Factors which influence plant growth

Transcription

1 Factors which influence plant growth Environment Irradiation, Day-length, Temperature, Water availability, Gases Soil, Nutrients Plant Hormones

2 Growth Hormones

3 Auxins Cytokinins Gibberellins Ethylene Abscisic acid Brassinosteroids Jamonic acid

4 Growth Hormones Auxins: stimulates cell elongation, mediates tropism. Cytokinins: stimulates cell division, in ratio with auxins regulate meristematic cell division. Gibberellins: breaks seed dormancy. Abscisic acid: stimulates the closure of stomata. Ethylene: is associated with fruit ripening. Brassinosteroids: regulate plant stature (height). Jasmonic acid: give a response to wounding of plants and associated with pest resistance.

5 Photosynthesis Conversion of Solar Energy to Chemical Energy by Plants

6 Phytosynthesis ATP: Adenosine triphosphate (ATP). Adenosine diphosphate (ADP). Nicotinamide adenine dinucleotide phosphate (NADP + ). NADPH is the reduced form of NADP +, and NADP + is the oxidized form of NADPH.

7 Adenosine diphosphate (ADP) Adenosine triphosphate (ATP)

8

9 Photosynthesis in plants converts light energy in the form of photons into chemical energy in the form of ATP and NADPH

10 The energy stored in ATP and NADPH can then be used to convert CO 2 and H 2 O (water) into simple sugars

11 An added bonus of photosynthesis is the production of O 2 (oxygen) by the plant

12 Why is photosynthesis Important?

13 Photosynthesis Light Reaction Dark Reaction

14 Phytosynthesis Photosynthesis takes place in the chloroplasts and depends on the presence of chlorophyll and carotenoids. Chlorophyll and carotenoids are pigments that absorb specific wavelengths of sunlight. Chlorophyll absorbs red and blue light while scattering green light (hence plants look green).

15 Photosynthesis The chlorophyll and carotenoid pigments are found in the photosynthetic membrane within the chloroplasts in leaf mesophyll cells. There are two chlorophyll pigments, a and b found in the chloroplasts. They absorb red light and blue light. Carotenoid pigments will absorb blue light but not red light.

16 Photosynthesis Magnesium Purves et al., Life: The Science of Biology, 4th Edition

17 Photosynthesis When light energy hits the chlorophyll pigment it excites an electron in the pigment. This absorbed energy is used to split water producing hydrogen, oxygen and electrons that move in the photosynthetic electron transport system.

18 Photosynthesis O H H + O H H O 2 H + H + e - e - H + H + e - e -

19 UC Davis

20 Light reaction Dark reaction

21 Light H 2 O NADPH & H + Light Reaction ATP O 2

22 Dark reaction lumen

23 6 CO 2 Rubisco 12 molecules Ribulose-1-5-bisphosphate 3-Phosphoglycerate 6 molecules Calvin Cycle ATP ADP ADP ATP 3,1 Biophosphoglycerate Ribulose-5-phosphate 6 molecules 12 NADP & 12 NADPH Glucose 12 molecules Glyceraldahyde- 3-phosphate

24 Ribulose-1-5-bisphosphate 6 molecules

25 Ribulose-1-5-bisphosphate 6 molecules 6 CO 2

26 Ribulose-1-5-bisphosphate 6 molecules 6 CO 2

27 Ribulose-1-5-bisphosphate 6 molecules 6 CO 2 Rubisco

28 6 CO 2 Rubisco Ribulose-1-5-bisphosphate 6 molecules 12 molecules 3-Phosphoglycerate

29 6 CO 2 Rubisco Ribulose-1-5-bisphosphate 6 molecules 12 molecules 3-Phosphoglycerate ADP ATP 3,1 Biophosphoglycerate

30 6 CO 2 Rubisco Ribulose-1-5-bisphosphate 6 molecules 12 molecules 3-Phosphoglycerate ADP ATP 3,1 Biophosphoglycerate 12 NADP & 12 NADPH

31 6 CO 2 Rubisco Ribulose-1-5-bisphosphate 6 molecules 12 molecules 3-Phosphoglycerate ADP ATP 3,1 Biophosphoglycerate 12 NADP & 12 NADPH 12 molecules Glyceraldahyde- 3-phosphate

32 6 CO 2 Rubisco Ribulose-1-5-bisphosphate 6 molecules 12 molecules 3-Phosphoglycerate ADP ATP 3,1 Biophosphoglycerate 12 NADP & 12 NADPH Glucose C 6 H 12 O 6 12 molecules Glyceraldahyde- 3-phosphate

33 6 CO 2 Rubisco Ribulose-1-5-bisphosphate 6 molecules 12 molecules 3-Phosphoglycerate ADP ATP 3,1 Biophosphoglycerate Ribulose-5-phosphate 6 molecules 12 NADP & 12 NADPH Glucose C 6 H 12 O 6 12 molecules Glyceraldahyde- 3-phosphate

34 6 CO 2 Rubisco Ribulose-1-5-bisphosphate ATP ADP 6 molecules Ribulose-5-phosphate Glucose C 6 H 12 O 6 6 molecules 12 molecules Glyceraldahyde- 3-phosphate 12 molecules 3-Phosphoglycerate ADP 3,1 Biophosphoglycerate 12 NADP & 12 NADPH ATP

35 Dark reaction Light reaction lumen

36 Photosynthesis

37 Photosynthesis light 6CO H 2 O C 6 H 12 O H 2 O + 6O 2 energy

38 C-4 Plants Plant species such as corn, sorghum and sugar cane use a two step version of the photosynthetic system to reduce the loss due to photorespiration by producing a 4 carbon molecule to initially capture atmospheric CO 2

39 C-4 Plants The newly formed four carbon compound then is transported to bundle sheath cells and the CO 2 is released maintaining a high level of CO 2 in the bundle sheath cells for the C 3 cycle to occur and produce the precursors for sugar and starch synthesis.

40 C-4 Plants An added advantage of C 4 plants is that being more efficient they can tolerate having stomates being partially closed during periods of water stress

41 Calvin Cycle C 5 + CO 2 + ATP + NADPH C 6 H 12 O 6

42 Summary of Photosynthesis

43 Light H 2 O CO 2 Light Reaction NADPH & H + ATP Pi ADP Calvin Cycle NADP+ O 2 C 6 H 12 O 6 = Glucose

44 Water, Soil and Plant Nutrients