Plant Reproduction Test - 11

Each microspore mother produces 4 pollen grains by reduction division. Bilobed dithecious have four microsporangium.

Therefore,

50 x 4 x 4

= 800 male gametes are formed.

Pollen grain consists of hard covering of exine but their viability may lost with time. For Hybridisation pollen grains are collected and stored in liquid nitrogen below -196 degree Celsius temperature.

Inbreeding occurs in intraspecific flowers as contain same kinds of genetic materials. Outbreeding takes place between interspecific flowers having different kinds of genetic materials.

Inbreeding depression is the reduced biological fitness in a given population as a result of inbreeding, or breeding of related individuals. Continued self-pollination reduces the fertility and even productivity of the plant.
Thus, the correct answer is option A.

Large amount of fossilized pollen grain are found during excavation process of older parts due to tough covering of Sporopollenin that make the outer wall of pollen grain, exine. This substance cannot be hydrolyzed by any enzyme known.

• Embryogeny is the study of the changes that take place when an embryo develops from a zygote.
• It occurs near the embryo sac ’s micropylar end.
• The nucellus and integuments unite at the base of the ovule, or chalaza, in plants.
• It can be found on an ovule opposite the micropylar end.
• Chalaza is the pathway via which plant nutrients are delivered to the nucellus.
• Three antipodal cells form from the chalazal end of the embryo sac ’s cells.

• Stigma   - It is the  head  of the pistil.
  • It  receives pollen, which  begins the process of fertilization.
• Style   - It  the  stalk  of the pistil.
  • It is a long, slender stalk that connects the stigma and the ovary. 
  • When pollen reaches the stigma, it begins to grow a tube through the style called a pollen tube, which eventually reaches the ovary.
• Ovary   - It is the  base  of the pistil.
  • It holds the ovules for fertilization.
• Thalamus   - It  is present  near the stalk of the flower .
  • It  supplies nutrients to the flower.
  • It is a condensed axis of the flower from which all floral parts arise.

Endosperm cells are triploid as they are formed by triple fission of two polar nuclei and one male gamete. So, haploid cell will contain 8 chromosomes only. Root cells are diploid. Hence root cell will contain 16 chromosomes.

The meiocytecell are diploid so, haploid cell will contain 16 chromosomes. The endosperm cell are formed by fusion of two polar nuclei and one male gametes so, endosperm cells are triploid that will contain 16x3= 48 chromosomes.

Embryo of certain monocotyledonous seeds contain additional cotyledon besides one present in al monocots. This cotyledon represents the evolutionary stage of cotyledon formation from one to two.

The female gametophyte (embryo sac) develops from a single functional megaspore. This megaspore undergoes three successive mitotic divisions to form eight nucleate embryo sacs.

The first mitotic division in the megaspore forms two nuclei. One nucleus moves towards the micropylar end while the other nucleus moves towards the chalazal end. Then, these nuclei divide at their respective ends and re-divide to form eight nucleate stages. As a result, there are four nuclei each at both the ends i.e., at the micropylar and the chalazal end in the embryo sac. At the micropylar end, out of the four nuclei only three differentiate into two synergids and one egg cell. Together they are known as the egg apparatus. Similarly, at the chalazal end, three out of four nuclei differentiates as antipodal cells. The remaining two cells (of the micropylar and the chalazal end) move towards the centre and are known as the polar nuclei, which are situated in a large central cell. Hence, at maturity, the female gametophyte appears as a 7-celled structure, though it has 8 nucleate.

Crop improvement programme is carried out to obtain crops with desired traits that may be more yields, resistance to disease, higher nutrient value etc. Two plants having desired traits are hybridized to obtain combination of desired traits.

About Plant Reproduction :

• Sexual Reproduction  is defined as the  production of a (New organism)  from  Two-parents  by using their  (Gametes or Sex cells) .
• Plants  also have  Male and Female sex organs.
• These plants are called  (Angiosperms  or Flowering plants)  as they reproduce by the  Sexual reproduction method. 
• Most of the plants contain  Reproductive organs of both (Males  and Females) in the flowers.
• The (Male organ part)  of a flower is called the  (Stamen)  and the  (Female organ part)  of a flower is called  (Carpel).
• These  Pollen Grains  help  in making (Male Gametes)  of the plant   and are  present in Anther .
• The  (Male Gametes)  fertilize the  (Female Gametes) .
• The  fertilized  (Egg cells)  grow in Ovules   and become  Seeds .
• When  germinated , these  Seeds  started growing as  (new Plants) .

Image of the Plant Reproduction:

The number of ovule present in ovary determine the number of seeds produced inside the fruit. Mango and neem produce single seed in each fruit. Lemon contain a number of seeds but orchid contain many small size seeds.

Dormancy is the state of state of inactivity during which metabolic process slows down. Seed may remain viable to several months to years depending upon type of seeds and condition.