Presentation on stomata

It is a short presentation on Stomata.

1. Welcome To My Presentation 3/29/2018 1

2. Topic Name : Stomata 3/29/2018 2

3. Outline…. Definition of stomata. Structure of stomata. Processes of opening and closing of stomata. Mechanism of stomata . What are the factors affecting stomata movement ? 3/29/2018 3

4. What is Stomata ? Stomata are pore in a plants skin through which water and gases are exchanged the plant and the atmosphere . 3/29/2018 4

5. Structure of stomata Each stoma in surrounded by a pair of kidney shaped guard cells. Each guard cell is a modified epidermal cell showing a prominent nucleus, cytoplasm and plastids . The wall of the guard cell is differentially thickened. The inner wall of each guard cell facing the stomata is concave and is thick rigid . 3/29/2018 5

6. The guard cells are surrounded by a variable number of epidermal cells called subsidiary cells . 3/29/2018 6

7. Opening and closing of stomata Opening and closing of stomata takes place due to changes in turgor pressure of guard cells . During the day water from subsidiary cell enters the guard cell making the guard cells fully turgid and the stomata open. During night time, water from guard cells enters the subsidiary cells and as a result the guard cells become flaccid due to decrease in turgor pressure and the stomata close . 3/29/2018 7

8. Mechanism of stomata Many theories have been proposed regarding opening and closing of stomata . Some important theories are given bellow.. 1. Theories of photosynthesis in guard cell . 2 . Starch sugar inter conversion theory . 3. Theory of glycolate metabolism . 4. Active potassium transport ion concept. 3/29/2018 8

9. Active k+ transport ion concept The concept of k+ ion transport was given by Fujino. It was supported and elaborated by Levitt and Rashke in 1975. it was appears to be an active mechanism which needs ATP. Explanation the mechanism as follows … Opening of stomata during day time (in present of light) Closing of stomata in Absence of Light (Darkness/ Night time) . Role of plant Hormones in Stomata Movements. 3/29/2018 9

10. Opening of stomata during day time Opening of stomata depends upon following conditions : Presence of light. Decrease in starch contents of guard cells. Increase concentration of malic acid in guard cells. Influx of k+ ions in guard cells. Efflux of H+ ions from guard cells . 3/29/2018 10

11. Con.. Intake of cl+ ions by guard cells. Low co2 concentration in an around guard cells. High pH (more than 7) in guard cells. High T.P in guard cells due to endosmosis. 3/29/2018 11

12. Closing of stomata in Absence of Light Closing of stomata depends on following conditions: Absence of light. Decreased concentration of malic acid in guard cells. Efflux of K+ ions from guard cells. Acidic medium of the cell sap in guard cells. Loss of Cl- ions from guard cells. 3/29/2018 12

13. Con… Increase CO2 concentration in and around the guard cells. Presence of plant growth inhibiting hormone abscissic acid . 3/29/2018 13

14. Factors affecting stomatal movement Light: light greatly influences the opening and closing of stomata. It is stimulates production of malic acid due to conversion of starch to sugar. Stomata so not open in U-V light and green light but remain opened in the the blue and red regions of the spectrum. 2. Temperature : Stomata open with rise in temperature and close at lower temperature as light and temperature are directly are directly related. Higher temperature also case stomatal closure . 3/29/2018 14

15. 3.Potassium chloride : Accumulation of potassium chloride causes opening of stomata 4.Organic Acid: The increase of organic acid content in the guard cells causes stomata to open. 5.Carbondioxide concentration: At low concentration of CO 2, the stomata open. with increase in the concentration of CO2 ,the stomata begin to close and when CO2 concentration of cells is higher than its concentration in the air, the stomata completely close. 3/29/2018 15

16. 6.water: water is responsible for causing changes in the turgor off the guard cells. Guard cells become flaccid on losing water and stomata close. when the guard cells become fully turgid on water and stomata open. 7. Abscisic: Abscisic acid accumulates in the leaves when the plants experience water stress or water deficit. It has been observed that ABA stimulates closure of stomata under these condition. 3/29/2018 16

17. Conclusion We know that stomata is a pore in a plants skin and usually it is limited on the lower sides of the leaves. In monocots seed the stomata are equally distributed on all sides and in aquatic plants stomata are present on the upper surface . 3/29/2018 17

18. 3/29/2018 18