Tropisms Growth responses to unidirectional stimuli Nastic Movements Growth responses to non-directional stimuli Seasonal Responses Photoperiodism, temperature (cold) treatments Light causes IAA To move to the dark side Type of light that causes phototropism Blue The pigment involved in phototropism Zeaxanthin In roots, these cells are responsible for detecting gravity Root cap cells These accumulate on lower side, more IAA accumulates as a result, which in turn inhibits cell elongation in roots Ca2+ ions In the presence of IAA, these on the lower surface produce enzymes which allow for increased cell elongation in stems mRNAs This is the touch response in plants Thigmotropism The touch response in plants is handled by these Special epidermal cells in tendrils Heliotropism Sun tracking These are good sun trackers Sunflowers The shaking response of plants is known as Seismonasty or Thigmonasty This includes movements of Venus Fly Trap and Sundew Seismonasty or Thigmonasty This is sometimes called "sleep movements" Nyctinasty This is caused by daily rhythms of light and dark Nyctinasty This includes movements of opening and closing of flowers Nyctinasty Elongation of the stem is influenced by the amount of shaking the plant experiences Thigomorphogenesis The Maryland Mammoth was a Huge tobacco plant The Maryland Mammoth led to study of this Photoperiodism Photoperiodism Length of day/night cycles Short-Day Plants Flower only if light period is shorter than critical photoperiod Long-Day Plants Flower only if light period is longer than critical photoperiod Day-Neutral Plants Flowering is not affected by photoperiod This light is how plants detect day/night cycles Red This is the receptor used by plants to detect day/night cycles Leaf This pigment is involved in plants ability to detect day/night cycles Phytochrome The elusive flowering hormone Florigen Seed germination in light-sensitive species is A phytochrome response Etiolation is A phytochrome response Cold treatment of seedlings Vernalization Soils vary widely as a result of these factors Climate and erosion, parent rock materials, living organisms, time O Horizon Surface litter layers, non-decomposed organic material A Horizon Major organic layer, dar in color, pH near 7; generally called topsoil B Horizon Larger particle size than A, accumulation of little organic matter, light in color; called the subsoil Topsoil A Horizon Subsoil B Horizon C Horizon Partially weathered bedrock In Omaha/Council Bluffs, we have these soils derived from wind-blown sediments Loess The best agricultural soils have a mixture of these three particles Sand, Silt, Clay The best agricultural soils are called Loam soil Clay particles are usually Negatively charged Gravitational water Fills largest pore spaces after a rain, but quickly drains from the soil Capillary water Fills intermediate pore spaces; primary source of water and minerals for the plant Field Capacity When soil is saturated at about 45% with capillary water Hygroscopic water Water bound to soil particles and unavailable to plants Three types of water Gravitational, capillary, hygroscopic Symplastic pathway Through cells and vacuoles from cell to cell; most cations follow this pathway Apoplastic pathway Through the cell walls and intercellular spaces (until it reaches the endodermis); most anions follow this pathway Plants not only need light, water, proper temperature, but they also need this from the soil Mineral nutrients These are needed in fairly large quantities by plants Macronutrients These are needed in very small quantities by plants Micronutrients Transpiration Loss of water from the plant This creates a "pull" force drawing water up the plant Transpiration "TAC" mechanism Transpiration, Adhesion, Cohesion When plants lose liquid water from the tips of leaves Guttation Guttation is caused by Root pressure With little transpiration, the root pressure pushes liquid water through special leaf structure called Hydathodes Guard cells have these, but other epidermal cells do not Chloroplasts In phloem, movement is from this to this Sources to Sinks