Chapter 22/23

Plants

Bryophytes

• Life cycle that depends on water to reproduce, lacking vascular tissue, these plants can draw up water by osmosis only a few centimeters

• Include mosses, liverwort, and hornworts• Gametophyte is the dominant recognized stage

of the life cycle and is the state that carries out most of the plant photosynthesis

• Low growing plants• First plants on earth

Seedless Vascular Plants

• Tracheids were an evolutionary innovation that allowed vascular tissue to form: resist pressure

• Xylem and phloem are vascular tissue that can move fluids through the plant body against the force of gravity

• Xylem – carries water upward• Phloem -moves nutrients and carbohydrates

produced by photosynthesis

Cont.

• Allows plants to grow to great heights

• Changed the surface of earth, allowed for the growth of forests

• Mosses, horsetails and ferns

• Have life cycle in which the diploid sporophyte is the dominant stage

Seed plants

• Adaptations that allow seed plants to reproduce without water include flowers (angiosperms) and cones (gymnosperms), the transfer of sperm by pollination and the protection of embryos in seeds

Gymnosperms

• Ancient surviving seed plants

• Gnetophytes: cycads (tropical & subtropical), ginkgoes (rare), conifers (most common), as old as the fossil record

• Conifers; evergreen (do not loose their leaves in winter)

Angiosperms

• Develop unique reproductive organs known as flowers

• Contain ovaries, which surround and protect the seeds, which becomes the fruit

• Excellent way to reproduce – animals eat fruit, travel, excrete seeds, new plant

• Diversity- type and variation of plants: woody, herbaceous,

• Life span: annuals, biennials, perennials

Characteristics

• Monocot• Single cotyledon (1st

leaf)• Parallel veins• Floral parts often in

multiples of 3• Vascular bundles

scattered throughout stem

• Fibrous roots

• Dicot• Two cotyledons• Branched veins• Floral parts often in

multiples of 4 or 5• Vascular bundles

arranged in ring• taproot

Seed Plant Specialized tissue

• Roots; absorb water and dissolve nutrients

• Stems; support for plant body

• Leaves; main photosynthetic system

• Dermal tissue; like “skin”

• Vascular tissue; xylem and phloem

• Ground tissue; lies between dermal and vascular, most photosynthesis happens

Growth

• Meristems; clusters of tissue that are responsible for growth

• Meristematic tissue; undifferentiated cells that can become anything

• Meristematic tissue is the only plant tissue that produces new cells by mitosis

Roots

• Two main types are taproots (mainly dicots) and fibrous roots (mainly monocots)

• Has outside layer, epidermis, a central cylinder of vascular tissue, with large area of ground tissue between

• Anchor plant in the ground and absorb water and dissolve nutrients from soil (N, P, K, Mg, Ca)

Stems

• 3 important functions; 1.) produce leaves, branches and flowers; 2.) hold leaves up to sunlight; 3.) transport substances between roots and leaves

• Monocot: vascular bundles are scattered throughout the stem

• Dicot: vascular bundles are arranged in ring in stem

Cont.

• Primary growth: stems (length) is produced by cell division in the apical meristem, takes place in all seed plants

• Secondary growth: stems (width) lateral meristematic tissue called vascular cambium and cork cambium (eventually becoming tree “rings”

Leaves

• Structure of leaf optimized for absorbing light and carrying out photosynthesis

• Functions: photosynthesis, transpiration, gas exchange

• Stoma – where gas exchange takes place• Guard cells – allows stoma to open and close• Plants keep stomata open just enough to allow

photosynthesis to take place but not enough to allow for excessive loss of water

Transport

• Combination of root pressure, capillary action, and transpiration provides enough force to move water through the xylem of even the tallest plant (pulls up)

• when nutrients are pumped into or removed from the phloem system, the change in concentration causes movement of fluid in that same direction resulting in nutrients being able to move in either direction depending on the needs of the plant