Quiz 1 Study Guide

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Biological Sciences
BISC 366
Alison Kermode

Quiz 1 Revision five processes that occur during seed maturation (the seed expansion stage) that are important for the survival and longevity of seeds 1 - accumulation of food reserves - allows seedling to survive before beginning photosynthesis and autotrophic growth 2 - hardening of protective layers of seed coat → seed coat needed for mechanical support/structural protection, abiotic interactions, biotic interactions, chemical defense, protection, prevention of loss... 3 - mechanisms for dispersal develop (ie, seed morphology) 4 - intracellular synthesis of protective compounds → to withstand water loss, resistance to pathogens/insects/herbivores etc 5 - development of dormancy in some species → delay germination to distribute in time and space, require a signal to break dormancy, based on environmental conditions, may reduce offspring competition “Five Processes Done During Hardening” memory aid F - food reserves P- protective compounds D- dormancy D - dispersal H - hardening 1. What are the main steps of fertilization? Why is it called “dual fertilization?” main steps in fertilization: 1 - Pollen grain germinates after landing on stigma of correct spp. 2 - Tissues of style allow pollen tubes to grow through them easily 3 - Pollen tubes deep within style- callose plugs seal off protoplasm at the tip from the empty parts of the pollen tube 4 - Pollen tube reaches egg appara tus & enters one synergid 5 - Pollen tube tip bursts and releases both sperm cells (the sperm cells shred their protoplasm in synergid) 6 - One sperm cell nucleus unites w. egg cell nucleus = 2 n zygote nucleus (to form 2n embryo) 7 - Other sperm nucleus migrates from synergid into central cell; unites with both polar nuclei to establish a large endosperm nucleus (3n) dual fertilization: Pollen releases 2 sperm nuclei: 1) One sperm cell nucleus unites w. egg cell nucleus → 2 n zygote nucleus (will form 2n embryo) 2) Other sperm nucleus migrates from synergid into central cell; unites with both polar nuclei to establish a large endosperm nucleus (3 n) 3) Called double fertilization or dual fertilization: a. One sperm nucleus fuses with egg nucleus b. Other sperm nucleus fuses with polar nuclei Q: why 2 sperm nuclei?? microspore mother cell 1) undergoes meiosis = 4 1N pollen grains 2) ea undergoes mitosis = 4 x (1 generative cell fuses w egg, 1 vegetative cell forms pollen tube) Q: cells in ovary?? ovary contains = 1 egg cell, 2 synergids, 3 antipodals, 2 polar nuclei 2. What are the different forms of the embryo as development proceeds? see fig 16.4 from text: “embryo types” 5e, Plant Physiology memorize which different tissues cells differentiate to 1) Globular 2) Heart (2 mounds = outgrowth of cotyledons) 3) Torpedo (embryo root, cots and hypocotyl w xylem and phloem) 4) Mature embryo (shoot apical meristem) 3. What are the 3 main parts of a mature seed? 1 - embryonic root and shoot 2 - seed coat 3 - food reserve organs 4. What are the 3 different reserve organ types? - endosperm (resorbed, or live cells in dicots; dead cells in monocots) a. Non-embryonic tissue b. In cereals most of the food reserves are accumulated in the endosperm, which is not resorbed during seed development c. Endosperm cells are dead at seed maturity (monocot) - cotyledon (dicots) - megagametophyte (conifers) a. Haploid maternal tissue that becomes the major storage organ of the seed b. Conifers do not have an endosperm 5. What are the 3 stages of seed development? 1) Histodifferentiation a. Single celled zygote undergoes extensive mitotic division b. Cells differentiate to form the basic body plan of the embryo (axis and cotyledons) 1.Establishment of prospective dermal, ground and vascular tissues: radial pattern 2. Establishment of apical-basal polarity of embryo: persists throughout life of plant 3. Establishment of primary (root and shoot) apical meristems - RAM & SAM. Do not become active until after germination c. 3 N endosperm forms / 1N megagametophyte forms 2) Expansion/Maturation (5 steps of example Q) a. Cell expansion b. Seed protectants syn
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