Plsc 101 Week Two Notes
Plsc 101 Week Two Notes plsc 101
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This 8 page Class Notes was uploaded by randomchic12 on Friday March 25, 2016. The Class Notes belongs to plsc 101 at Louisiana Tech University taught by Dr. Paul Jackson in Spring 2016. Since its upload, it has received 29 views. For similar materials see plant science in Botany at Louisiana Tech University.
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Date Created: 03/25/16
1 Plsc 101 Week Two Notes Exam 1 Material (cont.) Crop & Botanical Classification Crop Plant Classification Botanical Classification taxonomy the science of classification of organisms botanical ranks “for plants”: kingdom, division, class, order (end in “ales”), family (end in “aceae”), genus, species, variety, cultivar binomial nomenclature= genus and species ex: maize/corn (common) & Zea mays L (scientific) ex: Loblolly pine (common) & Pinus taeda L (scientific) Authority who named the plant ex: L= Linneaus variety plants of same species but display differences in nature; differences breed true Ex: Acer saccharum var. leucoderme Genus species variety variety name sugar maple more heat tolerant (SE US) cultivar selected variety propagated for desirable attribute; does not breed true if breeding stopped, cultivar would disappear some are patented & cost more ex: Cornus florida ‘Big Giant’ (Big Giant cultivar) flowering dogwood with large white flowers Cornus florida var. rubra ‘Cherokee Brave’ Variety= pink to pinkish red flowers cultivar= reddish pink with white center angiosperm produce seed within fruit via ovary & ovule in a flower (flowering plants) gymnosperms produce seeds in cones (lack fruit), nonflowering plants 2 ex: conifers (pine, fir, spruce, cypress) *Subclass of Angiosperms Monocotyledon (monocot) has one cotyledon (seed leaf) from seed ex: all grasses, corn, tulips, orchids, lilies, irises Dicotyledon (dicot) has cotyledons (seed leaves) from seed ex: legumes, cotton, tomato, sweet potato, most trees and shrubs other differences include: numbers of flower parts, leaf vein patterns, root structures, & response to herbicides (physiology) Length of life annual plant completes life cycle in one growing season ex: corn, beans, marigolds biennial completes life cycle in two growing seasons season 1: produces vegetative growth season 2: produces flowers and seeds to reproduce ex: cabbage, beets, celery, carrots, onions perennial can grow for many years some dieback in winter and regrow in spring from stored food in roots (legumes & grasses) some enter a dormant period (trees & shrubs) Agronomic Crop Classification cereals or grains grasses grown for their edible seeds 75% starch; 12% protein; 2% fat ex: wheat, corn, barley, rice, sorghum legumes (pulses) high protein seed produced in pods 1/3 dry wt. as protein 3 ex: peanut, field bean, field pea, soybean, lima bean forage crops fresh or preserved vegetative matter used as feed for animals ex: grasses and clover used for hay root crops grown for their enlarged roots ex: sugarbeet, carrot, turnip, sweet potato fiber crops grown for fiber to make paper, cloth, or rope ex: cotton, flax, hemp sugar crops grown for extraction and crystallization of their sweet juice ex: sugarbeet and sugarcane (sucrose); corn and grain sorghum (dextrose) oil crops seeds with useful oils ex: flax, soybean, peanut, sunflower, sesame tuber crops a short, thick underground stem; stores food reserves; not a root ex: potato and Jerusalem artichoke drug crops seeds with useful oils ex: tobacco, mint, pyrethrum ornamental crops plants grown for their esthetic value ex: flowers, shrubs, trees, ground cover, turf grass forest tree seedlings grown for reforestation of lands and used in landscape ex: conifers (pines, cypress); hardwoods (oaks, hickory, maple) Special Purpose Classification cover crops help manage soil fertility, moisture, and erosion; can help control weeds, pests, and diseases ex: sorghum sudangrass in a forest nursery maintain soil characteristics; cover up land to protect it for future plants silage crops preserved succulent by partial fermentation in a tight space; 5080% moisture companion crops crops grown with another crop small grain seeded with a legume for erosion & weed control one crop can provide income if other one fails 4 Seeds Seed Content seeds store food for germination as: fat, oil, or carbohydrates (megagametophyte or endosperm) seeds with high fat and oil content = higher in protein example: cottonseed for cattle feed embryo contains: cotyledon embryonic or seed leaf; third to emerge hypocotyl embryonic stem; means “below seed leaf”; second to emerge epicotyl embryonic shoot; above cotyledons; fourth to emerge radicle embryonic root; first to emerge from seed Seed Germination (germ) process of plant emerging from a seed and beginning growth external conditions required for germ: supply of moisture (imbibing) supply of oxygen suitable temperature certain light conditions a deficiency in any factor may prevent germination moisture: water is critical for rapid germ applied to seed or absorbed from soil germ occurs when moisture content of most field crop seeds reach 2675% examples: 5 sorghum & millet = 26% moisture content small grains = 4550 % moisture content soybean = 75 % moisture content oxygen: required for respiration during germ dry seeds can be impervious to O 2 seed must absorb water first, then O 2 seeds planted too deep or in saturated soil may not germinate = oxygen deficiency temperature: germ can occur with wide range of temps depends on crop examples: ryegrass= 41 F or less corn minimum temp for germ = 50 F light: seeds requiring more light planted closer to surface if small seeds germ too deep in soil = loss of food supply before cotyledon reaches surface We know what is needed, so how does it work? water imbibed to certain % of seed dry weight seed coats soften & seeds swell up food reserves (fats, oils, carbs, sugars) go in to solution & transported to growing points respiration provides energy for all germ processes respiration occurs faster in moist seeds vs. dry seed energy consumed during germ = ½ the weight of dry seed growing (swelling) embryo ruptures seed coat radicle is first to emerge (when radicle emerges seed is germinated) 6 at this point, seed has absorbed all available water now, radicle absorbs water needed for seedling growth Seed Quality some seeds are empty & have no embryo broken or injured seeds can have: reduced germination higher seedling mortality (more deaths) smaller plants seeds can mold in certain conditions (too wet, certain temp) fungi and bacteria can absorb seed’s nutrients seeds are often treated with fungicides hyphae fungal body; extension mycelium collection of hyphae dampingoff seeds do not germinate or young seedlings are killed from pathogen infection pathogen absorbs seed material = no germ if germ, then hypocotyl constricts and seedling buckles seedling death Seed Dormancy when mature, healthy, and imbibed seed fail to germ when in favorable conditions for germ seed stays dormant until conditions are favorable for germ (temp, light, water, etc.) Why? to prevent germ while on parent pant to protect seed from harsh weather (cold winters) to ensure space and light for growth the seed wants to be in a situation for successful growth 7 mechanisms of seed dormancy & how to break it physical mechanism: hard seed coats prevent water & oxygen absorption soak in water for period pass through animal gut fire stratification or “moist chilling” (done for conifer seed) soaked in water for a few hours then chilled in refrigerator for days physiological mechanism: immature embryo is maintained until right temps (for example) are met then embryo ripens prior to germ (known as afterripening) Seed Testing seed is expensive = growers want good seed laboratory seed testing determines: germination % # pure seed seed mixed with other seeds any weed seeds present *side note: seed efficiency # of plantable seedlings from a certain # of pure live seed results help with decisions of: seed selected seeding rates based on germ % combating weed problems Exam 2 Material: Botany of Crop Plants Nature of Crop Plants Life cycle of crop plants spermatophyte seed plant; most crop plants reproduce by seed 1.) seed germination 2.) produces a seedling 8 3.) vegetative phase increases in number & size of roots, stems, & leaves 4.) reproductive phase plants flower and produce seeds Plant Morphology Roots root functions: anchors plant absorption of water and nutrients (i.e. nitrogen) physical support for aboveground tissue food storage organ radicle embryonic or primary root two types of root systems: fibrous many slender roots similar in diameter and length (monocots) ex: cereals, grasses taproot main root that pushes straight downward with lateral roots branching throughout its length (dicots) ex: legumes, root crops, woody plants absorption by roots root hairs increase root surface area hairs help absorb water and nutrients nutrient absorption is independent of water needs roots grow in moist soil but not saturated soils saturated soils = anaerobic conditions absence of oxygen = roots smother and die
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