What is the stomatal density on the upper and lower epidermis of hibiscus and colacasia leaves?

What is the stomatal density on the upper and lower epidermis of hibiscus and colacasia leaves?

• hibiscus is mesophyte and colacasia is monocot

• Answer:

  We wonder why you ask this question? Do you have reason to believe that stomatal density is related to whether a plant is a dicot or monocot? The most significant difference between the stomata of monocots and dicots is the design of the guard cells - the monocots having the dumbell type, and dicots the pair-of -sausage type. Also the monocots have them arranged in regular arrays, whereas the dicots have more of a crazy-paving of them! The role of stomata is to enable gaseous exchange whilst trying to minimise the consequent water loss. We guess that stomatal density stated in terms of "number of stomata per square mm" would also depend on the size of the stomata. Some plants may have many small stomata whilst others have few large ones. However, each would aim to achieve the same effect in terms of gaseous exchange and water evaporation. Monocots have stomata on both the "upper" and "lower" surfaces of their leaves, whilst SOME (but not ALL) dicots have stomata on only one surface (usually the lower one), so on this basis, to achieve the same effect, a monocot may need half the stomatal density of a dicot of a type with stomata on only one surface. However, many dicots have stomata on BOTH surfaces and some aquatic plants with floating leaves have stomata on the upper surface, so it is not possible to generalise about ALL monocots and ALL dicots. However, as a "stoma" is strictly speaking, the hole in the structure, we might guess that the total stomatal area per square mm of leaf surface would be the same for the same amount of gaseous exchange/transpiration. We would normally expect stomatal density to be related to the climate in which the plant is adapted to grow. Some cacti have no leaves, but green stems instead, perhaps because there is a lower stomatal density on stems than on leaves - the leaves have been reduced to the spines on the cactus. The stomata on such xerophytes may be in deep pits or in the folds of leaves. We would guess that xerophytes have a lower stomatal density than mesophytes. A monocot which is good for studying is Red Hot Poker (Kniphofia) becasue the epidermis peels off so easily.