台湾芒草之光合作用特性

The Photosynthetic Ckaracteristics of Miscanthus Species in Taiwan,

芒草为Ｃ＿４型植物，叶片上表皮气孔数目很少，高山所产者尤甚，而且产于高山的芒草，其叶片上表皮覆盖一层可能是角质层的物质，不容易分辨表皮细胞，而产于低海拔者则否。其ＣＯ＿２补偿点，除了高山芒接近９ｐｐｍ之外，其余在３．５～６．５ｐｐｉｎ。光合成率对光度之反应呈饱和曲线。在未施氮区，芒草单叶之饱和点为７５０～１２５０μＥ／ｍ￣２／ｓ，其最大光合成率（Ｐｎ介于８－１６μｍｏｌＣＯ＿２／ｍ￣２／ｓ之间，每盆施氮２ｇ，１０天后其最大光合成率增为１２～２０μｍｏｌＣＯ＿２／ｓ，光饱和点则为１０００～１５００μＥ／ｍ￣２／ｓ。此值较一般Ｃ＿４型植物为低，而接近Ｃ＿３型作物。唯无论未施氮区或施氮区，光合成率以产于南部（包括兰屿及垦丁）之营养系较高，产于北部者次之，产于山区者较低。将所有供试材料在各种氮肥处理下所得结果合并分析时，最大光合成率与叶片之叶绿素含量、叶片导度、叶肉导度及光饱和点间呈正相关。光合成率与叶温间之关系随营养系及季节而异，当温度从１７℃升至３７℃（气温约为１５～３５℃）时，部分在平地及海拔１０００ｍ左右所采集之营养系，其光合成率随温度直线上升，其余营养系则呈曲线关系。其中，在三义及玉井各有１营养系，其光合?

AbstractMiscanthus spp. is the most widely distributed and important native grass in Taiwan. It is a C_4 grass from lowland to high mountainous areas of about 3000m in elevation. The maximum net photosynthesis of leaf(Pn)in non-nititrogen treatment were 8～16μmol Co_2/m￣2/s and light saturation point were 750～1250 μE/m￣2/s, while the Pn of Miscanthus in the nitrogen treatment (2g N/pot)were 12～20 μmol CO_2/m￣2/s,light saturation point were 1000～1500 μE/m￣2/s.The Pn of some clones collected from low-land and hillside mountainous areas increased linearly when leaf temperature increased from 17 to 37℃ showed quadratic relationship with leaf temperature,some clones fromhigher mountains wrer saturated with or decreased in Pn above 30℃,As compared tothe clones from hillside mountainous areas, the Pn of clones from lowland and highermountain decreased at a lower rate when leaf temperature decreased from 30 to 20℃.The Pn of mountainous clones was acclimated partilly to temperatue in different sea-sons.It was also acclimated when cultivated for a long time in lowland. The Pn was in-hibited when leaf water potential(L)was below-1.3 to-1.5 MPa and the L val-ues in 50%Pn was decreased when L values were-1.6 to-2.6 MPa. The L val-ues became lowet to inhibit 50% Pn in all the tested clones when more drying cycles were applied.The clonal differences of the tolerance and acclimation of photosynthesis in water deficits was closely related to the osmotic adiustment. The clonal difference of the osmotic adjustment could reflect the pattern of rainfall of collected region.