Are pollen and spores homologous?
The spores of ‘lower’ spore-bearing plants and the pollen of ‘higher’ seed plants are homologous. This suggests that the molecular genetics of spore/pollen development are highly conserved, despite the large morphological and functional differences between spores and pollen.
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 a mature pollen grain?
Mature pollen grains are suboblate to spheroidal, isopolar, radially symmetrical and 3-porate. However, before being shed from the anthers, large numbers of starch grains become visible inside the pollen grains, as well as in the cytoplasm towards the distal end of the epidermal cells of the pollen presenter.
Where is a mature pollen grain produced?
anther sacs
Pollen grains are produced by meiosis of microspore mother cells that are located along the inner edge of the anther sacs (microsporangia). The outer part of the pollen is the exine, which is composed of a complex polysaccharide, sporopollenin.
What is the difference between spores and pollen?
Spore is a haploid cell derived from sporangium via meiosis, whereas pollen is an immature, endosporic male gametophyte derived from male spores (microspores) in seed plants.
What does a sporangium do?
A sporangium is a structure in certain plants and other organisms that is charged with making and storing spores. Spores are haploid structures created in organisms that help to germinate and form new organisms. In other words, they help organisms to reproduce.
What are pollen grains 10?
What are Pollen Grains? 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.
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.”
Is Intine continuous?
1) Intine or inside layer is a thin and continuous layer made of cellulose or hemicellulose and pectin.
What is Intine made up of?
cellulose
The intine, or inner layer, consists primarily of cellulose and pectins. The exine, or outer layer, is composed of a highly decay-resistant chemical called sporopollenin.
How do Microspores form pollen grains?
During microspore mitosis, the pollen first develops a large vacuole that mediates nuclear migration to produce polarized cells. Concomitantly, starch begins to accumulate and the vacuolar volume decreases in the maturing pollen. Once fully mature, pollen grains are released from the dehiscent anther for dispersal.
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.
What kind of substance are pollen grains made of?
Pollen is a fine to coarse powdery substance comprising pollen grains which are male microgametophytes of seed plants, which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametophytes during the process of their movement from the stamens to the pistil…
What kind of pollen has a furrow across the middle?
Sulcate pollen has a furrow across the middle of what was the outer face when the pollen grain was in its tetrad. If the pollen has only a single sulcus, it is described as monosulcate, has two sulci, as bisulcate, or more, as polysulcate. Colpate pollen has furrows other than across the middle of the outer faces.
How are pollen grains preserved in the fossil record?
The callose wall is broken down by an enzyme called callase and the freed pollen grains grow in size and develop their characteristic shape and form a resistant outer wall called the exine and an inner wall called the intine. The exine is what is preserved in the fossil record.
What is the name of the nasal allergy to pollen?
Nasal allergy to pollen is called pollinosis, and allergy specifically to grass pollen is called hay fever.