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Angiosperms -Are the most evolved and successful plants -Their life cycle has three unique features, all of which start with the letter f, fruits, flower, and double fertilization Flower Structure and Function -Flowers function in sexual reproduction -The four flower organs are sepals (asex), petals (asex), stamen (male), and carpel (femalepistals) -Stamens consist of two parts: Anther, which produces pollen and filament which holds it up -Carpels consist of three parts: --Ovaries: produces ovules (will become seeds) --Stigma: catches pollen grains --Style: Narrow tube connecting the stigma to the ovary -Pollen develops within the microsporangin of anthers -Ovules develop from megapores within the ovary Gamete Formation Pollination -Is the transfer of pollen from an anther ro a stigma -If pollination is successful, a pollen grain produces a pollen tube, which grows down into the ovary -The pollen tube is significant because it protects and delivers the sperm to the ovule, allowing angiosperms to reproduce outside of water Double Fertilization The Seed -When the pollen tube reaches the ovule, two fertilization events occur: -One sperm fertilizes the egg, forming the zygote, the zygote will develop into the embryo and eventually the new sporophyte plant -The other sperm combines with both polar nuclei, forming a triploid (3n) nucleus, this unique 3n tissue will give rise to the endosperm, a food-storing tissue in the seed -The union of two sperm cells forming both zygote and endosperm is unique to angiosperms -After double fertilization, the ovule develops into a seed and the ovary develops into the fruit, which encloses the seed -The seed coat protects the embryo and its food supply -A radicle is the embryonic root -The epicotyl consists of the shoot tip with a pair of miniature leaves Cotyledons -The food reserves of the endosperm are exported to structures termed cotyledons (monocotyledons have one and dicotyledons have 2) -Monocot: corn -Dicot: bean Seed Germination -As the seed matures, it enters dormancy, in which it has a low metabolic rate and its growth and development are suspended. The seed resumes growth when there are suitable environmental conditions for germination Steps to Seed Germation 1.Imbibes water 2.Breakdown food reserve (endosperm) 3.Start root cell division 4.Root spouts 5.Stem sprouts 6.Foliage leaves sprout Fruit form and Function -The fruit protects the enclosed seeds and aids in wind dispersal or in the attraction of seeddispersing animals Flowering Plants Reproduce -Sexual -Asexual -Both Asexual Reproduction -Models of asexual reproduction include fragmentation where detached vegetative fragments of some plant shoots can develop into whole offspring -The root system also give rise to many shoots that can become a separate shoot system, resuting in clones of the original plant -Agriculture uses several techniques of artificial vegetative reproduction such as grafting, growing clones from cuttings, and test tube clones to produce thousands of good variety clones Advantages of Asexual Reproduction -No need for a pollinator -Allows the plant to pass on all of its traits -Since clones usually arise from mature vegetative fragments of the plant, they receive genes that allow it to be well adapted to the same environment that allowed the parent plant to flourish Disadvantage of Asexual Reproduction -The genetic uniformity of a clone puts them at risk for extinction if there is a sudden change in the environment Advantage for Sexual Reproduction -Generates variation, allowing adaptations to change in the environment -Seed dormancy allows growth to be postponed until conditions are favorable -Seeds allow dispersal of offspring to more distant locations Disadvantages for Sexual Reproduction -Seedlings are usually fragile, making the production of enormous amounts of seeds necessary, using a large amount of the plant’s resources