Cytological Characteristics Of Camellia Oleifera Anther Petalized Abortion

Camellia oleifera is an important species in the Camellia genus(Theaceae).It belongs to shrubs or small arbor and is mainly distributed in the mountainous and hilly areas of southern China.Because it can provide high-quality edible oil for people to eat without occupying arable land,it plays an important role in poverty alleviation in the southern mountainous areas and ensuring national edible oil security.Therefore,the C.oleifera industry has received policy support and developed rapidly.However,the development of the C.oleifera industry is mainly limited by the link of resource cultivation,especially in the breeding and cultivation measures of varieties,which are mainly manifested in the late start of the breeding of local varieties and the backward cultivation technology,which makes C.oleifera appear as "a thousand flowers but one fruit" in production.The phenomenon of low fruit set rate.The male sterile plants found in the population of the nationally reviewed C.oleifera variety "Hua Shuo",which is the main product in production,can save the need for manual emasculation to speed up the breeding process of improved varieties,and can also be directly used in production to increase the probability of cross-pollination to improve the fruit set rate.However,the male sterile plants found still have problems such as unclear abortion period and method,which hinders the utilization of male sterile plants and the research on the molecular mechanism of abortion.In this regard,this study used mobile phone macro,stereoscopic microscope,scanning electron microscope and other methods to conduct morphological observation of sterile plants to clarify the period of sterile plant abortion and the type of anther abortion;paraffin sections combined with light microscopy were used to observe the structural observation was carried out from the light microscope level,and the cytological methods of petalized abortion of sterile plants were comparatively studied;using triphenyltetrazolium chloride(TTC)method,in vitro germination method and in vivo germination method,the function of pollen produced by petalized anthers of sterile plants was tested,and the pollen viability and the possibility of its application were evaluated.Through the morphological observation,structural observation and pollen function determination of petalized anthers of sterile plants,the cytological mechanism of petalized abortion of anthers was systematically studied,and the true identity of striate pollen was found in the study.These results provide a theoretical basis for the research and utilization of‘Hua Shuo’ sterile plants and C.oleifera pollen.The results of the study are as follows:(1)Anther petalization abortion of sterile plants mainly includes two types: complete petalization and half-petalizationIn the flower bud differentiation stage of sterile plants,in mid-July,after the stamens have completed the differentiation of anthers and filaments,some anthers are completely petalized and do not produce pollen,while the other part of the anthers are petalized in the upper part of the anther,while the lower part of the anther has a normal anther structure,and can produce a small amount of pollen.(2)The reason for anther petalization of sterile plants is that the normal division of sporogenous cells in the second stage is inhibitedIn this study,the whole development process of C.oleifera anthers from stamen primordia to loose powder was divided into 14 stages.When the anthers of sterile plants developed to the second stage,the spore primordial cells mainly took the ovary as the center and carried out periapical division to inhibit the periperiphery.Divide,which forms parenchyma,resulting in the flattening of the anthers without forming pollen sacs,and the flattened area of the petals having the same thickness as the petals.(3)Abnormal tapetum and callose in half-petalization anthers of sterile plants lead to the formation of pollen with low vigorHalf-petalized anthers flattened the tapetum at stages 6-7,while normal anthers had a thicker tapetum,which resulted in irregular shrinkage of pollen mother cells;at stage 10,the tapetum of Half-petalized anthers vacuole degraded,while normal anthers had a thickened tapetum.Similar phenomenon(tapetum vacuole degraded)appeared in the normal anthers at the 13 th stage,resulting in the absence of pollen content produced by the half-petalized anthers.The pollen viability was only 3.24% and 11.20% of the normal pollen viability by TTC and in vitro germination.(4)The striate pollen is actually the stomium cells responsible for anther dehiscenceThe pollens of the second form of C.oleifera(known as: striped pollens,abortion pollens,pseudo pollens,second type pollens,pseudopollen,empty pollens,false pollens)is actually the stomium cells responsible for anther dehiscence,The large vacuolar structure of the stomium cells is conducive to the rapid loss of water in fine weather when the pollinators are active,so that the anthers can dehiscence to complete the powder.The nuclei of stomium cells were distributed specifically,which may be related to the septum form,stomium cells differentiation and rapid water loss.Previous studies may have underestimated the vitality of C.oleifera pollen itself.