for sustainable bamboo management under agroforestry systems. • Shaded conditions enhance internodal length and diameter in culms. • Internodal length differences become evident above 4 m height. • Higher d/w ratio in shade suggests greater internodal hollowness. • Open conditions show shortest internodes and smallest diameters. • Lower d/w ratio in open sites indicates more solid internodes.