香莢蘭在不同生長環境與發育階段的光合作用特性研究

Abstract

Vanilla planifolia Andrews (香莢蘭)為景天酸代謝(crassulacean acid metabolism， CAM)的攀附性蘭花，其果莢為世界上最具有價值的香料作物之一。自香莢蘭被引 進台灣以來，針對其栽培技術的研究逐漸增多，但關於其生態生理學的相關研究仍 然有限。本研究旨在測量香莢蘭在不同葉片發育階段以及不同生長季節與遮陰度 下的光合作用特性。研究中量測了香莢蘭葉片的氣體交換、葉綠素螢光、蘋果酸濃 度、phosphoenolpyruvate carboxylase (PEPCase)活性、碳穩定同位素值(δ13C)、葉片 性狀和 PEPCase 以及 PEPCase kinase 的基因表現。 結果顯示，成熟香莢蘭葉片於中午開始固定二氧化碳直到次日清晨。兩種 PEPCase 蛋白異構體的轉錄體皆不具有明顯晝夜變化，而 PEPCase 活性在白天可 能受 PEPCase kinase 調控。在幼葉(第一片葉)的發育過程，發現香莢蘭光合作用途 徑從 C3 轉變成 CAM。幼葉只在白天固定二氧化碳，顯示其為 C3 途徑。然而葉片 厚度和液胞大小顯示幼葉已具備 CAM 的特徵。關於幼葉的 CAM 相關基因調控值 得後續釐清。在桃園區農業改良場的田間實驗，不同季節的實驗結果顯示在夏季生 長的成熟葉片(第八片葉)表現較高的光合作用能力。而在夏季三種光強度的遮陰實 驗，相較於 1.7 mol photons m-2 d-1 的光強度，生長於 6.7 和 3.8 mol photons m-2 d-1 的成熟葉片具有較高的光合作用能力，而三種光條件下葉片的 Fv/Fm 無顯著差異。 本論文提供香莢蘭不同成熟度葉片、不同季節以及遮陰條件下的光合作用數據， 可作為台灣香莢蘭產業栽培應用之參考。

Vanilla planifolia Andrews is a climbing orchid with crassulacean acid metabolism (CAM), and its beans are among the most valuable spice crops in the world. Since its introduction to Taiwan, research has focused on cultivation, yet studies on its ecophysiology remain limited. This study aimed to investigate the photosynthetic characteristics of V. planifolia at different developmental stages and grown under different environmental conditions. In study thesis, gas exchange, chlorophyll fluorescence, malate concentration, phosphoenolpyruvate carboxylase (PEPCase) activity, stable carbon isotope ratios (δ13C), leaf traits, and the gene expression of PEPCase and PEPCase kinase were measured. Results showed that mature V. planifolia leaves exhibited CO2 fixation from noon, continuing until the following morning. Both the gene expression of PEPCase isoforms exhibited no daily fluctuation, while PEPCase activity may be regulated by PEPCase kinase during the daytime. During the development of young leaves, the photosynthetic transition from C3 to CAM pathway was observed. Young leaves (the 1st leaves) exhibited only diurnal CO2 fixation, indicated a predominant C3 pathway. However, leaf thickness and vacuole size revealed that young leaves possessed structural features associated with CAM. The regulation of CAM-related genes requires further investigation. In field experiments at Taoyuan District Agricultural Research and Extension Station, mature leaves (the 8th leaf) of V. planifolia grown in summer exhibited higher photosynthetic capacity compared to those in other seasons. In the shading experiments under three light intensities during summer, mature leaves grown under 6.7 and 3.8 mol photons m-2 d-1 showed higher photosynthetic capacity compared to those grown under 1.7 mol photons m-2 d-1. However, no significant differences were observed in Fv/Fm among the three light conditions. This thesis provides photosynthetic data of V. planifolia leaves at different developmental stages, across seasons, and under various shading conditions, serving as a valuable reference for the cultivation and management of V. planifolia in Taiwan.