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BIOLOGY in Marathi

Understanding is IMPORTANT.......

Prof. Deshmukh A. B.'s Biology Class

https://www.onlinesciencestudy.com

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Prof. A. B. Deshmukh's Biology Class

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1. REPRODUCTION IN LOWER & HIGHER PLANTS

-CREATED BY-

PROF. DESHMUKH A. B.

ASST. TEACHER

SEC. & HIGHER SEC. SCHOOL, SHENDI (BHANDARDARA DAM), TAL. – AKOLE, DIST. - AHMEDNAGAR

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1.10 Development of Endosperm :

  • The triploid primary endosperm nucleus repeatedly divides, mitotically to form nutritive tissue, called endosperm.
  • In post-fertilization
    • changes within the ovule, the embryo and endosperm are seen to develop simultaneously.
  • The other cells of embryo sac disorganized sooner or later.
  • The formation of triploid endosperm nucleus triggers cell division which leads to the formation of endosperm.

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  • There are three types of endosperms on the basis of mode of development.
  • These are --

i. Nuclear type,

ii. Cellular type,

iii. Helobial type

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a. Nuclear endosperm :

  • It is the most common type found in 161 angiospermic families.

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Primary Endosperm Nucleus

PEN

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Here, the PEN repeatedly divides mitotically without wall formation to produce large number of free nuclei.

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A big central vacuole appears in the centre of cell pushing the nuclei towards the periphery.

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Later, walls develop between the nuclei, hence multicellular endosperm is formed.

But in several cases cell wall formation remains incomplete.

e.g. wheat, sunflower and coconut.

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  • Coconut has multicellular endosperm in the outer part and free nuclear as well as vacuolated endosperm in the centre.

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b. Cellular endosperm :

  • In some plants, division of triploid primary endospermic nucleus is immediately followed by wall formation.
  • So that the endosperm is cellular right from the beginning.
  • It is mostly observed in 72 families of dicots as in members

e.g. Balsam, Petunia, Adoxa, etc.

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Balsam

Petunia

Adoxa

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c. Helobial endosperm :

  • It occurs in the order Helobiales of monocotyledons.
  • In this case, first division of primary endosperm nucleus is followed by a transverse wall, which divides the cell unequally.
  • The smaller cell is called chalazal cell and larger cell is the micropylar cell.
  • Then the nuclei in each cell divide by free nuclear divisions and then walls develop between nuclei in micropylar chamber.
  • It is intermediate between cellular and nuclear type endosperm

e.g. Asphodelus.

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Asphodelus

C

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