Germination Germination begins with the uptake of water by the seed which activates enzymes that breakdown stored proteins lipids and carbohydrates into smaller molecules to be used by growing regions Plant Form Function Gibberellic Acid is a hormone hormone that supports seed germination Bio 1B Fall 07 Professor Carlson When the radicle root emerges from the seed and begins to push into the ground germination is complete 1 Seedling is established when photosynthesis commences 2 Germination Gibberrelic Acid hormone supports seed germination Abscisic Acid hormone inhibits seed germination and supports seed dormancy 3 Plant Hormones Chemical Communication Table 39 1 Primary plant body morphology Figs 35 2 35 8 35 10 35 11 35 12 35 15 35 18 35 29 Lab manual Figs 4 1 4 2 4 3 4 4 4 5 Auxin indole acetic acid Campbell Table 39 1 Fig 39 7 Apical dominance by supporting activity of apical meristems Phototropism shoot growth Gravitropism root growth Stem cell elongation Fig 39 8 Primary growth results in increase in length of stem axis Growth initiated at tips root shoot apical meristems Apical meristems at tips of shoots roots zones of high cell mitotic division activity new cell production Shoot apical meristems produce lateral appendages leaves axillary buds Axillary buds produce lateral shoots or branches that have their own meristem at their tips and grow very much like the primary shoot axis 4 5 6 Plant Hormones Chemical Communication Table 39 1 Gibberellic Acid Table 39 1 39 10 11 Seed germination Fig 39 11 Bud germination Stem elongation Flowering Fruiting Fig 39 10 Gibberellic Acid was originally isolated from the fungus Gibberella fujikuroi which is a plant pathogen on rice that resulted in unusually long shoots 7 8 9 10 11 12 Shoot Fig 35 2 35 8 35 10 35 11 35 15 Lab Manual Figs 4 1 4 3 Terminal bud Lateral buds Node site of lateral buds on shoot Internode distance between two nodes 13 Plant Hormones Chemical Communication Table 39 1 Cytokinins Table 39 1 Fig 39 9 Promote cell division lateral bud outgrowth Inhibit leaf senescence 15 14 Stem elongation supported by following hormones Gibberellic Acid Auxin Brassinosteroids 16 Stem elongation inhibited by following hormones Abscisic Acid Ethylene 17 18 Leaf Leaf Abscision Fig 35 2 35 5b 35 6 35 7 35 8 35 17 35 29 Leaf Blade with petiole leaf stalk Celery the petiole is the edible plant part Lettuce the blade of the leaf is the edible plant part Wide variety of leaf shapes sizes in response different environments Leaf blade is primary site of photosynthesis Promoted by ethylene Inhibited by brassinosteroids 19 20 Leaf Fig 35 2 35 5b 35 6 35 7 35 8 35 17 35 29 Features of photosynthetic leaves epidermis outer covering layer consists of specialized guard cells internal parenchyma cells which compose main photosynthetic region vascular tissue veins specialized for transport of water photosynthate 21 22 23 24 Leaf Cuticle Cuticle Fig 35 17 matrix of cross linked lipid molecules impregnated with extremely long chained lipids functions as a protective layer around the outside of the leaf Photosynthesis Figs 10 3 10 10 page 183 Nutrient Acquisition Heterotrophs obtain nutrients from other organisms animals fungi Autotrophs produce own food through photosynthesis green plants 25 Occurs in chloroplasts in green plant tissues Leaf parenchyma cells contain 40 50 chloroplasts Chlorophyll pigments in plants convert energy from sunlight to chemical energy in the form of ATP NADPH an electron carrier Carotenoids carotene and xanthophylls absorb wavelengths of light that are not absorbed by chlorophyll and extend the range of wavelengths that can drive photosynthesis 26 Photosynthesis Equation 6CO2 12H2O light energy C6H12O6 glucose 6O2 6H2 27 28 29 30 Photosynthesis Equation 6CO2 12H2O light energy C6H12O6 6O2 6H2O C6H12O6 glucose Simplest Form of Photosynthesis Equation CO2 H2O light energy CH2O O2 H2O Light dependent reactions Light energy H2O chemical energy ATP NADPH O2 oxygen in O2 derived from oxygen in H2O Light independent reactions Calvin Cycle Chemical energy ATP NADPH CO2 CH2O Carbon in sugar is derived from carbon in CO2 Gas exchange between atmosphere and plant via stomata in leaves Stoma stomata plural guard cells pores Fig 10 3 Guard cells pair of bean shaped cells Pore opening between guard cells Abscisic Acid ABA causes stomata to close during times of low water availability 31 Gas exchange between atmosphere plant via stomata in leaves 32 CO2 in Atmosphere Global Warming O2 produced by plant released out of stomata pores into atmosphere where it is available for humans animals to breath fossil fuel burning deforestation in past 100 years atmospheric CO2 H2O released out of the pores via evapo transpiration atmospheric CO2 contributes to global warming in some species e g coastal redwoods Douglas Firs during high fog conditions H2O can be absorbed from the air into the leaf through the stomata pores to provide H2O for the plant Photosynthesis by green plants removes CO2 from the atmosphere sequesters carbon in wood During photosynthesis when CO2 levels within leaf fall below optimal levels the stomata open CO2 diffuses in from 33 atmosphere 34 Sugar produced by photosynthetic organisms fuels cellular respiration and growth of plant sugars are typically stored in the form of starch long chains of glucose molecules transported in the form of the disaccharide sucrose glucose attached to fructose or monosaccharide glucose or fructose Photosynthetic organisms are eaten by animals and fungi Directly or indirectly many organisms get their energy from photosynthesis 35 36 Plant Pigments Photosynthesis Plant Pigments Photosynthesis Carotenoids Carotenes e g beta carotene in carrots lycopene in tomatoes Xanthophylls e g zeaxanthin which gives corn yellow color 37 Plant Pigments Photosynthesis During most of year the carotenoids are not visible in the leaves because the chlorophyll pigments cover them up Carotenoids in chloroplasts extend range of wavelengths that drive photosynthesis protect chlorophyll by acting as anti oxidant and destroy free radicals that damage the chlorophyll molecules beta carotene also works a beneficial anti oxidant in humans 38 Flavonoid Pigment as Plant Suncreen Flavonoids absorb ultraviolet radiation which protects leaves stems from damaging effects of UV In fall as the deciduous leaves are beginning to die chlorophyll degenerates and the red orange and yellow carotenoids become visible functions as a
View Full Document
Unlocking...