不同海拔高度台灣二葉松針葉構造之變異

Abstract

本研究以生長於大甲溪中橫公路沿線 ，不同海拔高度： 700 公尺、 1 , 1 00 公尺、 1 , 500 公尺、 2 , 500 公尺和 3 , 100 公尺的臺灣二葉松之針葉為材料，探討海拔變異對於針葉之外部形態、內部解剖和微細構造的影響，並測量上述各特徵以分析其相關性。 結果顯示針葉長度、氣孔開口深度、弗羅林環副細胞個數、均依海拔高度遞增而遞減，但氣孔排數與密度則依海拔高度遞增而遞增；葉緣刺狀毛茸的個數和表皮細胞大小，則不因海拔而異。針葉橫切面之厚度、高度和麵積在高海拔處較大，非維管束面積、葉肉組織之細胞間隙、維管束至葉表近軸面的距離、維管束寬／高比值、轉輸組織、厚壁細胞和射線胞篩胞等特徵均隨海拔升高而遞增。維管束的面積在中海拔處較大，而維管束跡的面積，則依海拔遞增而減少；至於葉表之角質層厚度、近軸面的厚壁細胞則與海拔高度無相關性。葉肉組織中的松脂管具 2 至 10 個，以中海拔處具較多的松脂管和松脂管面積；維管束內亦偶可發現 1 至 2 個松脂管，且愈低海拔之出現率愈大，在海拔 3 , 100 公尺之觀察查樣品中未發現。此種松脂管較葉肉組織中之松脂管小，且不具鞘細胞。本研究根據針葉橫切面、平行長軸切片和解離法之觀察，將轉輸組織分為二區：A 區轉輸組織具轉輸管胞和轉輸薄壁細胞，緊臨內皮層內側，除於海拔 700 公尺處其並不貫穿維管束，其餘海拔之 A 區轉輸組織皆成環狀，此區面積依海拔升高而增加； B 區轉輸組織則僅具轉輸管胞，位兩維管束跡和近軸面厚壁細胞間，依海拔之升高而遞減。葉肉細胞內的葉綠體和粒線體個數均明顯地依海拔升高而增加，並且粒線體的增加速率大於葉綠體，不過此兩種胞器的大小和射線篩胞內的粒腺體大小，均不隨海拔高度而異。 各項特徵測量經判別分析，均顯示臺灣二葉松的針葉確因海拔高度之變化而不同，且往往呈梯度變化，然而大甲溪流域之盛行雲霧帶（海拔 1,400 公尺－2,300 公尺），亦具有明顯之影響，故可知自低海拔（ 700 公尺）到高海拔（ 3,100 公尺）之臺灣二葉松具生態漸變群（ ecocline ）之存在。

The structural variation of needle leaves of Pinus taiwanensis Hay. naturally grown in the watershed of Tachiachi at different altitudes(700m, 1100m, 1 500m, 2500m and 3100)was studied . To elucidate the influences of altitudinal difference on the 26 characters of needle leaves, all measurements were analized by canonical discriminant analysis, general linear models test and correlation analysis. Morphometric data showed that neeedle length, the depth of stomata aperture and the number of subsidiary cells of Floring ring were descendent along the increasing altitudes. However, the rows and density of stomata were ascendent with elevation increasing. But, the spine of leaf margin and size of epidermal cell had no remarkable variation. Under the Observations of the cross sections , leaf area , thickness , width , nonvascular tissue area , the intercellular space of mesophyll ,the distance from vascular bundle to adaxial surface , the ratio of width to height of vascular bundle , area of transfusion tissue, sclereids and Strasburger cells were increasing as the elevation rising. The area of vascular bundle at middle elevation was largest , however, the area of vascular trace was decreased in accordance with the increasing altitudes. As for the thickness of cuticule had no correlation with elevations .Tran-sfusion tissue was grouped into “A” and “B” regions. “A” region was adjacent to endodermis and consisted of transfusion parenchyma and tracheids . The area of this region increased as elevation increasing and showed a ring form except at 700m altitude. “B” region consisted only transfusion tracheids was located between vascular traces and adaxial sclereids . The area of this region was descendent along the altitude elevating. In mesophyll there were 2 to 10 resin ducts. The number and area of resin ducts were the largest at middle altitude. Except the needles of 3100m altitude, every cross section of needle may exist 1 to 2 small resin ducts might be observed in “B” region of transfusion tissue. These resin ducts were lacking sheath cells. The probability of existance of this resin duct decreased with the increasing elevations. The numbers and areas of chloroplasts and mitochodria in the mesophyllous cells increased with the elevation increasing. But dimesions of these two organells and mitochodria of strasburger cell had no significant difference. Evidence obtained from canonical discriminant analysis and general linear models test suggests that all characters vary with the different altitudes and show a gradient changes along the elevations. The ecoclines of Pinus taiwanensis may exist from 700m to 3100m in elevation. However, the prevalent cloud belt of Tachiachi valley have some evident influences on the needle leaves.