Developments Of Female And Male Gametophytes In Sassafras Tzumu

As an important timber,Sassafras tzumu grow seedlings difficultly because of low seed-setting rates.Much has been learned about the anatomy,domestication and reproduction of Sassafras tzumu,yet the available data are still far from being distinct and complete.In this dissertation,By means of paraffin section,electron microscope scanning(EMS)and I2-KI testing,we have investigated the developmental process of some key organs or tissues,such as megaspore,microspore,male gametophyte and female gametophyte.The main results are as follows:1.The flower of Sassafras tzumu is bisexual and bright yellow with 12 stamens(9 fertile stamens and 3 sterile stamens),a single ovary with 1 ovule(or two ovaries rarely).2.Anther walls of Sassafras tzumu are the basic type,including epidermis,endothecium,middle layer and deformed tapetum from the outside,respectively.3.Some microspore cannot normally develop,showing aberrant forms like"crescent-shaped","T-shaped" or "bone-shaped",or cavities pollen.And in the perfected anthers,there has been a lot of condensed pollens before anther sac is not opened.4.Megasporogenesis of Sassafras tzumu is normal and polygonum-type;but parts of embryo sacs are aborted,resulted from degradated nucleuses and cytoplasm.5.There are three days overlaped between the epoch of pollen viability and the period of stigma acceptable pollination.Pollen stored at-29? can persist significantly longer than that at-4?or room temperature,so that it can be used to hand-pollinate.In a word,these consequences not only have elucidated the developmental mechanisms underlying the low seed-setting rates,but also will facilitates the breakthroughs in the cultivation of Sassafras tzumu.