Germination Plant Form Function 1 Primary Growth 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 Gibberellic Acid Gibberellin is hormone that supports seed germination When the radicle root emerges from the seed and begins to push into the ground germination is complete Bio 1B Instructor Carlson 1 Seedling is established when photosynthesis commences 2 Plant Hormones Chemical Communication Table 39 1 Germination Gibberellic Acid hormone supports seed germination Fig 39 11 Abscisic Acid ABA hormone inhibits seed germination and supports seed dormancy Fig 39 12 Abscisic Acid ABA Table 39 1 Supports seed dormancy Fig 39 12 Inhibits seed germination Fig 39 12 Inhibits growth stem elongation Closes stomata in response to water stress Counters the action of growth supporting hormones 3 4 Plant body organs tissues cells Tissue group of cells with a common structure and or function Organ several types of tissues that together carry out a particular function 5 6 Primary plant body morphology Campbell Figs 35 2 35 8 35 10 35 11 35 12 35 16 35 19 Lab manual Figs 4 1 4 2 4 3 4 4 4 5 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 7 8 Shoot Fig 35 2 35 8 35 11 35 12 35 16 Lab Manual Figs 4 1 4 3 Terminal bud with apical meristem Lateral buds axillary buds with meristems Node site of lateral buds on shoot Internode distance between two nodes 9 Plant Hormones Chemical Communication Table 39 1 Cytokinins Table 39 1 Promote cell division Promote lateral bud outgrowth Inhibit leaf senescence abscission 11 10 Plant Hormones Chemical Communication Table 39 1 Auxin indole acetic acid Campbell Table 39 1 Fig 39 9 Apical dominance by supporting activity of apical meristems Fig 39 9 Phototropism shoot growth Gravitropism root growth Stem cell elongation 12 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 Plant Hormones Chemical Communication Table 39 1 Brassinosteroids Table 39 1 Support elongation of pollen tubes Support elongation of stems Support growth of xylem Inhibit leaf abscission 13 Stem elongation supported by following hormones Gibberellic Acid Auxin Brassinosteroids 14 Stem elongation inhibited by following hormones Abscisic Acid Ethylene Fig 39 14 15 Plant Hormones Chemical Communication Table 39 1 16 Plant Hormones Chemical Communication Table 39 1 Abscisic Acid ABA Table 39 1 Inhibits growth stem elongation Supports seed dormancy Fig 39 12 Inhibits seed germination Closure of stomata in response to water stress Counters the action of growth supporting hormones 17 Ethylene Table 39 1 Promotes fruit ripening Promotes leaf abscission Fig 39 15 Promotes senescence Inhibits stem elongation Fig 39 13 14 Inhibits gravitropism 18 Shoot Fig 35 2 35 8 35 11 35 12 35 16 Lab Manual Figs 4 1 4 3 Terminal bud with apical meristem Lateral buds axillary buds with meristems Node site of lateral buds on shoot Internode distance between two nodes 19 20 21 22 23 24 Leaf Fig 35 2 35 5 35 6 35 7 35 8 35 18 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 Onion bulbs Fig 35 5 that we eat consist mainly of enlarged leaf bases that store food Wide variety of leaf shapes sizes in response different environments Leaf blade is primary site of photosynthesis 25 26 Leaf abscission causing leaf to fall off Promoted by ethylene Inhibited by brassinosteroids Inhibited by cytokinins 27 28 Modified leaves Fig 35 7 Tendrils modified leaf structures that wraps around adjacent stems other structures Spines the sharp spines on cacti are modified leaves the photosynthetic structure on cacti are the fleshy green stems Storage leaves some succulent plants have modified leaves for water storage Bulbs edible onion bulb Fig 35 5 consists mainly of enlarged leaf bases that store food Reproductive leaves some plants have leaves that produce adventitious plantlets which fall off the leaf and take root in the soil Bracts some plants have colorful modified leaves around flowers e g with poinsettia that serve to attract pollinators 29 30 Plant developmental plasticity influenced by genetic and environmental factors Plants have the ability to alter their form in response to local environmental conditions An example is the fanwort Cabomba caroliniana Fig 35 1 an aquatic angiosperm with feathery underwater leaves and pad like leaves that float on the surface of the water both leaf types have genetically identical cells however dissimilar environments result in the turning on or off of different genes during leaf development resulting in different morphology 31 Leaf Fig 35 2 35 6 35 7 35 8 35 18 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 32 Leaf Cuticle Cuticle Fig 35 18 matrix of crosslinked lipid molecules impregnated with extremely long chained lipids functions as a protective layer around the outside of the leaf 33 34 Photosynthesis Figs 10 3 10 7 10 10 Carbon Nutrient Acquisition Heterotrophs obtain carbon nutrients from other organisms animals fungi Autotrophs produce own carbon nutrients through photosynthesis green plants Fig 10a 10b 35 Occurs in chloroplasts in green plant tissues Leaf parenchyma cells Fig 35 10 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 36 Photosynthesis Equation 6CO2 12H2O light energy
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