1Plant Form & Function #1,Primary GrowthBio 1BInstructor Carlson2GerminationGermination begins with the uptake of water by theseed which activates enzymes that breakdown storedproteins, lipids, and carbohydrates into smallermolecules to be used by growing regionsGibberellic Acid/Gibberellin is hormone that supportsseed germinationWhen the radicle (root) emerges from the seed and beginsto push into the ground, germination is completeSeedling is established when photosynthesiscommences3Germination• Gibberellic Acid hormone supportsseed germination (Fig 39.11)• Abscisic Acid (ABA) hormone inhibitsseed germination and supports seeddormancy (Fig 39.12)4Plant Hormones/ChemicalCommunication (Table 39.1)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 supportinghormones56Plant body:organs, tissues, & cells• Tissue: group of cells with acommon structure and/or function• Organ: several types of tissues thattogether carry out a particularfunction7Primary 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 thathave their own meristem at their tips and grow very muchlike the primary shoot axis8910Shoot(Fig 35.2, 35.8, 35.11, 35.12, 35.16, Lab Manual Figs 4.1, 4.3)Terminal bud with apical meristemLateral buds = axillary buds with meristemsNode: site of lateral buds on shootInternode: distance between two nodes11Plant Hormones/ChemicalCommunication (Table 39.1)Cytokinins (Table 39.1)• Promote cell division• Promote lateral bud outgrowth• Inhibit leaf senescence/abscission12Plant Hormones/ChemicalCommunication (Table 39.1)Auxin (indole acetic acid) (Campbell Table39.1, Fig 39.9)– Apical dominance by supportingactivity of apical meristems (Fig 39.9)– Phototropism (shoot growth)– Gravitropism (root growth)– Stem/cell elongation13Plant Hormones/ChemicalCommunication (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 fromthe fungus Gibberella fujikuroi, which is aplant pathogen on rice that resulted inunusually long shoots.14Plant Hormones/ChemicalCommunication (Table 39.1)Brassinosteroids (Table 39.1)• Support elongation of pollen tubes• Support elongation of stems• Support growth of xylem• Inhibit leaf abscission15Stem elongation supported byfollowing hormones:• Gibberellic Acid• Auxin• Brassinosteroids16Stem elongation inhibited byfollowing hormones:• Abscisic Acid• Ethylene (Fig 39.14)17Plant Hormones/ChemicalCommunication (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 waterstress– Counters the action of growth supportinghormones18Plant Hormones/ChemicalCommunication (Table 39.1)Ethylene (Table 39.1)– Promotes fruit ripening– Promotes leaf abscission (Fig. 39.15)– Promotes senescence– Inhibits stem elongation (Fig. 39.13-14)– Inhibits gravitropism19Shoot(Fig 35.2, 35.8, 35.11, 35.12, 35.16, Lab Manual Figs 4.1, 4.3)Terminal bud with apical meristemLateral buds = axillary buds with meristemsNode: site of lateral buds on shootInternode: distance between two nodes20212223242526Leaf(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 plantpart• Onion bulbs (Fig 35.5) that we eat consist mainlyof enlarged leaf bases that store food• Wide variety of leaf shapes & sizes in responsedifferent environments• Leaf blade is primary site of photosynthesis2728Leaf abscission causing leaf to fall off• Promoted by ethylene• Inhibited by brassinosteroids• Inhibited by cytokinins29Modified leaves (Fig 35.7)• Tendrils: modified leaf structures that wraps aroundadjacent stems & other structures• Spines: the sharp spines on cacti are modified leaves; thephotosynthetic structure on cacti are the fleshy green stems• Storage leaves: some succulent plants have modifiedleaves for water storage• Bulbs: edible onion bulb (Fig 35.5) consists mainly ofenlarged leaf bases that store food• Reproductive leaves: some plants have leaves thatproduce adventitious plantlets, which fall off the leaf andtake root in the soil• Bracts: some plants have colorful modified leaves aroundflowers (e.g., with poinsettia) that serve to attract pollinators3031Plant developmental plasticity influencedby genetic and environmental factors• Plants have the ability to alter their form inresponse to local environmental conditions• An example is the fanwort (Cabombacaroliniana Fig 35.1), an aquatic angiospermwith feathery underwater leaves and pad-likeleaves that float on the surface of the water;both leaf types have genetically identicalcells, however, dissimilar environments resultin the turning on or off of different genesduring leaf development resulting in differentmorphology32Leaf(Fig 35.2, 35.6, 35.7, 35.8, 35.18)Features of photosynthetic leaves:– epidermis (outer covering layer) consistsof specialized guard cells– internal parenchyma cells whichcompose main photosynthetic region– vascular tissue (“veins”) specialized fortransport of water & photosynthate33Leaf CuticleCuticle (Fig 35.18): matrix of cross-linked lipid molecules impregnatedwith extremely long-chained lipidsfunctions as a protective layeraround the outside of the leaf3435Carbon Nutrient AcquisitionHeterotrophs: obtain carbon nutrients fromother organisms– animals– fungiAutotrophs: produce own carbon nutrientsthrough photosynthesis– green plants (Fig 10a, 10b)36Photosynthesis (Figs 10.3, 10.7, 10.10)• Occurs in chloroplasts in green plant tissues• Leaf parenchyma cells (Fig 35.10) contain 40-50chloroplasts• Chlorophyll pigments in plants• convert
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