Plants

Plant Evolution and Classification Preventing Water Loss Reproducing by Spores and Seeds Transporting materials throughout the plant.

Classifying Plants 2 groups based on the presence of vascular tissue Nonvascular Plants Vascular Plants Seedless-fern like Seeded- Maples, and Pine

Classification Nonvascular Plants Phylum Bryophyta Phyla Haptophyta and Anthocerophyta

Seedless Vascular Plants Phylum Psilotophyta Phylum Lycophyta Phylum Sphenophyta Phylum Pterophyta

Vascular Seed Plants Gymnosperms Angiosperms Phylum Cycadophyta Phylum Ginkgophyta Phylum Gnetophyta Phylum Coniferophyta Angiosperms Phylum Anthophyta

Classes of Angiosperms Monocot On cotyledon Parallele Venation Scattered Flower parts in 3’s Fibrous Dicot 2 cotyledons Net venation Radially arranged vascular bundles Flower parts in 4 and 5 Taproot

Plant Structure and Function Plant Cells 3 types Parenchyma Collenchyma Sclerenchyma

Parenchyma Loosely packed cube-shaped or elongated cells that contain large central vacuole. Metabolic functions, photosynthesis and storage of water and nutrients. Example~ Fleshy part of an apple

Collenchyma Cells Thicker cell walls, irregular shape Usually grouped in strands and are specialized for supporting regions that are still growing. Celery

Sclerenchyma Cells Thick rigid cell walls. Support and strengthen the plant in areas where growth is no longer occurring. Gritty texture of a pear fruit.

Tissue Systems Dermal Tissue Ground Tissue Vascular Tissue

Dermal Tissue Forms the outer coverings in plants Consists of the epidermis, the outer layer made of parenchyma cells. Roots~ absorption, protection Stems~ gas exchange, protection Leaves, gas exchange, protections.

Ground Tissue All 3 cell types Storage, metabolism and support.

Vascular Tissue Functions in transport and support Xylem-dead Phloem-living 2 major components for xylem Tracheid Vessel Element

Tracheid Long thick walled sclerenchyma cell with tapering ends. Water moves from on tracheid to another through piths

Vessel Element A sclerenchyma cell that has either large holes in the top and bottom or no end wall at all. Stacked to form long tubes called vessels.

Sieve Tube Member Conducting parenchyma cells of angiosperm phloem. Compounds move from one to another through sieve plats. Each cell has a companion cells, specialized parenchyma cell.

Growth in Meristems (Primary Growth) Meristem- regions where cells continuously divide for plant growth. Apical Meristem- located in the tips of stems and roots. Intercalary meristems- growth between the nodes of plants.

Root Structures

Root Structures Root Cap Root Hairs Covering of cells that protects the apical meristem. Produces a slimy lubricant. Root Hairs Extensions of the epidermal cells. Increase the surface area.

Primary Growth in Roots Roots increase in length cell division elongation maturation in the root tip Dermal tissue matures to form the epidermis Ground tissue matures into 2 regions Cortex and Endodermis

Cortex Located just inside the endodermis. Largest region of the primary root. Parenchyma cells

Endodermis Inner cylinder of the cortex. Vascular tissue in roots matures to form the innermost cylinder Dicots and gymnosperms~ xylem makes of the central core of the root.

Monocot Root Cross Section

Dicot Stem

Stems

Primary Growth in Stems Apical meristems give rise to the dermal, ground and vascular tissue. Dermal- epidermis Ground- cortex and pith Cortex- just inside the epidermis Pith- located in the center of the stem. Vascular- xylem and phloem

Monocot Stem

Vascular Bundle of Monocot

Dicot Stem

Secondary Growth Conifers and Woody dicots Increases in girth or lateral dimension Occurs at lateral meristems Vascular cambium Gives rise to secondary xylem and phloem Cork cambium Gives rise to bark

Vascular Cambium Cells on the outside differentiate into phloem Cells on the inside differentiate into xylem Only new xylem transports water. Older xylem located at the center is only for support.

Annual Rings

Leaves

Monocot Leaf Upper Epidermis Mesophyll Lower Epidermis Xylem Phloem

Dicot Leaf Upper Epidermis Xylem Palisade Mesophyll Spongy Mesophyll Phloem Lower Epidermis Guard Cells with Somata

Leaf Structures Epidermis Palisade Mesophyll Spongy Mesophyll Guard Cells Vascular Bundles

Epidermis A protective covering of one or more layers of cells. Covered by the cuticle Cutin Transpiration

Palisade Mesophyll Parenchyma cells Numerous chloroplasts

Spongy Mesophyll Parenchyma cells Loosely arranged Air spaces allow for gas exchange

Guard Cells Specialized epidermal cells that control the opening and closing of stomata. Controls gas exchanges with the environment.

Vascular Bundles Consists of xylem and phloem tissues Contains bundle sheath cells that prevent gas from entering the vascular bundle.

Transport of Water Water and dissolved minerals enter the roots through root hairs by osmosis. 2 Possible Pathways Apoplast Symplast

Apoplast Water moves through cell walls from one cell to another without every entering the cells.

Symplast Water moves from one cell to another through the symplast. Water moves from the cytoplasm of one cell to the cytoplasm of the next through plasmodesmata. Small tubes that connect the cytoplasm of adjacent cells.

When water reaches the endodermis… Water can continue into the vascular cylinder only through the symplast pathway. Water that is moving via the apoplast pathway is blocked by the suberin that permeates the casparian strip. Water can enter through the endodermal cells along with K+, but Na+ is blocked. Water then reaches the vasuclar cylinder where xylem tissue (tracheids and vessels) conduct the water up the plant.

Water Movement Up the Plant 3 Mechanisms Osmosis Capillary Action Cohesion-tension theory

Cohesion-tension Theory 3 Major Concepts Transpiration Cohesion Bulk Flow

Transpiration The evaporation of water from plants. Water evaporates through the leaves creating negative pressure to develop in the column.

Cohesion The molecular attraction between like substances. The water molecules “stick” together creating a single column of water molecules.

Bulk Flow When a water molecule is lost from a leaf by transpiration it pulls up behind it an entire column of water molecules.

Transport of Sugars 4 Step process Sugars enter the sieve-tube members via active transport. Water enters the sieve-tube members. Pressure in sieve-tube members at the source moves water and sugars to sieve-tube members at the sink through sieve tubes. As a result pressure builds causing the water and sugars to move. Pressure is reduced in sieve-tube members at

Plant Movements Tropisms Nastic Movements A plant movement that is determined by the direction of an environmental stimulus. Positive Negative Nastic Movements Plant movements that occur in response to environmental stimuli but are independent of the direction of the stimuli.

Tropisms Phototropism Thigmostropism Gravitropism

Phototropism Stimulus Hormone Function Light Auxin Light causes the production of auxin to move to the shaded side. As a result the cells on the shaded side are elongated faster then the lighted side. The plant bends towards the light.

Thigmotropism Stimulus Function Contact with an object Allows for vines to “climb” walls. Tendrils will coil around objects.

Gravitropism Stimulus Hormone Function Gravity Auxins, Gibberellins Allows for roots to grow down. Allows for shoots (stems) to grow up at the apical meristem.

Photoperiodism Is the response of plants to changes in the photoperiod, or the relative length of daylight and night. Plants maintain a circadian rhythm External clues such as dawn and dusk reset the clock.

Phytochrome The protein involved used in maintaining the circadian rhythm. 2 Forms depending on the wavelength of light that the phytochrome absorbs. Pr: Phytochrome red (wavelength of 660nm) Accumulates at night Pfr: Phytochrome far-red (730nm) Resets the circadian-rhythm clock Reversible relationship between Pr and Pfr When Pr is exposed to red light it is converted to Pfr When Pfr is exposed to far-red light it is converted to Pr

Critical Night Length CNL is responsible for resetting the circadian-rhythm clock. Brief dark periods during the day have no effect on the clock. Flashes of red light at night cause the clock to be reset.

Flowering in Plants Regulated by the photoperiod. 3 types of plants Long-day Plants flower in the spring and early summer when day light is increasing. Short-day Plants flower in late summer and early fall when daylight is decreasing. Flower when daylight is less than a critical length. Day-neutral Do not flower in response to daylight changes.