Biology
Planning
Introduction
Stomata are pores on the bottom of leaves of vascular plants. The function of stomata is to allow gaseous exchange (transpiration) between the plant and the external environment (see diagrams below). This process is carried out by the plant, which controls the opening and closing of stomata via the guard cells. The more stomata a leaf contains the greater the rate of gas exchange and the less water it will be able to accumulate. Stomatal pores are formed between pairs of specialised guard cells. The wall adjacent to the stomata is thicker than the other walls. When a guard cell swells or shrinks due to the gain or loss of water, the thickened wall is the only one to maintain its form. Consequently when the guard cells shrink, they shift towards each other, closing the stomata. Water enters the guard cells by osmosis. The amount and direction of movement of water is influenced by several factors, one of which is light. Light has an indirect effect. The guard cells of stomata through which most water loss comes about by transpiration are sensitive to light intensity. They open during periods of light and close as the light intensity falls. These changes allow transpiration either to take place or not. Another factor which affects whether stomata stay open or closed is the water balance of the plant. If a plant carries on to lose more water to the air than it can gain from the soil, the stomata eventually close. This decreases water loss by transpiration and allows the plant time to restore its water balance.
Aim
I will carry out a method that is valid and reliable to allow me to investigate if there is a statistically significant difference in stomatal density ( the number of stomata in a specified area of a leaf) between two temperate plant leaves (the Holly and the Privet) and two tropical plant leaves (the Mexican Snowball and the Aloe Vera).
Hypothesis
There is a
Introduction
Stomata are pores on the bottom of leaves of vascular plants. The function of stomata is to allow gaseous exchange (transpiration) between the plant and the external environment (see diagrams below). This process is carried out by the plant, which controls the opening and closing of stomata via the guard cells. The more stomata a leaf contains the greater the rate of gas exchange and the less water it will be able to accumulate. Stomatal pores are formed between pairs of specialised guard cells. The wall adjacent to the stomata is thicker than the other walls. When a guard cell swells or shrinks due to the gain or loss of water, the thickened wall is the only one to maintain its form. Consequently when the guard cells shrink, they shift towards each other, closing the stomata. Water enters the guard cells by osmosis. The amount and direction of movement of water is influenced by several factors, one of which is light. Light has an indirect effect. The guard cells of stomata through which most water loss comes about by transpiration are sensitive to light intensity. They open during periods of light and close as the light intensity falls. These changes allow transpiration either to take place or not. Another factor which affects whether stomata stay open or closed is the water balance of the plant. If a plant carries on to lose more water to the air than it can gain from the soil, the stomata eventually close. This decreases water loss by transpiration and allows the plant time to restore its water balance.
Aim
I will carry out a method that is valid and reliable to allow me to investigate if there is a statistically significant difference in stomatal density ( the number of stomata in a specified area of a leaf) between two temperate plant leaves (the Holly and the Privet) and two tropical plant leaves (the Mexican Snowball and the Aloe Vera).
Hypothesis
There is a