Question

With the help of a neat labelled diagram explain the structure of microsporangium​

Answer 1

Explanation:

Microsporangium is the sporangial structure which contains microspores which are the pollen sacs giving rise to male gametes in an angiosperm. A microsporangium is circular in outline in transverse section and is usually surrounded by four wall layers. The outermost is the single layer of the epidermis. The second layer is endothecium, where cells develop thickenings. The middle layer is made up of 2-4 cells. The innermost layer is tapetum, which provides nutrition to the developing pollen cells. The cells of tapetum may be multinucleate. The outer three layers are protective in function. They also help in dispersal of pollens by dehiscing themselves. There are four pollen sacs present inside. The centre of the microsporangium comprises of compact sporogenous tissue. These tissues undergo meiotic divisions to form microspore tetrads, that further divide to form pollen grains.

Answer 2

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★ A ᴛʏᴘɪᴄᴀʟ ᴍɪᴄʀᴏsᴘᴏʀᴀɴɢɪᴜᴍ ᴀᴘᴘᴇᴀʀs ᴄɪʀᴄᴜʟᴀʀ ᴀɴᴅ ɪs sᴜʀʀᴏᴜɴᴅᴇᴅ ʙʏ ғᴏᴜʀ ᴡᴀʟʟs:

(ɪ) ᴇᴘɪᴅᴇʀᴍɪs: ɪᴛ ɪs ᴛʜᴇ ᴏᴜᴛᴇʀᴍᴏsᴛ sɪɴɢʟᴇ ʟᴀʏᴇʀ ᴏғ ᴄᴇʟʟ ᴡʜɪᴄʜ ɪs ᴘʀᴏᴛᴇᴄᴛɪᴠᴇ ɪɴ ɴᴀᴛᴜʀᴇ.

(ɪɪ) ᴇɴᴅᴏᴛʜᴇᴄɪᴜᴍ: ɪᴛ ɪs ᴛʜᴇ sᴇᴄᴏɴᴅ ʟᴀʏᴇʀ ᴡɪᴛʜ ᴛʜɪᴄᴋ ᴄᴇʟʟs, ʜᴇʟᴘ ɪɴ ᴅᴇʜɪsᴄᴇɴᴄᴇ ᴀɴᴅ ɪs ᴘʀᴏᴛᴇᴄᴛɪᴠᴇ ɪɴ ɴᴀᴛᴜʀᴇ.

(ɪɪɪ) ᴍɪᴅᴅʟᴇ ʟᴀʏᴇʀ: ɪᴛ ɪs ᴛʜᴇ ᴛʜɪʀᴅ ʟᴀʏᴇʀ ᴄᴏᴍᴘᴏsᴇᴅ ᴏғ 1-3 ʟᴀʏᴇʀs ᴏғ ᴄᴇʟʟs, ʜᴇʟᴘ ɪɴ ᴅᴇʜɪsᴄᴇɴᴄᴇ ᴀɴᴅ ɪs ᴘʀᴏᴛᴇᴄᴛɪᴠᴇ ɪɴ ɴᴀᴛᴜʀᴇ.

(ɪᴠ) Tᴀᴘᴇᴛᴜᴍ: ɪᴛ ɪs ᴛʜᴇ ғᴏᴜʀᴛʜ ᴀɴᴅ ɪɴɴᴇʀᴍᴏsᴛ ʟᴀʏᴇʀ ᴏғ ᴄᴇʟʟ ᴡɪᴛʜ ᴅᴇɴsᴇ ᴄʏᴛᴏᴘʟᴀsᴍ ᴀɴᴅ ᴍᴀɴʏ ɴᴜᴄʟᴇɪ. ɪᴛ ᴘʀᴏᴠɪᴅᴇs ɴᴏᴜʀɪsʜᴍᴇɴᴛ ᴛᴏ ᴛʜᴇ ᴅᴇᴠᴇʟᴏᴘɪɴɢ ᴘᴏʟʟᴇɴ ɢʀᴀɪɴs.

★ᴛʜᴇ ᴄᴇɴᴛʀᴇ ᴏғ ᴇᴀᴄʜ ᴍɪᴄʀᴏsᴘᴏʀᴀɴɢɪᴜᴍ ɪs ғɪʟʟᴇᴅ ᴡɪᴛʜ ᴄʟᴏsᴇʟʏ ᴀʀʀᴀɴɢᴇᴅ sɪᴍɪʟᴀʀ ᴄᴇʟʟs ᴄᴀʟʟᴇᴅ sᴘᴏʀᴏɢᴇɴᴏᴜs.

★ᴀᴛ ᴍᴀᴛᴜʀɪᴛʏ, ᴘᴏʟʟᴇɴ sᴀᴄ ɪs ғᴏʀᴍᴇᴅ ʙʏ ғᴜsɪᴏɴ ᴏғ ᴛᴡᴏ ᴍɪᴄʀᴏsᴘᴏʀᴀɴɢɪᴜᴍ ɪɴᴇᴀᴄʜ ʟᴏʙᴇ.

★ᴀ ᴍᴀᴛᴜʀᴇ ᴀɴᴛʜᴇʀ ᴅᴇʜɪsᴄᴇs ʙʏ sʟɪᴛs ᴀɴᴅ ʟɪʙᴇʀᴀᴛᴇ ᴛʜᴇ ᴘᴏʟʟᴇɴ ɢʀᴀɪɴ.