Botany and Plant Science

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.

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).

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).

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.

• 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'
  

Radical leaves are those that arise from a reduced stem, often appearing to emerge directly from the root or ground level. Cauline leaves arise from the aerial stem, while ramal leaves arise from branches.

• Phloem is also called as bast. 
• These tissues in plants conduct foods made in the leaves to all other parts of the plant. 
• Phloem is composed of various specialized cells called sieve tubes, companion cells, phloem fibers, and phloem parenchyma cells.
• Hence, Phloem is a food synthesizing tissue.

Plant tissues are categorized into epidermal, ground, and vascular tissue systems. The leaf mesophyll, consisting of palisade and spongy parenchyma, performs photosynthesis and belongs to the ground tissue system.

Xylem conducts water and minerals to different parts of the body which can be used for photosynthetic reaction and for several metabolic processes.
Phloem is responsible for transporting sugars, proteins and other organic molecules in plants. It is a vascular tissue in land plants primarily responsible for the distribution of sugars and nutrients manufactures in the shoot.

Phloem is responsible for transport of food and minerals. Food synthesized in photosynthetic parts is translocated to non-photosynthetic parts through phloem. Food is transported in multi-directional fashion.