向日葵叶片动态及功能叶的研究

本文研究了向日葵叶生长动态及功能叶。最初8叶对生,其余轮生。现蕾前叶从茎底部向顶端依次已全部长出,现蕾后到开花阶段则全部展开、扩大,开花期最大叶面积可达1.4m以上。植株呈两头小中间大株型。开花前底部叶片开始黄落,灌浆阶段仅余69％的叶片。生长过程上部邻近的展开叶给新生叶及花盘提供光合产物。主要功能叶层,在花序及开花阶段为植株中部偏上的第19—30叶、灌浆阶段为靠近花盘的第31—39叶,这些叶片的光合强度较大,平均3g/m~2/小时,距花盘越远的叶片功能越小。

A STUDY ON LEAF DYNAMICS AND FUNCTIONAL LEAVES OF SUNFLOWER

Leavies of sunflower are the main organ of assimilation.In this paper leaf dynamics and functional leaves of "Hybrid BC-H-1 " were obseved. The "Hybrid BC-H-1 " had 39 leaves, four pairs blades at bottom were opposite, and the others were whorled.Before budding stage, leaves were all grown out from bottom to top strata on a stem, and expanded its area three times in budding to flowering stage, and reached its climax of above 1.4m2 in full blooming stage.The bottom and top leaves in area size were smallest increasing towards the mid-height of stem.The area of medium leaves was 32 times larger than the area of the bottom leaves.But about one week before flowring, leaves at bottom begin to die. off and reduced the leaf number.Therefore only half of total leaves. left in filling per-iod.In grow'ing period, the developed leaves provided photosynthates to the developing new leaves or head which were near by as the growing center of a stand.The main functional leaves were No 91-30 blades at mid-height of stem, in formation period of head and blooming stage, and No 31-39 leaves in filling period.In this stage, the leaf was smaller, but had a relatively high net assimilation rate of 3g.m-2 leaf area hour-1 leaves, which were far depart from the head, had the least important function.