Biology FRUITS AND SEEDS

KEY TOPICS

`star` Fruit
`star` Seed
`star` Structure of Dicot Seed
`star` Structure of Monocot Seed

FRUIT

● The fruit is a characteristic feature of the flowering plants.

● It is a `color{Violet}"mature or ripened ovary"`, developed after fertilisation.

● If a fruit is formed `color{Violet}"without fertilisation"` of the ovary, it is called a `color{Violet}"parthenocarpic fruit"`.

● `color{Brown}"Parts"`:
`star` Generally, the fruit consists of a wall or `color{Violet}"pericarp"` and seeds.

`star` The pericarp may be `color{Violet}"dry or fleshy"`.

`star` When pericarp is thick and fleshy, it is differentiated into the `color{Violet}"outer epicarp"`, the `color{Violet}"middle mesocarp"` and the `color{Violet}"inner endocarp"`.

● In mango and coconut, the fruit is known as a `color{Violet}"drupe"`.

● They develop from `color{Violet}"monocarpellary superior ovaries"` and are one seeded.

● E.g.: In mango the pericarp is well differentiated into an outer `color{Violet}"thin epicarp"`, a middle `color{Violet}"fleshy edible mesocarp"` and an inner `color{Violet}"stony hard endocarp"`.

● E.g.: In coconut, the `color{Violet}"mesocarp is fibrous"`.

SEED

● The `color{Violet}"ovules after fertilisation"`, develop into seeds.

● `color{Brown}"Parts"` :
`star` A seed is made up of a `color{Violet}"seed coat"` and an `color{Violet}"embryo"`.

`star` The embryo is made up of a `color{Violet}"radicle and plumule"`, an `color{Violet}"embryonal axis"` and one (as in wheat, maize) or two `color{Violet}"cotyledons"` (as in gram and pea).

STRUCTURE OF A DICOTYLEDONOUS SEED

● `color{Brown}"Parts"`:
`star` The outermost covering of a seed is the `color{Violet}"seed coat"`.

`star` The seed coat has `color{Violet}"two layers"`, the outer `color{Violet}"testa"` and the `color{Violet}"inner tegmen"`.

`star` The `color{Violet}"hilum is a scar"` on the seed coat through which the developing seeds were attached to the fruit.

`star` Above the hilum is a small pore called the `color{Violet}"micropyle"`.

`star` Within the seed coat is the embryo, consisting of an embryonal axis and two cotyledons.

`star` The `color{Violet}"cotyledons are often fleshy"` and full of reserve food materials.

`star` At the two ends of the embryonal axis are present the radicle and the plumule.

● `color{Brown}"Endosperm"` :
`star` `color{Brown}"Endospermous"` : In some seeds such as castor the endosperm formed as a result of double fertilisation, is a `color{Violet}"food storing tissue"` which persists in the mature seeds . Such seeds are called `color{Violet}"albuminous or endospermous seeds"`.

`star` `color{Brown}"Non Endospermous"`: In plants such as bean, gram and pea, the endosperm is not present in mature
seeds and such seeds are called `color{Violet}"non endospermous"`.

STRUCTURE OF MONOCOTYLEDONOUS SEED

● Generally, monocotyledonous seeds are `color{Violet}"endospermic"` but some as in orchids are `color{Violet}"non-endospermic"` .

● In the seeds of cereals such as maize the seed coat is `color{Violet}"membranous"` and generally fused with the `color{Violet}"fruit wall"` .

● The endosperm is `color{Violet}"bulky"` and stores food.

● The outer covering of endosperm separates the embryo by a proteinous layer called `color{Violet}"aleurone layer"` .

● The embryo is small and situated in a `color{Violet}"groove"` at one end of the endosperm.

● It consists of one large and `color{Violet}"shield shaped cotyledon"` known as `color{Violet}"scutellum"` and a short axis with a plumule and a radicle.

● The `color{Violet}"plumule"` and `color{Violet}"radicle"` are enclosed in sheaths which are called `color{Violet}"coleoptile"` and `color{Violet}"coleorhiza"` respectively.


 
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