Question

Describe the structure of microsporangium for 5 marks

Answer 1

It is surrounded by four layers:
The outermost is the single layer of epidermis.
The second layer is endothecium, where cells develop thickenings.
Middle layer is of 2-4 cells.
Tapetum, the innermost layer which provides nutrition to the developing pollen cells. The cells of tapetum may be multinucleate.
There are four pollen sacs.
There is a group of compactly arranged homogenous cells called sporogenous tissue in the centre of each sac.

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.