Plants Plant Characteristics and Special Functions

Overview of Plants  all shapes and sizes  all types of environments

Common Characteristics of Plants  About 260,000 species of plants live on Earth today.  All plants: 1.Are multicellular 2.Have a nucleus surrounded by a cell wall. 3.Are producers – capture light from the Sun. 4.Have life cycles divided into two stages (generations).

Special Functions  Below ground: roots  Absorb water and nutrients from soil.  Transport materials to leaves through the stem.  Above ground: stems and leaves = shoot system  Leaves use materials + CO2 to make sugars and carbohydrates through photosynthesis.

Transporting Materials  Materials move through a vascular system.  Stems transport the materials from one part of the plant to another.  The vascular tissues are bundled together from the root to the leaves; look like tubes.

Transporting Materials - Tissue  Xylem: carries water and dissolved nutrients up from roots.  Phloem: transports energy-rich materials, such as sugar, down from leaves.  Both are long, hollow tubes that contain fibers to support the body of the plant.  Xylem is a little larger.

Transporting Materials - Tissue

Making Sugars - Photosynthesis  Plants make sure through photosynthesis.  What is the formula?  Co2 + H2O + sunlight  oxygen + glucose (C6H12O6)  Where does it take place?  In the chloroplasts, which contain chlorophyll

Inside of the Leaf  Upper layer is filled with chloroplasts.  Vascular tissue is located toward the center.  Stomata, or tiny openings, are located on the bottom of the leaf – gas exchange occurs here (CO2 comes in, O2 goes out).

Controlling Gas Exchange  Stomata can open and close to let CO2 and oxygen in and out.  Water is able to evaporate from open stomata  transpiration.  Sunlight and wind cause transpiration.

Water Loss  Plants have a waxy cuticle, or protective layer, to prevent too much water from evaporating.  Stomata can open and close to prevent this, also.

Adapting to Environment - Cactus  Special adaptation – no leaves – uses spines instead.  Photosynthesis occurs in the stem, where the cactus is able to hold more nutrients without the threat of transpiration.

Plant Growth  Plants grow as long as they live.  They get bigger when cells at the tips of their roots and stems divide and multiply more quickly than other cells.  Only stems grow leaves – leaves grow from buds.

The Stem – Three Functions  Holds the vascular system  Provide support and plant structure  Store sugars produced by photosynthesis

Soft Stems  Wildflowers, garden flowers, and vegetables  Survive by using the carbs stored in its roots to grow new, soft, green stems and leaves in warmer weather.

Woody Stems  Trees and shrubs  Tough, thick stems that do not die each year.  Keep growing longer/thicker  Tough xylem layer  wood

Plants Mosses and Ferns

 Begin to appear about 475 million years ago.  Probably looked like green algae found in shallow ponds today. Plant Life

 Had to adapt from aquatic to land organisms.  They had to be able to get all of their nutrients, water, and sunlight in a new environment.  Ancestors of mosses and ferns – evolved from algae. The First Plants

 Mosses are simpler  Liverworts and hornworts are closely related  Ferns appeared later Mosses and Ferns

 Had to adapt from aquatic to land organisms.  Ancestors of mosses and ferns – evolved from algae. The First Plants

 Moss cells have a cell wall and storage areas (central vacuoles).  Do not grow large, but they have structures that act like roots, stems, and leaves.  Nonvascular: no vascular tissues (xylem and phloem); the nutrients just move from cell to cell. Mosses are nonvascular.

 first part – moss grows and maintains itself.  Second part – spore producing stage; there must be enough water.  Spore: single reproductive cell that has a hard covering; small and transported through the air.  Plants that grow from spores – first generation. Moss Reproductive Cycle

 When you see a clump of moss, it contains both male and female reproductive structures that produce reproductive cells.  Male cells need water in order to move to and fuse with a female cell. Moss Reproductive Cycle

 Fertilized eggs grow into a small stalk wit a capsule on the end – the second generation.  Meiosis produces thousands of spores inside the capsule.  When they are released, the cycle starts over. Moss Reproductive Cycle

 Ferns, horsetails, and club mosses were the first vascular plants on Earth.  Can grow much larger because they have support.  Roots can branch out more underground, stems go grow taller and branch out to smaller stems, and leaves can grow – more sugars (more photosynthesis). Ferns are vascular plants.

 Leaves (fronds) contain clusters of spores on the back.  Spores grow into tiny structures that are close to the ground; these contain the male and female cells.  First generation Fern Reproduction

 When there is enough water, male cells move to fuse with female cells.  The fertilized egg forms a plant with new fronds – the second generation.  As plant grows, female structures die away and clusters of spores reproduce. Fern Reproduction

 A small piece can separate and grow into a new plant.  Allows plants to spread more easily.  But, provides less diversity. Moss/Fern– Asexual Reproduction

Plants Seeds and Pollen

 Seed: young plant enclosed in a protective coat.  The seed contains all of its nutrients inside of the coat – allowing it to survive harsh conditions. Seeds

 Fertilization brings about the next generation of plant, beginning with the embryo: the immature form of an organism that has potential to grow. Seeds

 The seed will begin to grow when conditions are just right.  Germination: beginning of growth of a new plant from a spore/seed.  Takes in water and uses nutrients inside seed to grow. Seeds

Both Spores - Multicellular embryo- Protective coat to allow survival in harsh conditions - Made of single cell - Contains nutrients- Contains parent’s DNA - No nutrients Seeds vs. Spores.

 Seed plants are more commonly found for a few reasons.  Carried by wind, water, and animals.  Water not needed for male cells to fertilize female cells. Seeds

 Pollen: small multicellular structure that holds a sperm cell.  When a pollen grain attaches to the part of a plant that contains an egg, pollination occurs. Pine Trees

 1. meiosis occurs in the pine cones, producing male and female cells; each tree has M and F cones.  2. Male cones: pollen; female cones: egg cells are found in cone scales. Pine Trees – Life cycle

 3. female cone produces sticky substance and the pollen lands on it. Pollen tubes grow to allow male cells to fuse with female cells.  4. fertilized egg becomes an embryo in a seed which is released from the pinecone. Pine Trees – Life cycle

 Meiosis and fertilizaiton  Pollen grain + egg cell = first generation  Seed + trees that grow = second generation Pine Trees – Life cycle

 Gymnosperm: seeded plants  Have been on Earth for 250+ million years.  They produce seeds that are not in fruit.  4 types Gymnosperms

 Cone-bearing trees  Pine, fir, spruce, redwood, etc.  Cold climates  needle-shaped leaves Conifers

 Cycads: palm-like plants; tropical  Gnetophytes: tropical  Ginkgoes Others

Plants Angiosperms

 Angiosperm: flowering plants  Flowers and fruit  Most plants on Earth today are angiosperms. Angiosperms

 Male cells found in pollen.  Female cells develop into embryos in a seed.  Separate structures for male and female structures.  The M and F cells are contained in a flower. Angiosperm Life Cycle

 Flower: reproductive structure  Egg cells develop in ovary.  Once eggs are fertilized, the ovary grows into a fruit. Angiosperm Life Cycle

 1. flower is reproductive structure; anthers are male parts and pistils are female parts. Meiosis occurs in both parts.  2. pollen is released and caught on the pistil; pollen tube grows and an egg cell matures. Cherry Tree Life Cycle

 3. fertilization occurs and an embryo forms with a seed coat; ovary  fruit.  4. fruit may fall or be eaten; if seed lands in a suitable spot, germination occurs. Cherry Tree Life Cycle

 new shoots can grow out of a parent plant and grow a new plant.  Strawberries do this.  Helps when environmental conditions are not suitable. Angiosperms Asexually Reproduce

 Sepals: leafy structures that enclose flower before blooming; form base for flower.  Petals: leafy structures arranged in a circle around the pistil; colorful to attract plant pollination. Flowers

 Stamen: male rep. part; filament-stalk and anthers- produces sperm cells.  Pistil: female rep. part; ovary-at base, contains egg; stigma- where pollen attaches. Flowers

 Fruit = ripened plant ovary.  Some have many seeds (apple), others that just one (cherry).  Some are fleshy (corn), others are dry (peanuts). Fruit

 Plants are food for animals; animals move pollen from flower to flower and seeds place to place.  Animals that move pollen are pollinators.  Advantage of animal pollination: pollen goes to wear it is needed most. Animals and Angiosperms