Hormones• Hormones are chemical substances that control a plant’s patterns of growth, development, and responses to environment conditions• Auxins are produced in the apical meristem and are transported downward into the rest of the plant, stimulates cell elongation
Cont.• Auxins are responsible for the plant response called gravitropsim and phototropism• Auxins are also responsible for lateral buds (branches)• Cytokinins are plant hormones that stimulate cell division and the growth of lateral buds and cause dormant seeds to sprout
Cont.• Gibberelinns cause an increase in overall size of plants and individual plant structures• Ethylene is produced in response to auxins, fruit tissue release small amounts of the hormone which stimulates fruit to ripen
Plant Response• Tropism – response to external stimuli• 3 types:• Gravitropism – responds to force of gravity• Phototropism: response to light• Thignotropism: response to touch
Cont.• Photoperiodism: seasonal activity like flowering and growth (phytochrome is plant pigment responsible)• Dormancy: in winter, deciduous plants turn off photosynthetic pathways, transport materials from leaves to roots, and seal leaves off from the rest of the plant
Plant Adaptations• Aquatic plants: for sufficient oxygen absorption, aquatic plants have tissues with large air-filled spaces through which oxygen can diffuse• Desert: extensive root systems, reduces leaves, thick stems that can store water (xerophytes)
Cont.• Nutritional specialists: specialized features for obtaining nutrients (carnivorous or parasites)• Chemical: manufacture compounds that are toxic to predators
A particular slide catching your eye?
Clipping is a handy way to collect important slides you want to go back to later.