Study on Pollen Viability and Stigma Receptivity of Very Later-ripening ‘Dongxing' Apricot

[Objective] The primary aims of this study were to understand the characteristic of floralorgan development in ‘Dongxing＇, and analyze its differences with other apricot varieties. [Method] Floral organ morphology, pollen quantity, pollen viability and stigma receptivityof ‘Dongxing＇ and other apricot varieties were observed and measured. [Result] The ratio between the medium style and long style of‘Dongxing＇ was 82.4%, and the ratio of pistillode was lower than that in the other apricot varieties. Its pollen quantity was 32 183.2 grains per flower, and was fewer than the others. The pollen germination of ‘Dongxing＇ in optimum medium（1% agar ＋15% sucrose ＋ 0.01% boric acid） was 53.0%, i.e. its pollen viability was low. The pollen viability increased at first and then decreased following the period of the bud stage to flowering stage, and pollen viability reached maximum value at the 1st d after flowering. Meanwhile the stored pollen viability continuously decreased with the extension of storage time, and pollen viability of the both vivo or vitro stored was decreased to the half of the maximum value at the 3rdd after flowering or storage.The stigma receptivity of ‘ongxing＇ enhanced at first then weakened, maximum stigma receptivity was found at the period of 2 h to 4 h after flowering. The optimum time for artificial pollination was 1 h to 8 h after flowering and it was shorter than the other apricot varieties was. [Conclusion] The ratio between the medium style and long style of ‘Dongxing＇ was higher than the other apricot varieties, while the pollen viability of ‘Dongxing＇ on the contrary. Its pollen viability reached maximum value at the 1st d after flowering and the optimum time for artificial pollination was1 h to 8h after flowering.

Observation of Flowering Process of Grape(Vitis vinifera L.)—Insight into the Starting of Pollination of Flower Hiding in Calyptras(Cap)

It is generally agreed that many Vitis vinifera L.cultivars are self-fertile,where self-pollination often occurs before capfall in a process called cleistogamy.Therefore,it is difficult to identify the right time to remove stamens before self-pollination during the cross-breeding of grape.For this paper,we observed the process of grape flowering and measured the pollen viability and stigma receptivity of grape flowers of‘Shine Muscat’in order to identify the starting time of self-pollination before capfall and to provide useful information for improving the efficiency of cross-breeding.The results demonstrate that the anther is not cracked during the visible clusters and separated clusters stages.Meanwhile,in the separated floral buds,flowering begins,and full bloom stages,the pollen viability is 60.7%,73.2%and 80.3%,respectively;however,at the berry set stage,pollen viability drops to zero.The top of the mature stigma is composed of a layer of nearly cylindrical papillary cells,and the stigma receptivity for pollen changes with the development of flowers:in particular,no reaction was observed in the visible clusters stage;weak positive reaction at the separated clusters stage;strong positive reaction at the separated floral buds,flowering begins,and full bloom stages;and no reaction at the berry set stage.In the separated floral buds stage,pollen tubes were seen germinating in the style.In the flowering begins stage,more pollen tubes were observed at the entry of the ovary.During the full bloom stage,most pollen tubes elongated into the ovary base and some entered the pearl hole.At the berry set stage,newborn endosperm nucleus could be seen in the ovule.From the above,we can conclude that the initiation time of closed fertilization for‘Shine Muscat’grape can be judged as the separated floral buds stage,and it is best to discard the stamen before the separated floral buds stage when conducting cross-breeding.

Study on the Flowering Biological Characteristics of Prunus domestica × armeniaca

[Objective] The aims of this study were to understand the flowering biological characteristics of Prunus domestica ×armeniaca and analyze its differences with other apricot varieties and plum varieties. [Method] Taking three varieties of Prunus domestica ×armeniaca as the research object, the phenophase of blooming,morphology characteristics of floral organs and development characteristics of floral organs were observed, pollen amount, pollen viability and stigma receptivity were measured. [Result] The results showed that three varieties of Prunus domestica×armeniaca were in blossom in early April, the florescence were relatively late for 8-12 d comparing with the varieties of apricot, the florescence were relatively similar to the P. domestica L. Morphology characteristics of floral organs of three varieties of Prunus domestica×armeniaca had few differences, were relatively similar to two varieties of plum, and they all had high percent of middle-style and long-style flower.The pollen amount of three varieties of Prunus domestica ×armeniaca had a little differences comparing with two varieties of plum, but were lower than three varieties of apricot. There were some differences in pollen viability, the germination percentage of pollen of ‘Konglongdan＇ was relatively high, was 51.6%; The pollen amount of ‘Fengweihuanghou＇ was relatively high, was 880.8 per anther; ‘Weidi＇ had fewer pollen amount, and the pollen viability was just 2.1%; Three varieties of Prunus domestica ×armeniaca all had strong stigma receptivity on the bloom day, and the stigma receptivity continued exist until the day that 5 days after blooming. [Conclusion] The florescence of three varieties of Prunus domestica ×armeniaca were relatively concentrated, and the rate of pistil abortion was lowest, the variation intensity of stigma receptivity and sustainable time of three varieties of Prunus domestica×armeniaca almost had a little differences comparing with a variety of plum, but slightly more than three varieties of apricot.

The Flowering Biology of Plum(Prunus domestica L.) in Aksu Region, Xinjiang

[Objective] The aim of this study was to understand the flowering biological characteristics of different varieties Prunus domestica L. in Aksu Jiamu Experi- ment Station. [Method] Three varieties of plum as Prunus domestica L. cv. ＇French＇, Prunus domestica L. cv. ＂Victoria＇ and Prunus domestica L. cv. ＂Stanley＇ were the research subjects. The phenophases of blooming, and the morphological and developmental characteristics of floral organs were observed. The amount and viability of pollen and the stigma receptivity were measured. [Result] Three varieties of plum all blossomed in early April, and the florescence had lasted for 9-10 d. The average number of anthers was 28.48%. The average number of pollen grains in each flower was 28 700.0. The pollen germination rate was 27.4%. 86.75% of the flowers were medium-styled or long-styled. There was no significant difference in the petal shape, color, anther number, calyx color, and flower ovary among the three varieties of plum. The stigma receptivity was strongest on the first day of flowering, and then dropped gradually. Therefore, the flowers of plum were manual pollinated on the first day of flowering. The duration time of stigma receptivity of Prunus domestica L. cv. ＇Victoria＇ was longer than the other cultivars, the duration time of stigma receptivity was about 5 d. [Conclusion] The pollen number and pollen germination rate of Prunus domestica L. cv. ＇Stanley＇ were higher than the other cultivars, which be considered the most suitable pollinizer for plum. In contrast, the complete flower rate of Prunus domestica L. cv. ＇French＇ and Prunus domestica L. cv. ＇Victoria＇ was relatively high, but the pollen number and pollen germination rate of Prunus domestica L. cv. ＇French＇ and Prunus domestica L. cv. ＇Victoria＇ were lower than Prunus domestica L. cv. ＇Stanley＇, which are not suitable to use as a pollinizer for plum.

Effects of Dust on Male and Female Floral Organs and the Pollination of the Walnut

The Tarim Basin,Xinjiang,China,a region important to the walnut industry,is affected by frequent heavy dust storms.Dust,including micro-particles(diameter<10μm),covers the surface of the walnut tree,thereby changing the surface-atmosphere interface microenvironment,which,in turn,influences the exterior and interior structure of the tree.Dust storms occur in spring and summer,during the flowering period of walnut,which is the key developmental stage leading to fruit formation.This study investigated the effects of dust on female flowers,male flowers,and the pollination of walnut.The morphological changes in the stigma during pollination were recorded.Stigma receptivity was studied via the benzidine–H2O2 method.Morphological features of the female floral organs and pollen were investigated using scanning electron microscopy.Pollen germination and pollen tube growth were examined by fluorescence microscopy.The results showed that dust had a significant inhibitory effect on male and female flowers,resulting in decreased catkin growth,reduced pollen viability(pollen viability was 20.13%),blocked pollen apertures,a reduced pollen germination rate on the stigma,and increased time needed for pollen tube appearance.Dust also had an inhibitory effect on stigma length and receptivity of female walnut flowers,with the length of the walnut stigma being reduced by 0.25~0.80 mm during the flowering process.In addition,there was decreased stigma mucus,resulting in stigma atrophy,decreased amount of pollen on the stigma,weakened stigma receptivity,and accelerated drying of female flowers.In the Tarim Basin,walnut flowering occurd at the same time as dust storms do,which had a negative impact on the floral organ,flowering and pollination of walnut.

Stigma Receptivity Is Controlled by Functionally Redundant MAPK Pathway Components in Arabidopsis

In angiosperms,the process of pollination relies on species-specific interaction and signaling between the male(pollen)and female(pistil)counterparts where the interplay between several pollen and stigma proteins decides the fate of the pollen.In Brassicaceae,the dry stigmatic papillary cells control pollen germination by releasing resources only to compatible pollen thereby allowing pollen to hydrate and germinate.Despite the identification of a number of stigmatic proteins that facilitate pollination responses,the signaling mechanisms that regulate functions of these proteins have remained unknown.Here,we show that,in Arabidopsis,an extremely functionally redundant mitogen-activated protein kinase(MAPK)cascade is required for maintaining stigma receptivity to accept compatible pollen.Our genetic analyses demonstrate that in stigmas,five MAPK kinases(MKKs),MKK1/2/3/7/9 are required to transmit upstream signals to two MPKs,MPK3/4,to mediate compatible pollination.Compromised functions of these five MKKs in the quintuple mutant(mkk1/2/3RNAi/mkk7/9)phenocopied pollination defects observed in the m pk4RNAi/m pk3 double mutant.We further show that this MAPK nexus converges on Exo70A1,a previously identified stigma receptivity factor essential for pollination.Given that pollination is the crucial initial step during plant reproduction,understanding the mechanisms that govern successful pollination could lead to development of strategies to improve crop yield.