Question

Now describe the flower with these terms: dicot/monocot, complete/incomplete, perfect/imperfect, regular symmetry/irregular symmetry, florescence?

Tell about what type of insect might be the pollinator for this flower. What type of characteristics would make it a good fit for that insect?

With a paragraph, explain to meiosis. Include the steps that happen and the purpose of meiosis in a plant.

Answer 1

Ans)The given flower ,sunflower also known as Wild Helianthus Annus can be described as follows-

Sunflowers are tall annual perrineal plants with a height of 300 cm.They are dicots.The large flower head is actually an inflorescence also known as a composite flower.It is made up of two kinds of tiny florets, disc florets (centre) and ray florets (outer ring).

Each disc floret is a perfect flower with a stamen and a pistil.

The ray florets are bilaterally symmetrical while the disc florets are radially symmetrical.

There is entomophily in sunflower and it is usually pollinated by bees.

Capitulum or head is the characterstic inflorescence of sunflower.The flower-heads of the sunflower are suited for insects(bees) as the crowding of the flowers ensures conspicuousness and the pollination of a maximum number of flowers by a single insect visit.Also bees are attracted by standard floret.The brightly colored petals attract the insect.The pollen grains are very efficiently exposed to the incoming insect resulting in successful cross pollination and no self pollination in the flower itself.

Meiosis is a type of reductional Division where the number of chromosomes are reduced to half. It is basically used in the production of gametes from gametocyte cells. The purpose of meiosis in a plant is to produce the haploid male gametes and the female gametes on the reproductive structures during sexual reproduction

Stages of meiosis are as follows-

Stages of Meiosis I

Prophase I

The chromosomes condense and move towards the centre of the cell. It has five sub-phases:

• Leptotene: The homologous chromosomes replicate.
• Zygotene: Synapsis between homologous chromosomes start.
• Pachytene: The sister chromatids separate but the homologous chromosomes remain attached.
• Diplotene: The two homologous chromosomes migrate apart and disintegrate between the chromosomal arms.
• Diakinesis: The condensation of chromosomes stop at this stage and the chiasmata is clearly visible under an electron microscope. The nucleolus and the nuclear envelop disappear at this stage and the centrosome moves to the equator.

Metaphase I

Homologous chromosomes line up on the metaphase plate to be separated.

Anaphase I

Separated chromosomes are pulled towards the centrioles on either side of the cell.

Telophase I

Chromosomes are completely pulled apart and new nuclear envelope forms.

Stages of Meiosis II

Prophase II

Nuclear envelope disintegrates and centrioles develop.

Metaphase II

Chromosomes line up on the metaphase plate and the chromatids are on either side of the metaphase plate.

Anaphase II

Sister chromatids separate and are known as sister chromosomes.

Telophase II

Cell divides into two and new nuclear envelope surrounds the chromosomes

Because the number of chromosomes are reduced to half it is known as reductional division.