Flowers Basic structure of the angiosperm flower The fertilization process Pollen and stigma self-incompatibility The efficiency of animal pollination Some basic types of flower Reproduction and diversity of angiosperms Basic structure of the angiosperm flower
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The fertilization process
Pollen and stigma self-incompatibility
The efficiency of animal pollination
Some basic types of flower
Reproduction and diversity of angiosperms
The outer whorl of a flower made up of sepals that are usually green, and protect the flower in bud.
Bears the stigma, and frequently an elongated style, and encloses the ovules (sometimes gynaecium). The megasporophyll of the flower
The collective term for the petals of a flower
The total of the carpels in a flower is the ovary
The floral envelope, it includes the calyx and corolla.
Each separate carpel when there are lots of them in the ovary
The anther and its supporting filament. The microsporophyll of the flower
Ways in which Angiosperms are different from Gymnosperms
Angio-Gymno 4 Ovules protected within an enclosed structure
(Equivalent to Fig 31.10)
Angio-Gymno 5. Double fertilization to produce diploid zygote and triploid endosperm nucleus
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.
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.
Ways in which Angiosperms are different from Gymnosperms and cytokinesis.
Angio-Gymno 5. Generally angiosperms have hermaphrodite flowers and cross pollinate (70%)
… how many alleles there are at a locus? and cytokinesis.
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 S1S2 plant? This system prevents self-fertilization AND fertilization from close relatives.
Pollen Grain Size and Surface Morphology in a Perennial Rye Grass Hybrid
Attempts to hybridize between particular varieties resulted in production of a web-like substance and incompatibility
Pollen grain on stigma
Pollen is up to 30% protein
Nucleus of tube cell
Animal pollination is targeted and so is more efficient than wind pollination.
Animal pollinated flowers generally produce much less pollen than wind pollinated flowers.
Pollen is important for animals – and many animal pollinated plants do produce excess pollen.
Rocky Mountain National Park CO
Flower parts in threes
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.
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 and cytokinesis.
17.10 through 17.14 and 31.9 and 31.10
Courses that deal with this topic
Botany 113 Plant identification and classification