plant hormone

• Phototropism - plant growth response to light
• shoots bend toward light - positive phototropism roots
• bend away from light - negative phototropism
• Gravitropism - plant growth response to gravity
• shoots bend away from gravity – negative gravitropism

  mediated by auxin - causes lower side of stem to elongate
• shoots bend away from gravity – negative gravitropism

  mediated by auxin - causes lower side of stem to elongate
• roots grow toward gravity - positive gravitropism

  mediated by gravity sensing cells in root cap
• Thigmotropism - plant growth response to touch causes coiling of tendrils mediated by auxin and ethylene
• Turgor is pressure within a living cell resulting from water diffusion.
• pulvini - multicellular swellings located at base of each leaf or leaflet
• After exposure to a stimulus, changes in leaf orientation are mostly associated with rapid Turgor pressure changes in pulvini
• Circardian Clocks -are endogenous timekeepers that keep plant responses synchronized with the environment
• Photoperiodism - plant responses to day and/or night length
• plant hormones are endogenous organic compounds active at very low concentration,