Que, Angiosperm के 5 लक्षण बताइए ।
Que 2, angiosperms life cycle को रेखांकित कर समझाइए।
Que 3, double fertilization किसे कहते है?
Que 4, angiosperm के आर्थिक महत्त्व
बताइए।
Answers
question1.
Angiosperms are able to grow in a variety of habitats. They can grow as trees, shrubs, bushes, herbs, and small flowering plants. Some of the characteristics of angiosperms include:
-All angiosperms have flowers at some stage in their life. The flowers serve as the reproductive organs for the plant, providing them a means of exchanging genetic information.
-Angiosperms have small pollen grains that spread genetic information from flower to flower. These grains are much smaller than the gametophytes, or reproductive cells, used by non-flowering plants. This small size allows the process of fertilization to occur quicker in the flowers of angiosperms and makes them more efficient at reproducing.
-All angiosperms have stamens. Stamens are the reproductive structures found in flowers that produce the pollen grains that carry the male genetic information.
-Angiosperms have much smaller female reproductive parts than non-flowering plants, allowing them to produce seeds more quickly.
-Angiosperms have carpels that enclose developing seeds that may turn into a fruit.
-A great advantage for angiosperms is the production of endosperm. Endosperm is a material that forms after fertilization and serves as a highly nutritional food source for the developing seed and seedling.
question 2
The Angiosperm Life Cycle
Plants have a life cycle split between two multicellular stages: a haploid stage—with cells containing one set of chromosomes—and a diploid stage—with cells containing two sets of chromosomes. The haploid stage is the gamete-producing gametophyte, and the diploid stage is the spore-producing sporophyte.
Today, most plants grow from seeds and produce flowers and fruit; such plants are called angiosperms. Angiosperms begin as seeds—structures consisting of a protective seed coat, a nutrient supply, and an embryo. The seed develops into a sporophyte—the familiar, flower-producing plant form.
The reproductive life cycle of angiosperms begins with flowering. Stamens and carpels contain sporangia, structures with spore-producing cells called sporocytes. Sporophytes produce spores as either eggs or sperm, depending on their origin.
For example, male spores—called microspores—are produced within anthers at the tips of stamens. A microspore develops into a pollen grain—the male gametophyte. A pollen grain contains a tube cell and a generative cell, which develops into sperm.
A carpel consists of an ovary and its ovules. Female spores, called megaspores, are produced within ovules. A megaspore develops into an embryo sac—the female gametophyte—which contains the egg.
Pollination allows the sperm-producing pollen grain to reach the egg-containing embryo sac. While the embryo sac is stationary, pollen grains can be carried by wind, water, or animals.
For sperm to fertilize an egg, pollen released from the anthers must reach the sticky stigma at the tip of a carpel. Then, the tube cell of the pollen grain becomes a pollen tube, extending down the carpel to the ovule.
Angiosperms undergo a type of double fertilization that produces an embryo and an endosperm, a nutrient store. The embryo and endosperm are packed into a seed coat, forming a seed. As the ovules become seeds, the ovary typically develops into fruit that helps protect and distribute the seeds.
question 3
Double fertilization is a complex fertilization mechanism of flowering plants (angiosperms). This process involves the joining of a female gametophyte (megagametophyte, also called the embryo sac) with two male gametes (sperm). It begins when a pollen grain adheres to the stigma of the carpel, the female reproductive structure of a flower. The pollen grain then takes in moisture and begins to germinate, forming a pollen tube that extends down toward the ovary through the style. The tip of the pollen tube then enters the ovary and penetrates through the micropyle opening in the ovule. The pollen tube proceeds to release the two sperm in the megagametophyte.