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describe the structure of angiosperm flower give some evidences in support to the view that flower is modified shoot

Dear Student,

Structure of China rose flower ( An angiosperm flower)

A flower usually consists of four main parts.

  • Sepals

They are the small, leaf-like green structures of a flower. They can be clearly distinguished as separate structures in flowers such as rose, marigold, etc. However, sepals are found to be fused in flowers such as periwinkle, Hibiscus, etc.

  • Petals

They are the brightly colored, prominent parts of an open flower.

Stamens and pistils are the two reproductive parts of flowers.

  • Stamens

They are the male reproductive parts of plants. They can vary in number. A stamen is divided into two parts: anther and filament.

Stamens can be free, such as those present in Hibiscus, pea, marigold, etc., or they can be joined to petals, such as those in Datura, potato, sunflower, etc. The anther contains a number of pollen grains.

  • Pistils

They are the female reproductive parts of plants. They are present in the innermost parts of flowers. They consist of three parts: stigma, style, and ovary.

An ovary is the lowermost, swollen part of the pistil. It contains one or many small, bead-like structures called ovules. These ovules are attached to the ovary wall with the help of structures called placenta.

These ovules develop into seeds, and the entire ovary (containing the ovules) develops into a fruit.



Flower is the modified shoot i.e when a part of shoot mainly apical meristem gets modified, it forms a floral meristem that forms various parts of flower.
During the flowering season, the apical meristem gives rise to the floral meristem. The axis of the stem at this meristem gets condensed, while the internodes lie near each other. Instead of leaves, various floral appendages arise from the node and form a complete flower. Therefore, it can be said that the flower is a modified shoot that is formed from the apical meristem.
 
Regards.​​​​​​​

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Their ability to flower sets them apart from non-flowering plants, also known as gymnosperms, allowing them a successful means of reproduction. If you look closely into the flowers, you can see the trademark characteristics of angiosperms, including stamens, carpels, and tiny pollen grains.A flower is a modified shoot. A flower is a modified shoot. The meristem of the flower stem is determinate, meaning that once the flower parts are produced, no further cell division occurs. Flower parts, which are modified leaves, are arranged in whorls on the expanded apex of the flower stalk or pedicel...................
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The flower is a modified shoot as-
(I) Homology of the floral bud:A floral bud and a vegetative bud appear quite different externally, yet there is great similarity between the two.
(i) Floral and vegetative buds both emerge either in terminal or in axillary position
(ii) The floral buds may sometimes get modified in to vegetative buds or bulbils (e.g. Agave, Allium). Thus proving that the two are analogous structures.
(II) Axis nature of receptacle:
(i) Though in majority of cases, the internodes in floral axis remain highly reduced, yet in a number of plants such as Capparis, Gynandropsis​​​​​​​ Passiflora etc. the receptacle shows prominent nodes and internodes.​​​​​​​
(ii) Second evidence comes from monstrous development of foliage leaves in some flowers (e.g., rose, larkspur, pear etc.). In the flowerpot’ these plants, the receptacle of the flower continues its growth even after producing all the four types of floral appendages and then produces normal foliage leaves​​​​​​​.
(iii) A third evidence comes from Michelia champaca where the thalamus elongates like an ordinary stem beyond carpels and bears aggregate fruit.​​​​​​​
(III) Foliage nature of floral appendages:

(i) Phvllotaxy:

Foliage leaves and floral appendages have identical arrangement on the stem.​​​​​​​

(ii) Aestivation:

Pre-foliation of foliage leaves and aestivation of floral leaves (calyx and corolla) is virtually identical.

(iii) Foliar nature of sepal:

That sepal is a modified leaf can be clearly seen in Mussaenda. Hen- one of the sepals enlarges abnormally and becomes green like any foliage leaf.
​​​​​​​Flower is a modifield shoot

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