北美紅杉表皮特微分析

Epidermal Structures of Sequoia sempervirens (D. Don) Endl. (Taxodiaceae)

北美紅杉（Sequoia sempervirens(D. Don) Endl.）是紅杉屬現在僅存的一種植物。有關北美紅杉表皮特徵的報導存在分歧。本文觀察包括原產地及不同產地的北美紅杉的完整葉片的表皮特徵。結果顯示其葉片上下表皮細胞特徵相似，但存在於氣孔區與非氣孔區的表皮細胞形態與大小不同。不同葉片的氣孔數量和分佈在下表皮變化不明顯，在上表皮變化較大。根據氣孔在上表皮的分佈特點，將氣孔分布情況分為四種。氣孔保衛細胞下陷，副衛細胞覆蓋部分保衛細胞，副衛細胞數目4-6個，但多數為4個，偶有超過6個。氣孔口長軸多數與中脈平行，也存在氣孔口長軸與中脈垂直或斜向的情況。

Sequoia sempervirens (D. Don) Endl. is the unique living species of genus Sequoia. Epidermal structures of S. sempervirens were reported divergently. This study focuses on the understanding of variation of the epidermis structures of S. sempervirens, based on integral leaves, rather than on leaf fragments. Epidermal cells on both upper and lower surfaces of leaves possess similar features, but their shape and size in non-stomatal areas are different from those in stomatal areas. The amount and distribution of stomata on the lower surface vary indistinctly, but obvious variations of them on the upper surface are described as four situations. Guard cells of stomata are sunken and partly blanketed with subsidiary cells. Each stoma has 4-6, but mostly 4 subsidiary cells, occasionally exceeding 6. Long axes of stomata are mostly parallel to, but sometimes oblique or perpendicular to the mid-vein.