BIOL 152 1st Edition Lecture 12 Outline of Last Lecture I. Summary of plant transport systemsa. Water/nutrientsb. Bulk flowII. The move to landa. Preventing desiccationb. Confronting gravityc. Exploring complex habitatsIII. Alteration of generationsa. Genericb. HumansIV. Diploid/haploid organismsV. Plant life cycle summarya. ExamplesVI. Gymnosperms a. Homosporyb. Heterospory Outline of Current Lecture I. Reproduction in gymnosperms and angiospermsa. Homologous structuresb. Similarities and differencesc. Flowering plant apomorphiesII. How apical meristems worka. Indeterminate growthb. Tunica and corpus layersc. Maturation of cells and tissuesIII. Origin of flowersa. Change to determinate growthb. Control of call fatesi. Position effectsii. Genetic influence1. ABC model of flower geneticsIV. Plants respond to lighta. Discovery of plant hormonesi. Auxin1. Charles and Francis DarwinThese 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.2. Boysen-Jensen and Fritz Wentii. Produced by stem tipiii. Influences plant growthCurrent LectureGeneral functions of flower structure- Sepals- protect developing bud- Petals- attract pollinators- Filaments- hold anthers- Anthers- produce pollen- Stigma- sight of pollen deposition- Style- runway for pollen tubes- Ovary- holds ovules; matures to become “fruit”Male cones and microsporangia are homologous to stamenFemale cones are homologous to carpel“Essential” flower organs- Anther=microsporangium o Forms microspores by meiosiso Microspores= pollen- Carpel contains megasporangiumo Forms megaspores by meiosiso Holds ovules Site of fertilization Mature to become seedsHow do seeds become mature plants?THE MERISTEM.- The process: morphogenesiso The development from zygote to adult: ontogenyDeterminate vs. Indeterminate growth- Most animals= determinateo They reach a certain point and stop growing- Most plants= intermediateo Constant growthPhysical Constraints and Forces- Plants cells “locked” in place o Cellulose wall does not allow for much movement- Cell division and elongation yield growtho Turgor pressureApical Meristem- Tunica- one set of layers- Corpus- division planes random (mitosis occurs)Fate of cell lineages set near meristem- Epidermis at surface of tunicao First called protoderm- Procambial strand now called vascular tissueSUMMARY OF APICAL MERISTEM- Site of cell division o Ultimate source of all plant cells- Distinctive layerso Tunica- differentiating layerso Corpus- maintains active mitosis- Forms precursors of mature tissueso Procambium vascular tissueo Protoderm epidermisVegetative growth is modular- One module= stem + axillary bud + leaf- Whole plants= repeated modules- Growth is indeterminateFlower Development- Compressed shootso Internodes short- Change to determinate growthHow do cells initiate floral parts?- Combination of cell position and geneticsControl of flower development- Genetic influence- Mutants demonstrate genetic control- Arabidopsis- experimental systemo ABC model, if one gene (say, A) was blocked, the resulting flower would be affected due to it one being able to express gene B and C- Indeterminate determinate- Internodes very short- Cell fate governed by:o Position Outerinner = sepals carpelso Genetics Genes control trait expressionControl of Plant GrowthPlant responses- Phototropismo Response to light- Gravitropismo Response to gravity- Photoperiodismo Response to changing seasonsMechanisms of phototropism- Plants grow towards light!o Why are shaded cells longer? Darwin hypothesized that substances formed at the shoot tip influence cell elongation- Conclusions:o Phototropism controlled by stem tipo Exposure of tip to light is necessaryo Lower stem region does not control tip responseo Response mediated by a diffusible
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