Role of Stomata & Control
Stomata : a pore found in the epidermis of plants which are used to control as exchange Main function of stomata : Allow enough C02 to enter the leaf to optimize photosynthesis, while conserving as much water as possible
Structure of stomata
* Each stomata consists of a stoma (minute pore) which are surrounded by 2 guard cells. * Stomata closes and opens according to the turgidity of the guard cells * Stomata also allows for cooling of the leaf by loss of water through transpiration to lower leaf temperature * Guard cells open and close to control the exchange between a plant and the environment. They act as an entry point for CO2 in photosynthesis and an exit point for water vapour from transpiration. * Guard cells contain chloroplast and have uneven thick walls. * Shape of guard cells differ in monocotyledons and dicotyledons, however the mechanism remains the same. Control of Stomatal Movement and Their Role In Transpiration and Photosynthesis -Waxy cuticle on leaf acts as an effective barrier to water movement -restricts diffusion through the leaf so water vapour and other gases are exchanged via the leaf stomata. -If stomata is closed and temperature is stable, then air contained in the leaf will be saturated with water vapour as normal. -Opening and closing of stomata controls exchange of water vapour and oher gases across the leaf surface. Mechanism of Stomata
-stomata present on both sides of leaves but more frequent on lower surface of leaf. -usually present in equal numbers on both sides due to position of leaf towards the sun -Stomata contains air spaces that make up 15-40% of total leaf volume -Space contains air saturated with water that has evaporated from damp surfaces of the mesophyll cells Stomatal Movements
-stomata opening occur when solutes are accumulated in the guard cells, causing osmotic movement of water into the guard cells. -Builds up turgid pressure in...
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