Plant Life Cycles Ch 6 section 1 and 2 What Are the Functions of Roots, Stems, and Leaves? Roots -3 Main functions -anchor the plant in the ground -absorbs water and minerals from the soils -sometimes stores food Types of Roots - Fibrous - consists of many similarly sized roots that form a dense tangled mass. - remove lots of soil when pulled out of the ground - examples- grass, corn, onions -Tap - one long, thick main root - smaller, roots branch off the main root - hard to pull out of the ground - examples- carrots, dandelions, cactus Root Structure Root cap- rounded and covers the tip of the root Root hairs- grow out of the roots surface Absorb water and minerals Help anchor plant in soil Tissues Xylem- water and nutrients move through this Phloem- transfers food Root Structure. Plant Structures Stems Two Main functions - carries substances between the plants roots and leaves - provides support for the plant and holds up the leaves Structure of the Stem -can be either woody (hard and rigid) or herbaceous (contain no wood and are often soft). Both contain phloem and xylem tissues Woody Stems Outer layer is bark (protective) Cambium creates new phloem and xylem Annual rings Represents a trees yearly growth Made of xylem Xylem that forms in the spring are large and have thin walls because of rapid growth. Produce a wide, light brown ring Xylem that forms in the summer grows slowly, are small and have thick walls. Produce a thin, DARK ring One pair of light and dark rings represents a years growth In wet years the trees annual rings are wide. In dry years, the rings are narrow Leaves Capture the suns energy and carry out the food making process of photosynthesis. Structure of a Leaf Surface layer Stomata- small openings that control the gasses entering and exiting the leaf. Inside the leaf Veins containing xylem and phloem The Leaf and Photosynthesis Cells containing the most chloroplasts are found near the upper surface Carbon dioxide enters through the stomata Water travels from the roots through the xylem tissue Controlling Water Loss Transpiration- water evaporating from plants leaves Prevented by closing the stomata Leaf Structure Each structure helps a leaf produce food. Plant Structures Stomata Stomata can slow water loss. Plant Structures How Do Seeds Become New Plants Seed Structure 3 main parts Embryo Young plant that develops from a fertilized egg Has the roots, stems, and leaves of new plant Cotyledons (seed coats) Food is either stored here or outside the embryo Seed coat Outer covering that protects the seed and food from drying out Allows the seed to remain inactive for long periods of time In many plants the seeds are surrounded by a fruit Seed Dispersal Scattering of seeds Methods Animals eat the fruit, the seeds pass through digestive system and are deposited in new areas Attach to articles of clothing or fur with hook like structures and fall off in a new area Water and wind dispersal Seeds that are dispersed far away from parent plant has a better chance for survival because theres no competition Germination Occurs when the embryo begins to grow again and pushes out of the seed Begins when the seeds absorbs water. Roots grow downward first and then stem and leaves grow upward. What Are the Structures of a Flower? Main Function of a flower is reproduction -A typical flower contains Sepals Petals Stamens Pistils The color, shape and scent of a flower attracts insects and other animals that ensure that pollination occurs. Pollination is transfer of pollen from male structures to female structures Sepals and petals Sepals enclose the bud and protect the developing flower- often green in color Petals are found under the sepals and are generally the most colorful part of the flower Stamens Male reproductive part Filament- thin stalk Anther- contains the pollen- found at the top of the filament -Pistils Female reproductive part Stigma- sticky tip- catches the pollen Style- tube connecting the stigma to the ovary- pollen travels down it Ovary- hollow base that contains the eggs, protects the seeds as they develop Ch 6 Lesson 2 What are the Stages of a Plants Life Cycle? Two Different Stages Sporophyte First stage where plant produces spores or seeds (tiny cells) that can grow into new organisms Gametophyte Second stage that produces the sex cells; sperm or egg. Plant Reproduction Plant Life Cycle All plants go through two stages in their life cycle. Which are the sporophyte and gametophyte stages? Angiosperms are classified based on the length of their life cycle Annuals Flowering plants that complete their life cycle within one growing season Examples- marigolds, petunias, wheat, cucumbers Biennials Complete their life cycle in 2 years. First year- germinate and grow roots, very short stems and leaves Second year- grow larger and produce flowers and seeds Examples- parsley, celery, and foxglove flowers Perennials Flowering plants that live for more than 2 years Flower every year How Do Plants reproduce? All plants undergo sexual reproduction that involves fertilization. Fertilization occurs when the sperm enters the egg. The fertilized egg is called a zygote Asexual Reproduction Doesnt involve flowers, pollination, or seeds Can happen quickly Can reproduce unfavorable traits since theres no new genetic information being passed to offspring Non Vascular and Seedless Plants Release spores, instead of seeds, that grow into gametophytes. When the gametophytes produce the egg and sperm there must be water available for the sperm to swim to the egg. Examples- mosses, liverworts, hornworts, ferns, and horsetails. Gymnosperms Have reproductive structures called cones Reproduction Steps Cone Production Covered in scales Two types- male and female Pollen Production and Ovule Development Male cones produce pollen Female cones produce ovules that contain an egg. Female cones contain at least one ovule at the base of each scale. The ovule later turns into a seed Pollination Transfer of pollen to egg is done by wind. Fertilization Ovule closes and seals in the pollen. Scales close and zygote develops Seed Development Female cones remain on the tree while seeds mature Cone grows in size, sometimes taking up to 2 years to mature When mature, the scales open and release the seed into the air Angiosperms Pollination Flower is pollinated when pollen lands on the stigma Pollen travels down the style to the ovary. Zygote develops within the seeds embryo Fruit Development and Seed Dispersal As the seeds develops the ovary changes into fruit, which encloses the seeds.