Physiological and Transcriptomic Analysis of Shading Stress Responses in Calamus viminalis Seedlings

Light critically limits rattan seedling establishment. To elucidate adaptive mechanisms of Calamus viminalis under varied light, we conducted a 360-day pot experiment with four shading levels (0%, 20%, 50%, 75%), integrating morphological, physiological, antioxidant, and RNA-seq analyses. Moderate shading (20%) maximized seedling height (46.97 cm) and ground diameter (12.46 mm), increased net photosynthetic rate by 57.92% versus full light, and raised soluble protein/sugar while minimizing MDA and proline-indicating the lowest oxidative damage. Severe shading (75%) suppressed carbon fixation, reduced antioxidant enzymes, aggravated lipid peroxidation, and drastically lowered survival. Transcriptomics revealed intensity-dependent reprogramming: moderate shading activated phenylpropanoid/flavonoid defense pathways; severe shading upregulated photosynthesis/ribosomal genes but constrained overall carbon flux. Four core pathways (photosynthesis, hormone signaling, phenylpropanoid metabolism, carbon metabolism) coordinated shade responses-BR signaling upregulated (shade avoidance) while ABA downregulated under low light; light deprivation globally downregulated LHCB1 and rbcL, impairing capture/assimilation. We identify 20% shading as optimal for C. viminalis cultivation and reveal multi-level phenotype-physiology-molecule mechanisms, providing a theoretical basis for Calamus viminalis seedling nursery management under controlled nursery conditions.