BIOL 152 1st Edition Lecture 12 Outline of Last Lecture I Summary of plant transport systems a Water nutrients b Bulk flow II The move to land a Preventing desiccation b Confronting gravity c Exploring complex habitats III Alteration of generations a Generic b Humans IV Diploid haploid organisms V Plant life cycle summary a Examples VI Gymnosperms a Homospory b Heterospory Outline of Current Lecture I Reproduction in gymnosperms and angiosperms a Homologous structures b Similarities and differences c Flowering plant apomorphies II How apical meristems work a Indeterminate growth b Tunica and corpus layers c Maturation of cells and tissues III Origin of flowers a Change to determinate growth b Control of call fates i Position effects ii Genetic influence 1 ABC model of flower genetics IV Plants respond to light a Discovery of plant hormones i Auxin 1 Charles and Francis Darwin These 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 Went ii Produced by stem tip iii Influences plant growth Current Lecture General 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 stamen Female cones are homologous to carpel Essential flower organs Anther microsporangium o Forms microspores by meiosis o Microspores pollen Carpel contains megasporangium o Forms megaspores by meiosis o Holds ovules Site of fertilization Mature to become seeds How do seeds become mature plants THE MERISTEM The process morphogenesis o The development from zygote to adult ontogeny Determinate vs Indeterminate growth Most animals determinate o They reach a certain point and stop growing Most plants intermediate o Constant growth Physical Constraints and Forces Plants cells locked in place o Cellulose wall does not allow for much movement Cell division and elongation yield growth o Turgor pressure Apical Meristem Tunica one set of layers Corpus division planes random mitosis occurs Fate of cell lineages set near meristem Epidermis at surface of tunica o First called protoderm Procambial strand now called vascular tissue SUMMARY OF APICAL MERISTEM Site of cell division o Ultimate source of all plant cells Distinctive layers o Tunica differentiating layers o Corpus maintains active mitosis Forms precursors of mature tissues o Procambium vascular tissue o Protoderm epidermis Vegetative growth is modular One module stem axillary bud leaf Whole plants repeated modules Growth is indeterminate Flower Development Compressed shoots o Internodes short Change to determinate growth How do cells initiate floral parts Combination of cell position and genetics Control of flower development Genetic influence Mutants demonstrate genetic control Arabidopsis experimental system o 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 Outer inner sepals carpels o Genetics Genes control trait expression Control of Plant Growth Plant responses Phototropism o Response to light Gravitropism o Response to gravity Photoperiodism o Response to changing seasons Mechanisms 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 tip o Exposure of tip to light is necessary o Lower stem region does not control tip response o Response mediated by a diffusible substance
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