Plants Day 3

Plant Reproduction Plants complete their life cycle by alternating between two phases. Diploid Phase: plant produces spores. Haploid Phase: plant produces gametes. 2

Plant Reproduction Life cycle phases look different among various plant groups. Life Cycle of Nonvascular Plants: Moss Nonvascular plants have a dominant gametophyte (haploid) phase is dominant and require water to reproduce. 3

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Plant Reproduction Life Cycle of Seedless Vascular Plants: Ferns The sporophyte (diploid) phase is dominant phase. Sori are clusters of sporangia (spore-producing sacs) that are found on the underside of the fern leaf. A mature sporophyte is called a fiddle head. 5

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Plant Reproduction Life Cycle of Seed Plants: Conifers The sporophyte (diploid phase) is the dominant phase. Produce two types of spores that develop into male and female gametophytes (pollen is produced in male cones, while eggs are produced in female cones). Pollination occurs in a cone-bearing plant when a pollen grain reaches the small opening of an ovule in the female cone. After pollination, eggs are produced inside the ovule and a pollen tube begins 7

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Plant Reproduction Life Cycle of Seed Plants: Flowering Plants Flowers contain reproductive organs protected by specialized leaves. The outermost layer of a flower is made up of sepals. Sepals are modified leaves that protect the developing flower, collectively called the calyx. 9

Plant Reproduction Petals are the modified leaves inside of sepals. Their bright colors often help to attract animal pollinators. (Petals collectively are also called the corolla.) 10

Plant Reproduction Flowers can be a single sex or contain both. A stamen is the male structure of a flower. The stamen includes: filament (holds up anther) anther (produce pollen) anther stamen filament 11

Plant Reproduction The female structure is called a carpel. Flowers can have several carpels fused together called a pistil. Structure of pistil: stigma (sticky; where pollen lands) style (tube that leads to ovary) ovary (female reproductive structure) stigma style pistil ovary 12

Fruits: Can be derived from an ovary and sometimes other flower parts As a fruit develops, the ovary wall thickens to form the pericarp (divided into up to 3 layers: exocarp, mesocarp, endocarp) Simple fruits: derived from a single ovary or compound ovary of several fused carpels. ex. Legumes: peas, beans Fleshy fruits: thick fleshly mesocarp. ex. peaches, cherries, tomatoes Accessory fruits: bulk of fruit is from receptacle instead of ovary. ex. Apples Compound fruits: develop from several ovaries. ex. Blackberries, raspberries Aggregate fruit: many separate carpels. Ex. Strawberries Multiple fruit: different carpels that belong to several flowers that as the ovaries mature, they fuse together. ex. pineapples

Plant Reproduction Flowers allow for more efficient pollination than occurs in most gymnosperms, which rely on wind for pollination. Insects and other animals feed on pollen or nectar and transfer pollen when feeding. 14

Plant Reproduction Fertilization takes place within the flower. Pollination One cell in the pollen grain grows into a pollen tube that extends toward the ovule. The other cell in the pollen grain divides by mitosis, producing two sperm that travel down the pollen tube. One fertilizes the egg. The other sperm combines with the polar nuclei to become a cell with a triploid (3n) nucleus that will become the endosperm, a food supply for the developing plant embryo. The process is called double fertilization which only happens in flowering plants. 15

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Plant Reproduction Fruits and Seed Dispersal The function of fruit in flowering plants is to help disperse seeds to eliminate competition with parents. Animals, wind, and water can spread seeds. Examples: Bird eats a blackberry and defecates out the seed away from the bush. Dog gets burr in fur and scratches it off in a new location. Dandelion fluff is actually a fruit with a seed attached and is spread by the wind. Coconuts float thousands of miles across oceans and arrive on different islands. 17

Plant Reproduction Seeds will not grow until conditions are favorable. This period before growth is called dormancy. Examples: Strawberry seeds remain dormant until their seed coats are weakened in the digestive tract of an animal. Other seeds have waterproof seed coats that can only be cracked by winter ice. 18

Plant Reproduction When a seed begins to grow it is called germination. Embryo takes up water and breaks out of seed coat. Seedling growth begins. Enzymes are activated inside the seed to help digest the endosperm. 19

Plant Reproduction Plants can reproduce asexually with from a fragment of a stem, leaf, or root. Example: prickly pear cactus 20

Plant Reproduction Vegetative reproduction is a type of asexual reproduction in which stems, leaves, or roots attached to the parent plant produce new individuals. Example: aspen trees 21