Introduction to angiosperms - class-XI

In angiosperms, the functional megaspore (usually the chalazal one) undergoes three successive rounds of free-nuclear mitotic divisions to form an 8-nucleate, 7-celled embryo sac. Therefore, it undergoes mitosis thrice.

Cotyledons are the leaves of embryo. Their number is either one or two. Sometimes, they store food materials and become fleshy.

• Monocot plants seeds have one cotyledon. Rice, wheat, maize, bamboo, palm, banana, ginger, onion, garlic, lilies, daffodils, iris, orchids, bluebells, tulips, amaryllis are examples of monocots.

Angiosperms are also called as flowering plants. Monocots contain a single cotyledon as because the endosperm needed to nourish is not present outside the seed leaf. Therefore, the correct answer is option A.

Sunflower is a dicot plant meaning that it produces two cotyledons. Dicots produce two leaves when they first germinate. The leaves of a dicot vary in shape and size, with the veins extending out from the center. Roots of a dicot are tough and branched. A sunflower seed is a dicot that contains the characteristic double cotyledon. The cotyledon, also known as a seed leaf, holds food reserves for the developing seed. Sunflower is a flowering plant and not a monocot or pteridophyte.

Angiosperms are the flowering plants. Their seeds develop inside a female reproductive part of the flower, called as the ovary, which usually ripens into a protective fruit. Gymnosperms do not have flowers or ovaries. Their seeds mature inside cones. Seeds may be carried away from the parent plant by wind, water, or animals. Mango is an angiosperm. Cycas, Ginkgo and Pinus are gymnosperms. 

Thallophyta and bryophyta are cryptogams. They do not have vascular tissue and reproductive tissue, they are non-vascular plants and they reproduce asexually by formation of spores. They are flowering plants and have vascular and reproductive tissue.

Angiosperms are also called as flowering plants. They are classified based on characteristics that include cotyledon structure, pollen grains, as well as flower and vascular tissue arrangement. Basal angiosperms, classified separately, contain features found in both monocots and dicots, as they are believed to have originated before the separation of these two main groups. Monocots contain a single cotyledon and have veins that run parallel to the length of their leaves; their flowers are arranged in three to six-fold symmetry. Dicots have flowers arranged in whorls, two cotyledons, and a vein arrangement that forms networks within their leaves. 

Angiosperms are also called as flowering plants that are classified based on characteristics that include cotyledon structure, pollen grains, as well as flower and vascular tissue arrangement. Basal angiosperms, classified separately, contain features found in both monocots and dicots, as they are believed to have originated before the separation of these two main groups. Monocots contain a single cotyledon and have veins that run parallel to the length of their leaves; their flowers are arranged in three to six-fold symmetry. Dicots have flowers arranged in whorls, two cotyledons, and a vein arrangement that forms networks within their leaves. 

Angiosperm are subdivided into two classes which are cotyledons and dicotyledons depending on the number of cotyledons in their embryo. Maize has just one cotyledon in its embryo.

Phanerogamae are the sub-kingdom of kingdom Plantae. They include seed bearing and flowering plants. They are further grouped into angiosperms and gymnosperms. Angiosperms are subdivided into two classes which are cotyledons and dicotyledons depending on the number of cotyledons in their embryo.

Angiosperms are flowering plants and are not cryptogams (which are non-flowering plants like algae, mosses, and ferns). They have seeds enclosed in fruits, possess vessel elements, and have companion cells.

The endosperm in angiosperms is triploid (3n). If 3n = 24, then n = 8. Gametes are haploid (n), so they contain 8 chromosomes.

Meiosis produces pollen grain. Its cell divides mitotically to form generative nucleus and tube cell. The generative nucleus undergoes another mitosis to form two male gametes.

The microspore nucleus undergoes one mitotic division to form the vegetative and generative cells. The generative cell then undergoes a second mitotic division to produce two male gametes. Thus, two mitotic divisions occur.

The standard sequence in the angiosperm life cycle is pollination, followed by fertilization, which leads to seed formation, and finally germination of the seed.

Microsporogenesis involves the formation of microspores from a microspore mother cell via meiosis, which results in four equal-sized haploid microspores. The other options involve unequal divisions (e.g., generative cell formation, zygote division).

In the development of the proembryo, the zygote (oospore) divides to form a terminal cell and a basal cell. The basal cell gives rise to the suspensor, while the terminal cell gives rise to the embryo proper.

Agamospermy (apomixis) in various plants, including apple, can be induced or promoted by the application of specific plant growth hormones.

Endosperm is formed by the fusion of one male gamete (n) and two polar nuclei (n+n). The female plant is 2n=24, so n=12. The male plant is 2n=12, so n=6. Endosperm = (n from male) + (n from female) + (n from female) = 6 + 12 + 12 = 30.

Both microsporogenesis (in anthers) and megasporogenesis (in ovules) involve meiotic divisions to reduce the chromosome number from diploid to haploid.

The secondary nucleus (formed by fusion of two polar nuclei) is diploid (2n), and the endosperm (formed by fusion of a male gamete and secondary nucleus) is triploid (3n).

The Anthostrobilus theory, proposed by Arber and Parkin, suggests that angiosperms evolved from an extinct group of gymnosperms called Caytoniales (often spelled Caytoniales).

All three statements are correct: hydration triggers enzymatic activity, which increases respiration, and this high metabolic rate persists until the seedling is established (senescence of the seed stage).

According to Hutchinson's classification system for angiosperms, primitive flowers are characterized by a spiral arrangement of floral parts on an elongated receptacle or torus (acyclic or hemicyclic arrangement), numerous stamens, and an apocarpous superior ovary with actinomorphic corolla. Thus, characteristics 1, 3, and 4 define primitive flowers.

In angiosperms, one microspore mother cell undergo meiosis, form into four microspores or pollen grains. Each pollen grain by undergoing two mitotic divisions produces two male gametes. 63 microspore mother cells undergo 63 meiotic divisions and form into 252 microspores or pollen grains. These microspores undergo 500 mitotic divisions and form into 500 male gametes.

So, the correct option is ’63
and 500’. 

When the male nucleus fertilizes the egg cell, the entire ovule is converted into a structure which is known as a seed. The endosperm which is formed after double fertilization or triple fusion nourishes this growing seed.

Each microspore mother cell (MMC) undergoes one meiosis to produce 4 pollen grains. To get 250 pollen grains, we need 250/4 = 62.5 MMCs. Since we cannot have half a division, we need 63 meiotic divisions (62*4 = 248, plus one more division to get the remaining 2).

Sinigrin is a glucosinolate that belongs to the family of glucosides found in some plants of the Brassicaceae family such as Brussels sprouts, broccoli etc. Carthamin is a natural red pigment obtained from safflower oilseed crops belongs to the family Asteraceae. Atropine and vasopressors act to combat bradycardia and hypotension and are derived from the plants that belong to the family Liliaceae.  Aloe vera produces secondary metabolites, such as aloin, which is used in cosmetics and this plant belongs to the family Solanaceae.

A.Bryophyta – chlorophyllous, aquatic, embryophytic, archegoniatic, plants in the plant kingdom. These are also called amphibian of the plant kingdom.

B.Pteridophyta – Chlorophyllous, terrestrial, embryophytic, tracheophytes in the plant kingdom. These are also called vascular cryptogams.

C.Gymnosperms – Naked seeded plants in the plant kingdom.

D.Angiosperms -  Fruit producing plants in the plant kingdom. These are highly advanced plants. Hibiscus is an angiosperm.

So, the correct option is ‘ Angiosperms’.

The first level of classification among plants depends on whether the plant body is well-differentiated or not. The next level of classification is based on whether the differentiated body has special vascular tissues for the transport of water and other substances. Further classification is based on the ability to bear seeds and whether the seeds are naked or enclosed within fruits. 
Monera is a kingdom that contains unicellular organisms with no nuclear membrane, such as bacteria. It can be divided into Archaebacteria and Eubacteria.
A fungus is any member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. Penicillium and Yeast both belong to group fungi.

Different types of epiphytes may grow on the same tree, including orchids. The name 'epiphyte' comes from the Greek word 'epi' meaning 'upon' and 'phyton' meaning 'plant'

Melia azedarach is commonly known as the Persian lilac or umbrella tree due to its canopy shape. The other options refer to different types of plants or algae.

In Bentham and Hooker's classification, the series Thalamiflorae is characterized by flowers having a superior ovary with the stamens inserted on the receptacle (thalamus) below the ovary, meaning there is an absence of a nectariferous disc below the ovary.

Ulothrix is a genus of filamentous green algae, generally found in fresh and marine water. They are eukaryotic and unicellular. The plant body consists of unbranched, uniseriate filaments. The Ulothrix is a thallophyte having undifferentiated bodies. Funaria are nonvascular plants, i.e., they do not have conductive tissues and they perform transport of water and nutrients by diffusion; they are cryptogamic, they are small in size; in their life cycle the lasting form is haploid (the gametophyte) and the sporophyte depends on the gametophyte to survive. Hence it is a bryophyte. The living species of heterosporous pteridophytes are small herbaceous perennials like Marsilea. These pteridophytes possess only one kind of non-sexual reproductive spores and possess the true fibro-vascular system, true roots, and leaves. The genus Pinus can be distinguished by long needles on very short shoots in bundles of 2,3, or 5, strobili on long shoots, and the shoots and foliage are strongly dimorphic. Male and female flowers are separate structures: the female flowers are the structures that will eventually become the familiar cones containing the seeds, and male flowers release pollen, which is then captured by the female cones. Gymnosperm seeds develop either on the surface of scales or leave, often modified to form cones. Thus pinus is a gymnosperm. Ficus is an angiosperm because they are seed-producing plants and have flowers, endosperm within the seeds, and the production of fruits that contain the seeds.

Mosses are small flowerless plants that usually grow in dense green clumps or mats, in damp or shady locations. They are bryophytes in the nature.

• Angiosperms are flowering plants. They reproduce by the formation of gametes and flowers act as reproductive organs. 
• Parts of the flower include petals, sepals, one or more carpels (the female reproductive structure) and stamens (the male reproductive structure)
• So, the correct answer is 'Flowers'
  

• The flowering plants (angiosperms) are divided into two groups, namely monocots and dicots. 
• Monocots- Plants which have only one cotyledon in the seeds are called as monocots. For example, maize, banana, garlic, etc.
• Dicots- Plants that have two cotyledons in their seeds are called as dicots. For example, mustard, beans, legumes, apples, etc.

• Cotyledons are actually part of the seed. 
• They are the first part of the plant to emerge and they look like little green leaves (hence, "seed leaves"). 
• The cotyledons store food reserves for the growing seedling. The plant relies on this stored food for early growth. 
• The cotyledons also can photosynthesize, which supplies extra energy until the first true leaves emerge.

• The angiosperms are divided into two groups on the basis of the number of cotyledons present in the seed. 
• The plants with seeds having single cotyledons are known as monocots. The plants with seeds having two cotyledons are known as dicots.