plant chemical regulation - plant hormones have multiple functions, unlike that of animals
- auxin - made in apical meristem
- if lacking, plant will no longer grow towards light
- promotes stem, vascular tissue, root growth
- suppresses lateral bud growth, leaf abscission
- “agent orange” - derived from auxin to speed up growth, make trees age faster
- cytokinins - stimulates cell division, differentiation
- promotes lateral growth
- gibberellins - synthesized from leaves
- apical growth, stimulates protein synthesis
- ethylene - gaseous
- drops damaged leaves when in contact w/ toxin
- ripens fruit
- abscissic acid - controls stomata opening
- stimulates winter dormancy
tropisms - positive/negative growth toward external stimuli
- photoperiodism - response to light
- lets plant know what time of year it is
- bright red light >> Pr converts to Pfr phytochrome>> inhibits flower growth
- far red light (longer wavelength) >> Pfr converts to Pr phytochrome>> no more flower inhibition
- gravitropism (geotropism) - response to gravity
- thigmotropism - vines curling around objects
- etoliated plant - grown in the dark
- loses chlorophyll >> becomes white
- acts as fiber optics >> grows longer
parts of early plant -
- coleoptile - in grass, 1st leaf sheath
- epicotyl - apical end of embryo
- hypocotyl - between radicle and leaves
- mesocotyl - embryonic stem axis
dicot germination - hypocotyl emerges in an arch
- 2 cotyledons protect plumule (embryonic leaves) as it emerges
- light >> hypocotyl arch straightens out
- cotyledons start photosynthesis, later drop off
monocot germination - has sharp primary leaf
- coleoptile acts as needle to penetrate ground
Subject:
Subject X2:
