Why is there more stomata in the lower epidermis than that of the upper epidermis in the leaf?

Answer 1

First of all let us revise the functions of stomata (singular stoma).

These pores on the leaves perform two functions, viz. i) Gaseous exchange ii) transpiration.

The first is essential for respiration, photosynthesis, and the second for to pull the water column up (transpiration pull) and to get rid of EXCESS water.

More often than not, a plant continues to lose water through the stomata even when it is water deficient.

That is why transpiration is termed ‘Necessary Evil’
To reduce the impact of this Evil, a plant / leaves resort to any one or all of the following.

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.)

Answer 2

Lower Epidermis

Answer 3

The leaf is a factory designed to make food efficiently. The top part of the leaf contains palisade mesophyll close to the surface. These cells are long and skinny and packed tightly together. There is little or no space between them. Their chloroplasts circle like a Ferris wheel picking up light for the reactions to come. The area just below this is called the spongy layer. Here the mesophyll cells are larger and have spaces between them. These spaces are directly connected to the openings on the bottom of the leaf called the stomata. There is no such thing as stomatas. Stomata is plural. These stomata are controlled by two bean shaped cells called guard cells. The guard cells allow carbon dioxide in and water vapor and oxygen out. So as you can see the more stomata on the bottom the more carbon dioxide comes in to be used with the sunlight coming in from the other side. Also the leaf can only face the sun one side at a time.

Answer 4

During the day tine as the sunlight falls on the plant leaf the amount of water present in the plant gets evaporated due to the presence of small open stomatal pore.If more somatal present pores are present in the upper side due to high rate of evaporation from the upper epidermal the water present in the plant gets evaporated and the amount of water in plants may lower dow. So in order to prevent this more stomata are present in the lower epidermis than upper epidermis.

Answer 5

get a picture of leaf crossection under microscope

- you will see that the tissue under the upper epidermis is more packed together, more compact - this way it serves the purpose of catching the energy of sun (the palisade parenchyme) as effectively as could be, while the tissue next to lower epidermis is more loose with alot of air pockets (sponge parenchym)-the system of air cavities is connected to stomatas. this tissue doesnt get as much light as the upper side and it contains less cells, less chlorophylls and it is meant for gas exchange - because photosynthesis requires good exchange of gasses. this specialization of both part of leaves makes good sense because light comes from above. also when it is raining the stomatas couldnt function if clogged by water.

the reason palisade parenchyme is the way it is is that the light can travel through the long stright narrow crevices between them - in order to get deeper inside the leaf, in the sponge parenchym. if there were as many stomatas in the upper epidermis, they would require some air pockets in the leaf under them so that the air gets in and through the leaf - and this means less light would be absorbed

Answer 6

If it were not so, plant would lose most of its water through transpiration as the direct rays of the sun falling on the upper part of the leaf would favour transpiration by increasing the transpiration- rate. I hope you know that sunlight increases transpiration by favouring the opening of stomata.

Answer 7

I bet your the hit of the party....