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Physics, Chemistry and Biology: Post your doubts here!

Phoenix Blood

Phoenix Blood

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Ofcourse, phloem transports amino acids and sucrose up to down (leaf to roots and growing and storage organs) , but sometimes, why does it transport food substances upwards, apart from tubers sending up their foodstore?
 
Karim Nabil

Karim Nabil

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Phoenix Blood >>well i finished bio ol and currently AS student but i can help you though;)
  1. xylem dies and its protoplasm(cell content) disintegrates to decrease resistance to water and minerals conducted, its also has cell wall made of lignin which provides support for the xylem tissue because water moved with strong forces such as transpiration pull and cohesion forces
  2. phloem sieve tubes unload sucrose from source to sink , sugars(sucrose) made by photosynthesis and then transported to the sink cells whether it is upward or downward depending on the concentration gradient
  3. stomata mostly located on the underside of the leaf beacuse plants under direct sunlight would constantly have their stomata open and would thus lose much water and the plant dies.
  4. respiration occurs in mitochondria where glucose provided by photosynthesis from chloroplasts is oxidised/respired to produce energy(in the form of ATP)
  5. plasmolysis is the pulling away of cytoplasm from the cell wall, this occur if plant cell is placed in a higher concentrated solution, as a result cell became flaccid
 
H

Heba A.Moety

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Phoenix Blood said:
Why are stomata mostly located on the underside of the leaf, as in most dicots?
Click to expand...
1) The number of stomata (not stomatas) on the upper surface is drastically reduced as the upper leaf surface receives more intense and direct sunlight and tends to lose more water from that surface.

2) This is compensated by increasing the stomata quantity on the lower surface

3) The internal leaf structure is accordingly adapted for more photosynthesis (Palisade nearer the upper surface for efficient photosynthesis and loosely arranged spongy parenchyma for good gaseous exchange.

4) In drought prone areas the stomata are entirely absent from the upper surface and the epidermis is thickly circularized to reduce transpiration.( Eucalyptus and Cycas )

5) In extreme desert condition, the leaves are totally dispensed and the stem is a phylloclade (See Cacti.)
Source:
Botanist
 
Phoenix Blood

Phoenix Blood

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Heba A.Moety said:
1) The number of stomata (not stomatas) on the upper surface is drastically reduced as the upper leaf surface receives more intense and direct sunlight and tends to lose more water from that surface.

2) This is compensated by increasing the stomata quantity on the lower surface

3) The internal leaf structure is accordingly adapted for more photosynthesis (Palisade nearer the upper surface for efficient photosynthesis and loosely arranged spongy parenchyma for good gaseous exchange.

4) In drought prone areas the stomata are entirely absent from the upper surface and the epidermis is thickly circularized to reduce transpiration.( Eucalyptus and Cycas )

5) In extreme desert condition, the leaves are totally dispensed and the stem is a phylloclade (See Cacti.)
Source:
Botanist
Click to expand...

Karim Nabil said:
Phoenix Blood >>well i finished bio ol and currently AS student but i can help you though;)
  1. xylem dies and its protoplasm(cell content) disintegrates to decrease resistance to water and minerals conducted, its also has cell wall made of lignin which provides support for the xylem tissue because water moved with strong forces such as transpiration pull and cohesion forces
  2. phloem sieve tubes unload sucrose from source to sink , sugars(sucrose) made by photosynthesis and then transported to the sink cells whether it is upward or downward depending on the concentration gradient
  3. stomata mostly located on the underside of the leaf beacuse plants under direct sunlight would constantly have their stomata open and would thus lose much water and the plant dies.
  4. respiration occurs in mitochondria where glucose provided by photosynthesis from chloroplasts is oxidised/respired to produce energy(in the form of ATP)
  5. plasmolysis is the pulling away of cytoplasm from the cell wall, this occur if plant cell is placed in a higher concentrated solution, as a result cell became flaccid
Click to expand...

Thank you!! :)
 
Phoenix Blood

Phoenix Blood

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The embryo turns into a seed or a fruit? Pertaining to this, what are the endosperm and the cotyledon? Cotyledon is the food store or leaf?
 
Phoenix Blood

Phoenix Blood

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Awesome12 said:
None. The ovary becomes the seed. The ovary wall becomes the fruit. The endosperm is formed from the endosperm nucleus. Cotyledon is the food store
Click to expand...

And what about the seed leaves? Arn't they the cotyledons? (...basing some logic from the words monocots and dicots...)
 
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