Small non-coding RNAs are essential for development of the sporophyte, the somatic diploid phase of flowering plants. They are integral to key cellular processes such as defense, generation of chromatin structure, and regulation of native gene expression. Surprisingly, very little is known of their presence and function in the male haploid phase of plant development (male gametophyte/pollen gra...

Pectin is a complex polysaccharide and an integral part of the primary plant cell wall and middle lamella, contributing to cell wall mechanical strength and cell adhesion. To understand the structure-function relationships of pectin in the cell wall, a set of transgenic potato lines with altered pectin composition was analysed. The expression of genes encoding enzymes involved in pectin acetyla...

The genus Brachiaria contains species that have great economic importance in the Brazilian agricultural sector, as they enable cattle ranching on acid and poor soils with species that are resistant to spittlebugs and form crop-livestock-forest integration systems. The genus mainly consists of tetraploid (2n = 4x = 36) and apomictic species such as B. decumbens and B. brizantha. Sexuality is fou...

in vitro pollen germination and also pollen tube growth dynamics in different pollination treatments under controlled temperature, humidity and photoperiodicity were studied regarding four cultivars (‘shastomi - e - do’, ‘ebrahim - e - kalajah’, ‘sefid - e - rezaeeieh’ and ‘razi’) under self and under cross-pollination along with three superior genotypes (‘269’, ‘416’ and ‘464’) of apricot. fol...

A polarized division occurs normally in the development of microspores in plants. The result is a presumptive vegetative cell and generative cell within the young pollen grain. The generative nucleus in Tradescantia synthesizes DNA and considerably later, in the pollen tube, it divides to form two sperm nuclei. The vegetative nucleus probably degenerates in the pollen tube. In Tradescantia, it ...

BACKGROUND AND AIMS Pollen grains of 37 species from 11 genera in the family Zingiberaceae were examined to assess qualitatively starch or lipid contents; the pollen grain and ovule numbers per flower and pollen : ovule ratios were also counted and calculated. Pollen : ovule ratios were studied to reveal patterns of variation in the Zingiberaceae. METHODS Freshly open flowers with dehiscing a...

During male meiosis in wild-type Arabidopsis the pollen mother cell (PMC) undergoes two meiotic nuclear divisions in the absence of cell division. Only after telophase II is a wall formed which partitions the PMC into four microspores. Each microspore undergoes two subsequent mitotic divisions to produce one vegetative cell and two sperm cells in the mature pollen grain. In this paper we descri...

Speciation involves the formation of reproductive isolating mechanisms such as a difference in pollinators, incompatibility between pollen tubes and stylar tissue, hybrid seed abortion, or poor growth of hybrid seedlings. We studied reproductive isolating mechanisms in naturally sympatric populations of Penstemon spectabilis Thurber and Penstemon centranthifolius (Benth.) Benth. where F1 hybrid...

During pollen development each product of meiosis undergoes a stereotypical pattern of cell divisions to give rise to a three-celled gametophyte, the pollen grain. First an asymmetric mitosis generates a larger vegetative cell and a smaller generative cell, then the generative cell undergoes a second mitosis to give rise to two sperm cells. It is unknown how this pattern of cell divisions is co...

In a previous review of male gametophyte development (McCormick, 1993), it was noted that the two areas posed by Mascarenhas (1975) as fruitful areas for future research were the following. What are the differences in the two cytoplasms that determine the different cell fates of the generative and vegetative cells? And what are the functions of pollen-specific proteins? Now, 10 years later, the...