Abstract

Pittosporaceae is exculsively native to the Old World. There is only one genus, Pittoporum, with five species and a variety in Taiwan, They are found from lowland (P. tobira, P. pentandrum and P. moluccanum), through median (P. illicioides in part) to high altitudes (P. illicioides in part, P. illicioides var. angustifolium and P. daphniphylloides). Except for the cultivated P. pentandrum which will grow into small tree, most species of Formosan Pittosporum, including the wild P. pentandrum are small or large shrubs. They are all mesomorphic but more or less tend to be xeromorphic. Carlquist (1977) introduced vulnerability and mesomorphy ratios to indicate the reflection of vessel elements under various ecological conditions. In Pittosporaceae as a whole, both the vulnerability ratios and mesomorphy ratio of Formosan Pittosporum are low. All alpine species, have low values of the ratio of palisade tissue to intercellular space; only P. daphniphylloides has a thick cuticle. Thus, the low figures of both ratios may reflect adaptation to a form of physiological drought, caused by the winter frost. For the lowland species, the thicker cuticle, the low figures for both ratios, may be an adaptation to the high tempratures, sunny weather and long period of drought in summer. The study of anatomical characters of leaves and stems for Taiwan Pittosporum indicate that plants of the same species vary in anatomical characters when they grow in different environmental conditions, while different species, growing close together or under similar environments, have similar annatomical characters.

中文摘要

海桐科僅分部於舊世界，台灣則僅產海桐屬，包括五種及一變種。分部自低海拔 (海桐、七里香及蘭嶼海桐) 經中海拔 (部分蔬果海桐) 至高海拔(蔬果海桐、細葉海桐及大葉海桐) 。其中僅栽培之七里香，可成為小喬木者，餘為或高或矮之灌木，包括野生之七里香。於生育習性上，台灣之海桐屬植物，均屬中生習性稍偏於早生習性者。 Carlquist (1977) 介紹爭執性及中生型比值以指示導管受各種生態因子所發生反應情況。就整個海桐科植物而言，台灣之海桐屬植物其爭執性比值與中生型比值均低。所有之高山種類均具有低的柵狀組織對細胞間隙之比值，但僅大葉海桐具有厚的角質層。因此，高山種類低數值的爭執性與中生型比值，主要緣於冬季高山常有凍霜之現象，因此引起植物體生理之乾旱。至於平地種類多具較厚之角質層，而此兩種比值的低數值，則起因於高溫，強光照及夏季常有長期乾旱的結果。 研究台灣產海桐屬植物葉莖解剖性質而獲得結論即同種海桐植物生於不同環境一下，解剖性質不同，而不同海桐植物生於相同環性下，具有類似解剖性質。