Plants 2 Read 422-464 Study for Test next class NR 4 due in a week(ish)
Review: • Gymnosperms: • Mainly conifer trees, naked seeds, thick bark • Eudicots (Angiosperms): • Flowering plants, branched veins, 4/5 petals • Monocots (Angiosperms): • Flowering plants, parallel veins, 3 petals
Defense • 4 major strategies for defense: • Chemical • Growth of non-essential structures • Encourage predation from other species • Mechanical
Chemical and Mechanical • Production of non-essential organic compounds that do not aid in growth or reproduction of the plant. • toxins • Production of structures on leaves and stems discourage herbivores through injury or death. • Thorns, waxy coatings, poison spines, sap
Mutualism • Some plants develop structures to house another species that will protect it from predators.
Flower structure • A flower is a reproductive organ in angiosperm plants. • Considered a modified stem • Arranged in whorls (spiral patterns) • Whorls from outer to inner: • Sepals, petals, stamen, pistil
Perfect flowers? • A flower is considered “perfect” if it has both a stamen and pistil. • These flowers are also known as bisexual or hermaphroditic. • If a flower is “imperfect” it may only contain male or female parts. • If both male and female parts are on the same plant (but different flowers)monoecious • Male and female flower parts are on different plants dioecious.
Flowers are for reproduction • The main purpose for flowers is to mediate the joining of pollen to ovary (sperm to ovule). • Pollination by insects and flower phenotype are adaptations to increase the likelihood of fertilization. • Many times, this coevolution can be seen having negative effects when one species or the other becomes endangered.
Fruit • A fruit is a ripened ovary and surrounding tissues. • A main way that plants spread seeds. • In cooking, many culinary vegetables are actually fruits: • Squash, pumpkin, cucumber, tomatoes, peas, beans, corn, eggplant, chilies, etc • Nuts are also types of fruit, but are often classified as edible seeds (peanuts, pistachios)
Types of fruit • 3 types of fruit: • Simple, aggregate, multiple • Simple: Comes from one pistil. (ex: avocado) • Aggregate: Comes from a flower with many pistils (ex: raspberry) • Multiple: multiple flowers that create one massive fruit (ex: pineapple) • Seedless fruit: • Caused by either breeding or because fruit is not a result of fertilization (plant reproduces via asexual means).
Fruit Anatomy • Exocarp- tough skin with oil glands and pigments • Mesocarp- The fleshy portion of the fruiting body. • Endocarp- The portion of the fruit that directly surrounds the seed. • Seed- The immature plant that will begin to grow under the right conditions.
Plant hormones • 5 major hormones: • Abscisic acid: (ABA) prevents leaf & stem growth. • Auxin: influence cell growth, bud formation, root initiation • Cytokinin: influence shoot formation • Ethylene: fruit ripening • Gibberellin: seedling growth, flowering, reverses ABA