Plants Flashcards
Root system-
underground- absorbs
water and minerals from the soil
Shoot system-
aboveground- absorb light and CO2 Stem o Leaves o Flowers/ fruits
Ground tissue system-
plant body–functions in photosynthesis, storage, and support
Vascular tissue system-
conducting system–transports water, minerals, food
Dermal tissue system-
provides covering for plant
Ground tissue system
Composed of 3 different types of tissue. Growing plant cell secretes thin flexible primary cell wall. After stops growing- secondary cell wall- inside primary cell in between plasma membrane and primary cell wall
more rigid and cell can no longer grow after scw
put down. Each of the three tissues contain different types of cell walls, making the structure of the cells range from very soft and flexible (most common parts of plants) to very hard (cells found in wood, bark, nuts, etc)
Xylem
Vascular. conducts water and dissolved nutrient materials from roots to stems and leaves. Cells are hollow and dead at maturity
Phloem
Vascular. conducts food materials (carbs formed by photosynthesis). Cells alive at maturity
Epidermis-
Dermal tissue system. outermost layer of herbaceous plants. Transparent- no chloroplasts. Secrete waxy cuticle which restrict water loss. has stomata.
stomata
pores in epidermis that allow for gas exchange
Guard cells-
surround stomata
Trichomes-
outgrowth or hairs in epidermis (called root hairs in roots)
Periderm-
replaces epidermis in woody plants
Leaf tissues
Upper epidermis covers upper layer, lower epidermis covers lower layer. Mesophyll, bundle sheath, veins
Mesophyll-
photosynthetic ground tissue of the leaf. Loosely arranged with many air spaces- allows for rapid gas diffusion. Palisade mesophyll- closely packed, spongy mesophyll looser.
Bundle sheath-
nonvascular cells surrounding larger veins
Veins-
vascular bundles containing xylem and phloem
Transport in Plant Body
Water and dissolved nutrient minerals are transported from roots to other parts of the plant in xylem- only moves upward. Dissolved sugar is translocated in phloem- can move upward or down. Driven by physical forces, not by a pumping organ
Transpiration-
loss of water vapor by evaporation , mostly through stomata
Environmental factors affecting transpiration:
Higher temps and more light–>stomates to open more
wind and dry air–more transpiration
humidity–less transpiration
Importance: transpiration
responsible for water movement from soil to leaves
cools stem and leaves and Distributes dissolved minerals through plants
how might transpiration be harmful?
Too much transpiration- plant can wilt and die
what cycle is transpiration a part of?
Part of hydrologic cycle- water cycles from ocean and land back to atmosphere, then back to ocean and land Water evaporates from leaves and stems to form clouds in atmosphere
Guttation-
liquid water is forced out of plant. Occurs at night, when no transpiration is occurring but there is moist soil
xylem (water potential)
Remember that water moves from an area of higher water potential to an area of lower (more negative) water potential, meaning an area with more dissolved solutes. When soil is moist, it has a high water potential, although it is slightly negative because it has some dissolved minerals (pure water has water potential of zero). Root cells have a more negative water potential due to many dissolved solutes- therefore water moves by osmosis from soil into root
Tension-cohesion model (or transpiration-cohesion model)
Loss of water through transpiration in leaves causes a tension that extends from leaves down to stems and roots, drawing water up the stem xylem to the leaf cells. Possible only as long as there is an unbroken column of water in xylem throughout the plant- maintained by cohesion of water molecules to each other and adhesion of water molecules to xylem. Because there is a water potential gradient from the least negative (soil) up through the plant to the most negative (atmosphere), water is pulled up from soil through plant. Tension-cohesion model is powerful enough to pull water upward 500 ft.
phloem system
Before loaded into phloem, glucose produced during photosynthesis is converted into sucrose. Fluid can move both upward and downward. Sucrose moves from a source to sink
Controlling water loss at the stomata
Controlled by changes in shape of guard cells
guard cells opening up
Water moves into guard cells- they become turgid and bend slightly, moving apart to produce a pore
guard cells closing
Water leaves guard cells- they become flaccid and the cell walls collapse, closing the pore
How does blue light open stomata?
Pigment in guard cells is stimulated by blue light. Triggers activation of enzymes called kinases located in the cell membrane. These enzymes cause potassium ions to flow in, followed by water bc of water potential, and the stomata open