Plant Reproduction and Plant Diversity II Chapter 30/38

Seed plants - vascular plants that produce seeds. 3 adaptations that seed plants have: 1 Gametophyte more reduced. 2 Seed evolved. 3 Pollen evolved.

Gametophytes of seed plants almost invisible. Gametophytes still exist - plants can destroy themselves at this stage if there something wrong with plant.

Seed - sporophyte embryo packaged with food supply within protective coat. Seed plants produce 2 different types of sporangia - produce 2 different types of spores: megaspores (female gametophyte) and microspores. Gametophytes stay in sporophyte as it develops.

Ovule - integuments (part protective covering), megaspore, and megasporangium. Female gametophyte develops inside megaspore; produces 1 + egg cells. Fertilized egg develops into sporophyte embryo. Whole ovule develops into seed.

Microspores (pollen) – light, carried through air. Pollen will create pollen tube - allow sperm to travel down into female gametophyte. 2 groups of seed plants: gymnosperms and angiosperms.

Gymnosperms 4 phyla of gymnosperms still around. Phylum Ginkgophyta contains only Ginkgo biloba.

Phylum Cycadophyta - cycads - look like palm trees. Phylum Gnetophyta - 3 different types of plants (ephedra) Phylum Coniferophyta - largest phyla - conifers - from reproductive structure, cone.

Conifers Conifers are evergreen - keep leaves all year long. Needles help in dry conditions. Conifers include pines, firs, spruces, larches, yews, junipers, cedars, cypresses, and redwoods.

Life cycle of gymnosperms Conifers - heterosporous (develop male and female gametophytes) Produce pollen cones and ovule cones. During pollination, pollen falls on ovule. Creates pollen tube that digests through megaspore.

Megaspore, now fertilized, goes through meiosis to produce 4 haploid cells. 1 cell turns into female gametophyte, others (archegonia) will develop within gametophyte.

Angiosperms Angiosperms - flowering plants - produce flowers, fruit. Phylum Anthophyta - all angiosperms. Divided into 2 groups: monocots and dicots. Monocots - leaves with parallel veins, dicots have netlike venation.

Angiosperms - long tracheids - help transport water, support plant. Flower specialized for reproduction. Most angiosperms rely on pollination through animals; grasses - random chance.

Flower - specialized shoot - 4 circles of modified leaves: sepals, petals, stamens, and carpals. Sepals - base of flower - modified leaves that enclose flower before it opens. Petals lie inside ring of sepals - usually colorful in animal pollinated plants.

Male organ - stamen - thin, stalk-like filament with sac at top. Anther - produces haploid spores that develop into pollen grains. Female organ - pistil - contains 3 parts: stigma, style, ovary.

Stigma - sticky top part of flower which extends beyond flower, catches pollen. Style connects stigma to ovary at base of pistil which allows sperm to reach ovules. Ovary - enlarged area at base of pistil - contains one or more ovules. Entire structure - carpal. Ovule contains egg nucleus.

Fruit - mature ovary. As seeds develop from ovules after fertilization - wall of ovary thickens to form fruit. Fruit helps protect seeds while they disperse. Some fruits, dandelion, modified to catch wind. Burrs that stick to animals - fruits.

Fruit develops after pollination triggers hormonal changes - cause ovarian growth. Wall of ovary becomes pericarp (thickened wall of fruit) If flower not pollinated - fruit will not develop. 3 different types of fruits.

Simple fruits come from single ovary (cherries) Aggregate fruit (blackberry) - single flower with several carpals. Multiple fruit (pineapple) develops tightly clustered group of flowers.

Ovules - contain female gametophyte, embryo sac. Angiosperm life cycle starts with mature flower on sporophyte plant and ends with germinating seed.

Anthers of flower produce microspores that form male gametophytes (pollen). Ovules produce megaspores that form female gametophytes (embryo sacs). After its release from anther, pollen carried to sticky stigma of carpal. Plants can self-pollinate; cross- pollination better.

Pollen grain begins growing from stigma toward ovary. Discharges 2 sperm cells into female gametophyte. 1 sperm fuses with egg nucleus to form diploid zygote. Develops into embryo. Embryo has rudimentary root; one (in monocots) or two seed leaves (in dicots), cotyledons.

Other sperm nucleus fuses with 2 polar bodies to form endosperm, (triploid or 3n) in monocots. Dicots - nutrition goes directly to cotyledons. As ovules develop into seeds, ovary develops into fruit. Conditions favorable - germination occurs (seed coat ruptures, embryo emerges as seedling)

Seedling uses food stored in either endosperm (monocot) or cotyledon (dicot) to start growth.

The fruit Ovary of flower develops into fruit, protects enclosed seeds, aids in dispersal by wind or animals. Wall of ovary becomes pericarp, (thickened wall of fruit) Apples - fleshy from swollen receptacles.

As seed develops - enters dormancy - allows it to survive until conditions favorable. 1st organ to emerge from germinating seed - radicle, embryonic root.

Asexual reproduction Plants can clone - vegetative reproduction. Fragmentation - parent plant separates into parts - reform whole plants. Scientists use this process to clone plants used for novelty.

Co-evolution Certain animals only eat certain plants - forced evolution of one another. Plants evolved special fragrances - forces evolution of specific animals to pollinate these plants.

Plants and human welfare All fruit and vegetable crops - angiosperms. Corn, rice, wheat, - grass fruits. Use plants for medicinal purposes; more than 25% of our prescriptions come from plants.