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PSU BIOL 240W - Big Picture/ Context

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BIOL 240W 1st Edition Lecture 14Outline of Last Lecture I. Asexual ReproductionII. Plant BreedingIII. Transgenic and Genetically Modified PlantsOutline of Current Lecture I. Big Picture/ ContextII. ReproductionIII. Life Cycle of PlantsIV. Plant Structure/function and ReproductionV. Asexual ReproductionVI. Selective BreedingVII. Genetically Modified OrganismsCurrent LectureI. Big Picture/ Contexta. There are millions of different species and organisms, and none of them are perfect. However, they are best adapted to their individual environmentsb. Organisms that can adapt pass on their beneficial traitsc. Keep in mind the pros/cons of asexual and sexual reproductiond. Plants are stuck where they are, so they cannot move during environmental changes or find a mate elsewhereII. Reproductiona. Sexual reproductioni. Situation where genes can be exchanged between two individuals1. Beneficial when there are changes in the environment2. Seeds produced remain dormant until favorable conditions are present3. CON- Energy must be used for seed germination, so this is a dilemmab. Asexual Reproductioni. Rapid colonizationii. Don’t need to worry about pollinationiii. CON- Catastrophic changes can cause an entire population to be wiped outIII. Life Cycle of PlantsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.a. Plants move back and forth between sporophyte and gametophyteb. We mostly see sporophytec. Capacity to produce haploid gametes that can be carried to next generationIV. Plant Structure/function and Reproductiona. Plants have female parts (carpels) and male parts (stamens)b. Structure and function go togetherc. Female parts and male parts in the same flower can be a problemi. Sex parts producing gametes close together may cause inbreeding, losing genetic diversityii. Plants must deal with thisd. Gametophyte developmentpollinationdouble fertilizationseed developmente. Development of embryo sacsi. Megasporangium produces megaspores, ultimately only one of megaspores survives. Mitotic divisions occur to make one big cell with eight haploid nuclei that get partitioned1. 1 egg cell2. 2 synergids3. 3 antipodal cells4. 2 polar nucleif. Development of pollen grainsi. Microsporangia form microspores. Consist of generative cell and tube cellii. Pollen grain consists of two-celled male gametophyte and the spore wallg. Pollinationi. Something must transfer pollen from anther to stigmaii. Rely on pollinator species, or wind (not as effective)1. Think about strategies, pros and cons of eachh. Fertilizationi. Pollen tube begins to grow when pollen lands on receptive stigma. Discharges two sperm cellsii. One sperm fertilizes egg (diploid zygote now) and the other combines with two polar nuclei (double fertilization, triploid)iii. Ovule-develops into seediv. Ovary-develops into fruiti. After fertilizationi. Endosperm development occurs first (triploid) mitotic divisions without cytokinesis1. Cytokinesis occurs after growthii. Endosperm, the large nutrient source, is used for developing seed. Sometimes, itdisappears completely and is taken up by cotyledons. Depends on individual speciesiii. Development of embryo1. First cell division is asymmetric- produces basal cell and a terminal cell2. Basal cell creates suspensor that anchors everything to parental tissue3. Terminal cell becomes most of the embryoa. Divides in the shape of a heart. “Bumps” on the heart turn into the cotyledons4. Meristems, which are rapidly growing stem cells, begin to develop and differentiateiv. Seed Maturation1. Sexual reproduction has its benefits, but now there is a seed and must rely that it will fall in a place where it can germinatea. Most of the time, the seed desiccates, becomes dormant, and waits for an ideal environment2. Garden bean- endosperm essentially gone, hypocotyl becomes stem, radicle becomes root, and cotyledons take over much of space3. Castor bean- some endosperm is left over, cotyledons have not completely taken over. (different strategies for different species)4. Monocot- single cotyledon filled with endosperm (maize seed/kernel)v. Dormancy1. Environmental cue triggers seed to germinate (long period of cold weather, fire, high temperatures, copious rainfall, digestion)2. Imbibition- uptake of water by dried seedsvi. Fruits1. Mature ovary of a flower2. Composition varies among species (fleshy, dry, etc)V. Asexual Reproductiona. Producing more plants, but just genetically identical clonesb. Successful with no changes in the environment; if there is a change, there is no diversityc. Fragmentation- part of plant is able to turn into full planti. Modify stem, root, etc.; whichever is successful in the certain environment (stolon, rhizome, roots)d. Apomixis- instead of just modifying stems/roots to grow a full plant, plants can asexually reproduce their seed without fertilizationi. Seeds are genetically identical to parentii. Take advantage of dispersaliii. Ex: dandelionse. Hermaphroditesi. Monoecious- plants with both male and female parts1. Inbreeding/self fertilization is a problem because no diversity is created (risky)2. To deal with this problem, the gametes can be separated spatially, one can develop before the other, or have a dioecious plant that is either male or femalef. Taking advantage of asexual reproductioni. Cultivation of sterile clones1. Ex: we produce bananas that do not make seedsii. Artificial asexual reproduction1. Grafting- taking one stock plant that donates the root system and fuse and scion to the stock root systemVI. Selective Breedinga. Choosing desired properties in offspringb. Breeding two individuals with different propertiesi. Must be interfertile, same species (or related), be able to produce viable offspring, and have variation between individualsc. However, traits good for agriculture that we like are bad for the plant’s survival (they may not have defense against pathogens)d. Ex: maize vs. teosinteVII. Genetically Modified Organismsa. Bacterial plasmids (small, circular DNA) is cut open with restriction enzyme, stick a gene in, then place it into cell of interestb. Crossing species barrier, because bacterial genes are expressed in plantsc. Ex: Bt soil bacterium has been used as a pesticide, but the Bt toxin can be inserted into plants so the protein is expressed and defend themselves against insectsd. Glyphosate destroys enzymes in plants.


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PSU BIOL 240W - Big Picture/ Context

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