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The chlorophyll fluorescence and leaf reflectance spectra characteristics among different ecophysiological behavior plants.
leaf reflectance spectra
photochemical reflectance index
|摘要:||為了瞭解不同生態習性植物之葉綠素螢光及葉片反射光譜特性，選用分佈於不同海拔及不同溫度適應性之植物共12種為材料，分別在中興大學 (78 m)、惠蓀林場 (800 m)及塔塔加 (2600 m)進行測定。
結果顯示不同植物其以葉綠素螢光參數所推估之光系統II (PSII)效能受低溫之影響各異，其中台灣二葉松 (Pinus taiwanensis)在低溫高光下的影響程度較兩種芒草 (Miscanthus)小，表示C4型芒草之PSII對低溫遠較分佈於同一地區之針葉樹敏感。兩種芒草之中又以低海拔原生之五節芒 (M. floridulus)受低溫影響較高海拔原生之高山芒 (M. transomrrisonensis)大。移植至惠蓀林場的兩種芒草，其光化學反射指數 (PRI) 均無差異。但在塔塔加，則以五節芒的PRI值較高山芒低，表示五節芒之PSII對低溫較敏感，需有較高的葉黃素循環消除過剩能量，以保護PSII。此外，生長於惠蓀林場平坦地及稜線上的台灣二葉松在葉綠素螢光的表現上並沒有差異，但在乾旱季節，其PRI值以生長於稜線上者較低，此差異可能與水分環境有關。
至於不同C4型植物之光合速率與所吸收光能分配之關係，顯示同一物種在不同光度下，其光合速率與電子傳遞鏈 (ETR)大多呈直線正相關。其相關係數以光合速率較高之物種較高，而光合速率最低之芒草則其相關不顯著。將五種C4型植物合併分析時發現，在低光度下，光合速率較高之葉片，其所吸收的光能用於光合作用之能量比例 (P)較高，隨光度增強此比例會逐漸變小，而且不同光合能力葉片間之P差距亦降低，至2000 μmol m-2 s-1 則P已無差異。而用於非光化學消散比例 (D)則以光合速率較低者較高，亦隨光度增加而升高。過剩能量 (E)則維持一定的比例。
從十一到二月，每日最低溫範圍從11.6 oC到22.4oC，芒果 (Mangifera indica, cv. Aiwen)及竹柏 (Podocarpus nagi)的黎明最大光化學潛能 (Fv/Fm)隨溫度下降而降低，又以芒果受影響之程度較大，而赤楊 (Alnus formosana)的黎明Fv/Fm則不受影響。五種植物合併分析時，其黎明Fv/Fm與黎明PRI值 (PRIP)間呈極顯著的曲線相關，因此，PRIP可做為PSII效能季節性變化的指標。在中午測得之實際光化學效能 (Φ)及Fv/Fm與中午之PRI值(PRIn)之間亦呈顯著之曲線相關，但與∆PRI (PRIP - PRIn)之相關性更高。而非光化學消散 (NPQ)與PRIn間之相關不顯著，但與∆PRI則呈顯著之相關。顯示對於不同溫度忍受性的物種而言，在不同季節，各種溫度及光照下，∆PRI是推估光照下PSII過剩能量實際消散的良好指標。
In order to understand the chlorophyll fluorescence and leaf reflectance spectral characteristics among species, 12 species with different elevation distribution and temperature adaptation were used. The experiments were made in the campus of National Chung Hsing University (78 m), Hui-Sun Forest Station (800 m), and Tatachia area (2600 m). The results indicated that the PSII efficiency estimated from chlorophyll fluorescence parameters of Pinus taiwanensis (conifer) was lesser influenced by the low temperature and high illumination than those of 2 Miscanthus (C4) species when they were measured in Tatachia. Among 2 Miscanthus species, low elevation origin M. floridulus was more influenced by low temperature than that of high elevation origin M. transomrrisonensis. In Tatachia, transplanted M. floridulus showed lower photochemical reflectance index (PRI) calculated from leaf reflectance spectra in the winter, indicating it required higher xanthophyll cycle to dissipate more excess absorbed energy due to PSII efficiency were more inhibited by low temperature. It also found that no difference of potential of PSII efficiency (Fv/Fm) between flatland and crest line grew P. taiwanensis in Hui-Sun Forest Station. However the PRI of crest line grew P. taiwanensis was lower than that of flatland grown in dry season, probably due to the difference of water condition between 2 habitats. It showed positive correlation between photosynthesis capacity (Pn) and electron transport rate (ETR) for C4 species. This regression coefficient was higher in the species with higher photosynthetic capacity, and no significant correlation could be found in Miscanthus, which showed the lowest Pn among 5 tested C4 species. When merged together of 5 C4 species to statistic analysis, the leaf with higher photosynthetic capacity showed higher portion of absorbed light energy for photochemical (P), and low portion for non-photochemical (D) dissipations. The slope between Pn and P, as well as Pn and D were decreasing with PAR increased. However, the portion of excess energy was not influenced by PAR. From November to December, which daily minimum temperature ranging from 11.6oC to 22.4oC, predawn Fv/Fm of mango (Mangifera indica, cv. Aiwen) and Podocarpus nagi decrease with low temperature, and mango was more influenced than P. nagi. On the contrary, predawn Fv/Fm of Taiwan alder (Alnus formosana) was lesser influenced by temperature. Nevertheless, predawn Fv/Fm showed a strong significant correlation with predawn PRI (PRIp) for statistical analysis when merged together of 3 species. Therefore PRIp could be used as an indicator to estimate the seasonal variation of the potential photochemical efficiency of PSII. Both Fv/Fm and Ф (actual PSII efficiency) showed significant curvilinear correlation with PRI (PRIn) when 3 species were merged together for statistical analysis which data measured at noon. However, more strong correlation between Fv/Fm and ΔPRI (PRIp - PRIn) as well as between Ф and ΔPRI were found. In addition, non photochemical quenching (NPQ) did not correlated with PRIn, but significant correlated with ΔPRI. Thus ΔPRI is suit to indicate the actual dissipation of the excess energy as well as PSII efficiency during illumination. As a conclusion, both chlorophyll fluorescence parameters and leaf reflectance spectra indexes are powerful tools for ecophysiological study.
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