Biology: Feb. 8-12
Biology: Feb. 8-12 Biology 1120-001
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This 2 page Class Notes was uploaded by Anzlee on Friday February 12, 2016. The Class Notes belongs to Biology 1120-001 at Middle Tennessee State University taught by Andrew Brower in Spring 2016. Since its upload, it has received 20 views. For similar materials see Biology in Biology at Middle Tennessee State University.
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Date Created: 02/12/16
Biology: February 8-12 Types of Plants Based on Consumption • Parasitic plants- tap into vascular tissue of the host to receive nutrients • Carnivorous plants- receive nitrogen directly from other organisms, ex. pitcher plants • Epiphytes- commensal with fellow plants, meaning both plants benefit Sensory System in Plants • can sense: light, gravity, touch, parasites, etc. • respond by: change in growth, cellular activity, and genetic expressions (response to stimuli: tropism) • Light: o Phototropism/photomorphogenesis o plants respond particularly to blue light (not to green light) o the stomata responds as well as the growth pattern o auxin is the hormone responsible for this tropism (cells at the tip of the plant senses and sends a signal to create the response) o can sense shade because there are different wavelengths (full sunlight has an equal ratio of far red light to red light while shade has more far red light which acts as an inhibitor and can trigger photomorphogenesis); plants can sense when there are plants crowding them, so they will produce thin long stems to elongate o etiolation- white stems grow to elongate instead of produce chlorophyll; once in sunlight, chlorophyll will be produced • Gravity o Gravitropism o shoots grow up, roots grow down o auxin on the lower side of the stem has a higher concentration to allow the plants to grow up against gravity; meristematic cells in root cap sense gravity • Touch o Thigmotrophism o directional growth; not rapid; example- response to wind would allow them to not grow as tall and have a thicker stem o nutation- slowly swing around so they can find something to wrap around o plants move rapidly through: charges created from action potentials of water/nutrients passing through membranes; turgor pressure • Other tropisms: electrotropism (electricity), chemotropism (chemicals), thermotropism (temperature), etc. • Sensing Time/Day and Night o flower opening and closing o leaf folding/unfolding o scent production Dormancy • have the ability to cease growth and become dormant to survive • protection from freezing, drought, and heat shock • allow better chance of seed survival as well to spread genes Chemical Signals in Plants • plant hormones are involved in internal signaling processes • 7 categories: o auxin- mediates phototrophic response (promotes bending and elongation), increases plasticity of cells, mediates gravitopic response which allows roots to grow downwards (inhibits cell elongation) o gibberellins- responsible for elongation of stems, hasten seed germination o abscisic acid- induces dormancy, suppresses bud growth, opens and closes stomata (opposite of gibberellins) o cytokinins- help cell division and differentiation; most in root apical meristem; pathogens/bacteria can cause this to be overproduces which leads to large growths on the plants called a “crown gall” o brassinosteroids- broad spectrum of effects; triggered by environment o ethylene- helps fruit development/ripening and leaf and flower senescence; can be manipulated to delay ripening Plants are Affected Negatively by: • Herbivores • Nematodes • Fungal Spores • Pathogenic fungi • Bacteria and viruses • Mites • Insects (ex. wood, leaf, fruit boring insects) Plants Fight Back • Allelopathy- plant vs. plant: slow growth or block seed germination • Forms of offense: thorns, spines, sap, latex, chemical toxins • Antagonistic coevolution: evolution of chemical and physical deterrents • Systemin- hormone produced by damaged cells, which then binds to undamaged cells which then produce jasmonic acid • Jasmonic acid acts as a defense and ‘distress call’ • Pathogen-Specific Response: o Hypertensive response- response to invader: rapid death around site o Systematic acquired response- prepares for future attacks (allows it to respond quicker in the future)
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