葉片角質蠟層對藍莓光合生理之影響

Abstract

本研究旨在探討葉片角質蠟層(epicuticular wax)對藍莓(Vaccinium spp.)葉片光合作用效率與環境適應性之影響。葉表蠟質能限制太陽輻射、降低葉溫以提升逆境調節能力，也可能對氣體擴散路徑造成阻礙，進而影響光合作用速率。由於台灣夏季氣候高溫高濕，對於蠟質含量高品種而言，光合作用速率可能因現氣體擴散受限而降低，反之亦可能因環境逆境減少而增加。因此，本試驗以蠟層豐厚之兔眼藍莓(V. virgatum)品種 NTU025 與蠟層較薄之南方高叢藍莓(V. corymbosum hybrid)品種Blue Muffin (BM)為材料，分為對照組(NTU025)、黏土去蠟處理(NTU025-C)、擦拭去蠟處理(NTU025-TIS)以及低蠟品種(BM)等四組處理，測量葉色、葉片氣體交換、葉溫、螢光、光反應曲線與CO2反應曲線。再以Farquhar, von Caemmerer and Berry (FvCB) model 分析及比較可能影響光合作用的因子。結果發現去除蠟質顯著提升NTU025之氣孔導度(gs)與蒸散速率(E)，並伴隨細胞間隙CO2 濃度(Ci)上升，反映氣體擴散效率的改善，但水分利用效率(WUE)則呈下降趨勢。皮爾森相關分析亦顯示葉片亮度(L*)與蠟質呈正相關，但與gs、E、Ci呈顯著負相關；葉肉導度(gm)於各處理間無顯著差異。整體而言，在無環境逆境的狀態下，gs為主要擴散限制來源，gm影響相對較小。在光反應方面，去除蠟質後，光合作用系統PSII 穩定性與光能調控能力下降，導致電子傳遞鏈速率(Jmax)下降。在去蠟處理 NTU025的葉片，雖然擴散提升，但 PSII受光傷害風險增加，造成 Jmax明顯低於 BM，進而限制 RuBP 再生與光合作用速率。與之相對，BM 處理組在維持高 gs的同時亦展現更佳的 Jmax，顯示其具備平衡擴散與光保護的機制。

This study aimed to investigate the effects of epicuticular wax on photosynthetic efficiency and environmental adaptability in blueberry (Vaccinium spp.) leaves. Leaf wax layers can enhance stress tolerance by reflecting solar radiation and reducing leaf temperature. On the other hand, they may also obstruct gas diffusion pathways, potentially limiting photosynthetic efficiency. In the hot and humid summer climate, photosynthesis of cultivars with thick-wax may be reduced by constrained gas diffusion, or oppositely, may be improved due to reduced stress. Therefore, this study utilized two blueberry cultivars with differing wax characteristics: NTU025, a rabbiteye blueberry (V. virgatum) with a thick wax layer, and Blue Muffin (BM), a southern highbush blueberry (V. corymbosum hybrid) with thin wax. Four treatment groups were established: a control group (NTU025), clay-dewaxed (NTU025-C), tissue-wiped (NTU025-TIS), and low-wax genotype (BM). Leaf color, gas exchange, leaf temperature, chlorophyll fluorescence, light response curves, and CO2 response curves were measured. Key photosynthetic parameters were analyzed using the Farquhar, von Caemmerer, and Berry (FvCB) model. Wax removal significantly increased stomatal conductance (gs), transpiration (E), and intercellular CO2 concentration (Ci), indicating enhanced diffusion capacity. However, water use efficiency (WUE) declined. Pearson correlation analysis showed significant negative correlations between leaf brightness (L*) wax content, gs, E, and Ci, confirming that higher wax content restricts gas diffusion. Mesophyll conductance (gm) showed no significant variation, indicating that in normal conditions without stress, stomatal limitations dominated. Analysis of diffusion limitation partitioning confirmed that gs, rather than gm, was the primary constraint on CO2 diffusion. In terms of photochemistry, wax removal compromised PSII stability, leading to reduced electrontransport rate (Jmax). In the dewaxed NTU025 treatments, despite the improved CO2 diffusion, Jmax declined significantly, likely due to increased photodamage risk without wax protection. In contrast, BM maintained both high gs and superior Jmax, suggesting an intrinsic ability to balance diffusion and photoprotection, possibly via better energy regulation or higher chlorophyll content. Overall, the results indicate that under non-stressed conditions, epicuticular wax primarily impedes gas exchange rather than offering thermal advantages. Photosynthetic outcomes are ultimately shaped by the trade-off between enhanced diffusion and preserved photochemical capacity.