Presentation on theme: "Flowers. Basic structure of the angiosperm flower The fertilization process Pollen and stigma self-incompatibility Reproduction and diversity of angiosperms."— Presentation transcript:
Basic structure of the angiosperm flower The fertilization process Pollen and stigma self-incompatibility Reproduction and diversity of angiosperms The efficiency of animal pollination Some basic types of flower
Basic structure of the angiosperm flower
Collective nouns that can cause confusion! Calyx The outer whorl of a flower made up of sepals that are usually green, and protect the flower in bud. Carpel Bears the stigma, and frequently an elongated style, and encloses the ovules (sometimes gynaecium). The megasporophyll of the flower Ovary The total of the carpels in a flower is the ovary Corolla The collective term for the petals of a flower Perianth The floral envelope, it includes the calyx and corolla. Stamen The anther and its supporting filament. The microsporophyll of the flower Pistil Each separate carpel when there are lots of them in the ovary
Evolution of the pistil Ways in which Angiosperms are different from Gymnosperms Angio-Gymno 4 Ovules protected within an enclosed structure
… about meiosis, mitosis and cytokinesis?
Life cycle of angiosperms Fig
The fertilization process in Angiosperms (Equivalent to Fig 31.10)
Development of gametophytes
Angio-Gymno 5. Double fertilization to produce diploid zygote and triploid endosperm nucleus Ways in which Angiosperms are different from Gymnosperms
The triploid nucleus divides and the endosperm cell becomes a supercell with many nuclei and a milky consistency. Cyotkinesis forms membranes and walls between the nuclei and makes the endosperm more solid. The developing embryo uses the nutrients stored in the endosperm, as does the moncot seedling after germination. In most dicots, food reserves are moved to the cotyledons and the endosperm is not present in a mature seed. What goes on in the endosperm?
Somatic cell division involves two successive steps: mitosis and cytokinesis. In mitosis, the nuclear DNA duplicates and chromosomes segregates equally between the two daughter nuclei; cytokinesis divides these two nuclei and cytoplasm, including related cytoplasmic organelles, into two individual cells.
Angio-Gymno 5. Generally angiosperms have hermaphrodite flowers and cross pollinate (70%) Ways in which Angiosperms are different from Gymnosperms
… how many alleles there are at a locus?
Pollen and stigma incompatibility There can be dozens of alleles of the S-gene. If a pollen grain has an allele that matches an allele of the stigma upon which it lands, then the pollen tube fails to grow. What happens when pollen from plants with three different allele pairs is crossed with an S 1 S 2 plant? This system prevents self-fertilization AND fertilization from close relatives.
Rye grass incompatibility Pollen Grain Size and Surface Morphology in a Perennial Rye Grass Hybrid Stacey Lacoste Pollen grain on stigma Attempts to hybridize between particular varieties resulted in production of a web-like substance and incompatibility
The efficiency of animal pollination Lilium pollen Pollen is up to 30% protein Pollen is important for animals – and many animal pollinated plants do produce excess pollen. Animal pollination is targeted and so is more efficient than wind pollination. Animal pollinated flowers generally produce much less pollen than wind pollinated flowers. Generative cell Nucleus of tube cell
Some basic types of flower Separate petals Magnolia grandiflora
Flowers with a tubular corolla Gentiana algida Rocky Mountain National Park CO
A head with many florets
Monocotyledons Flower parts in threes Narcissus spp.
Oaks, have separate male and female flowers. The female flower (upper left) consists only of carpels and a calyx (collection of sepals). The male flowers are in elongated clusters, called catkins, and consist only of anthers and a calyx. Both sexes are found on the same tree, and thus oaks are monoecious (meaning same house). Some trees, e.g., poplars and willows are dioecious (meaning two houses), and there are male and female trees. Other monoecious genera include birch, walnut, ash, hickory, and most maples. Monoecious, wind pollinated
Reproduction and diversity of angiosperms Animal pollination is efficient and associated with the development of the hermaphrodite reproductive axis The diversity of flowers represent mechanisms promoting efficient pollination Prevention of self-fertilization maintains genetic variation by promoting cross pollination Sophistication of the reproductive process enables a large number of ways reproductive isolation can occur and so maintains genetic diversity
Sections you need to have read through and 31.9 and Courses that deal with this topic Botany 113 Plant identification and classification