Level 2 Plant Growth and Development Part I Toby Day MSU Extension Horticulture Associate Specialist

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1 Level 2 Plant Growth and Development Part I Toby Day MSU Extension Horticulture Associate Specialist Pages Montana Master Gardener Handbook

2 Plant Growth and Development Whole Plant Organs Tissues Cells Organelles Macromolecules

3 Inside the Plant Cell Chloroplasts Elongated organelle containing chlorophyll Site of photosynthesis Chlorophyll Uses light energy in photosynthesis Iron and magnesium is important

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5 Inside the Plant Cell Mitochondrion (mitochondria) Converts stored energy (glucose) into ATP Adenosine triphosphate ATP = energy currency that powers the cell s metabolic activities

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7 Inside the Plant Cell Cells are totipotent Totipotency is the ability of a single cell to divide and produce differentiated cells Differentiation Nucleus Processing and administrative center of the cell Controls cell functions Contains plant DNA

8 Inside the Plant Cell Vacuole Storage, waste disposal, protection, growth and pigments Important in providing structural support Structural importance of vacuole is its ability to control turgor pressure.

9 Turgor Pressure Dictates the rigidity of the cell Associated with Osmotic pressure Pressure required to prevent fluid diffusing through a semipermeable membrane Water With proper amounts of water, the vacuole swells creating high turgor pressure Lack of water: vacuoles shrink, reducing rigidity

10 Wilting

11 Inside the Plant Cell Cell Wall Thick rigid membrane that surrounds the cell Chemical signals, nutrients, water and cellular excretions are allowed to pass between cells (Plasmodesmata)

12 Cell Protection From Extreme Cold Water is moved out of the cell wall into the spaces between the cells so that ice crystals don t damage organelles

13 Cross Section of a Leaf Cuticle Waxy layer containing cutin Protects from water loss and pathogens Another reason for acclimating plants Why pesticides don t stick without surfactants

14 Cross Section of a Leaf Epidermis Closely packed cells Prevents water loss Barrier to fungi and other pathogens

15 Cross Section of a Leaf Mesophyll Specializes in photosynthesis Makes up the majority of the leaves Also stores energy and nutrients until transmitted to the veins and sent elsewhere

16 Cross Section of a Leaf Veins Contain the bundle sheath Phloem Xylem Cambium

17 Monocots vs. Dicots Cross Section View Monocots Dicots

18 Cross Section of a Leaf Stomata and Guard cells Guard cells open and close due to weather Regulate passage of water, O2, and CO2 in and out of the leaf

19 Role of Stomata Dawn light (blue) initiates the opening of the stomata

20 Respiration vs. Photosynthesis vs. Transpiration Photosynthesis Carbon dioxide + water = oxygen + sugar Respiration Sugar + oxygen = carbon dioxide + water + energy Transpiration Evaporation of water from plants Brings minerals and water up from the roots Cools the leaf 20

21 Questions?

22 Hormones A chemical released from one cell that affects growth and development of target cells which have appropriate receptors Auxins Gibberellins Cytokinins Abscisic acid Ethylene

23 Auxins Moves only downward from apical meristem Promotes growth by stimulating cell elongation Stimulates cell division Inhibits the growth of lateral buds Light amounts promote lateral roots (rooting hormones) Promotes flowering, fruit set and development of fruit Herbicides (2, 4-D) (auxin like)

24 Gibberellins Moves up and down vascular system Regulates height Too much = too tall Too little = dwarf plants Breaks dormancy (seeds) Can stimulate flowering in mature plants Promotes set of grapes and other fruits

25 Stimulate cell division in root meristem (where it occurs most often) Cytokinins Oppose auxin by movement upward and promoting growth of lateral buds Used in tissue culture Growth control in fruit Delays leaf aging and flower senescence Commercially used to prolong life of stored vegetables and cut flowers

26 Inhibits cell growth growth inhibitor Abscisic acid Helps prevent water loss by closing stomata Applied to nursery stock prior to shipping Keep them from wilting Accelerates abscission Stymies germination

27 Ethylene Gaseous hormone Produced in small quantities by fruit and vegetables Ripens fruit Synthetic Ethephon used to promote ripening on the tree Promotes abscission of leaves and fruit Degreen citrus

28 End