Are pollen multicellular?
The pollen grain is an extremely simple multicellular structure. The outer wall of the pollen grain, the exine, is composed of resistant material provided by both the tapetum (sporophyte generation) and the microspore (gametophyte generation).
What is the exine made of?
While the exine is composed of sporopollenin, a complex and highly resistant biopolymer containing fatty acids, phenylpropanoids, phenolics and carotenoids, the intine is largely composed of pectin and cellulose.
What is Micro Sporogenesis?
Microsporogenesis comprises the events which lead to the formation of the haploid unicellular microspores. During microsporogenesis the diploid sporogenous cells differentiate as microsporocytes (pollen mother cells or meiocytes) which divide by meiosis to form four haploid microspores.
What are the different types of pollen grains?
On the basis of aperture types pollen grains of most families are grouped under three distinct types, namely colporate, colpate and porate. On the other hand, pollen grains of some families e.g. Cyperaceae, Juncaceae, Potamogetonaceae and Ruppiaceae are inaperturate.
What is the difference between pollen and pollen grain?
Each pollen grain is typically a single cell. They are the male gametes or sperm cells of plants. “Pollen” simply refers to a quantity of pollen grains.
Do gymnosperms self pollinate?
Sexual Reproduction in Gymnosperms Because the pollen is shed and blown by the wind, this arrangement makes it difficult for a gymnosperm to self-pollinate.
What is exine in pollen?
Exine is the outer covering of pollen grain which is highly sculptured with sporopollenin; a chemically inert polymer of carotenoid ester which is highly resistant to degradation by any enzyme, as known so far.
Where is the exine located?
Exine is commonly divided into the outer sculptured sexine and the sim- pler inner nexine, located just above the intine (Figure 2a,d).
Are pollen grains microspores?
The main difference between microspore and pollen grain is that the microspore is a small spore in land plants, which develops into the male gametophyte whereas the pollen grain is a fine granule in seed plants, consisting of a reduced male gametophyte.
What is pollen allergy called?
Pollen is one of the most common triggers of seasonal allergies. Many people know pollen allergy as “hay fever.” Experts usually refer to pollen allergy as “seasonal allergic rhinitis.”
What are pollen grains 6?
Pollen grains are microscopic structures, which bear androecium – a male reproductive organ of a flower. The interior section of pollen grain contains cytoplasm along with the tube cell, which converts into a pollen tube and the generative cell releases the sperm nuclei.
