Mastering Bio- Chpt 29

How do prokaryotes contribute to plant health?

-Prokaryotes secrete chemicals that stimulate plant growth and protect plant roots from disease. -Prokaryotes fix atmospheric nitrogen.

What characterizes the rates of photosynthesis and transport in a plant on a dry cloudy day?

Both the photosynthesis and transpiration rates are low. (On a cloudy day with low soil moisture, the photosynthesis rate is low and stomata are closed, so the transpiration rate is low.)

Which tissue acts as a filter on the water absorbed by root hairs?

Endodermis (Endodermal cells filter solutes from water and allow them to pass through to the vascular tissue.)

True or false? Plants use both active and passive transport processes to transport ions against their concentration gradients.

False (Plants use passive transport, which requires no energy expenditure, to transport ions down their concentration gradients, but they can only use active transport, which requires energy in the form of ATP, to transport ions against their concentration gradients.)

True or false? Soil texture affects the amount of water available to plants; water is held best by clay and sand particles.

False (Soil texture does indeed affect the amount of water available to plants, but water is held best by the smallest soil particles, clay and silt.)

True or false? Root pressure can move water a long distance up the xylem because of the higher water potential of the xylem in comparison to the water potential in the surrounding cells.

False. (Root pressure can move water a short distance up the xylem because of the lower water potential of the xylem in comparison to the water potential in the surrounding cells.)

True or false? The rate of sugar transport in a plant depends on the rate of photosynthesis, the rate of transpiration, and the difference in turgor pressure between the source and the sink.

False. (While the rate of photosynthesis and the difference in turgor pressure between the source and the sink do influence the rate of sugar transport in the phloem, the rate of transpiration does not; transpiration mainly influences the rate of water transport through the xylem.)

If a wide-spectrum fungicide that kills all fungal species were used extensively in a forest, what effects would you expect the treatment to have on the forest vegetation?

It would greatly reduce the ability of most plants to take up water and minerals from soil. (Most plants rely on mycorrhizal fungi to take up water and minerals from soil. If these fungi were killed, it would greatly reduce the ability of most plants to take up water and minerals from soil. Read about fungi and plant nutrition.)

How do plants obtain organic molecules?

Plants synthesize their own organic molecules. (As autotrophs, plants synthesize their own organic molecules. They incorporate inorganic nutrients taken up from soil into components of these organic molecules. Read about plants' uptake of nutrients.)

What term describes an area where sugars are used or stored?

Sink (A sink is an area where sugars are used or stored; typically, these are the roots and fruits of a plant.)

Why is the decomposition of dead organisms important for soil formation?

The process adds organic matter to the soil, which is necessary to support the growth of larger plants. (Decomposition of dead organisms adds organic matter, or humus, to the soil; humus is necessary to support plant growth.)

Which of the following statements about xylem transport is true?

Water and minerals move through the root cortex into the xylem and upward through the stem and into leaves. (Water and minerals that are taken up in the soil are transported from roots to leaves by the xylem.)

Which of the following is a correct statement about a difference between xylem and phloem transport?

Xylem sap moves up; phloem sap moves up or down. (The direction of movement in xylem is from roots to leaves. Phloem sap is transported throughout the plant from source to sink.)

Which of these ions is most likely to be leached from the soil?

chlorine ions (Chlorine ions are negatively charged and are therefore not likely to be bound to negatively charged soil particles.)

Which of the following is a symptom of magnesium deficiency in plants?

chlorosis (Magnesium is a component of chlorophyll. Chlorosis is the yellowing of leaves due to a magnesium deficiency.)

Humus consists of _____.

decomposing organic material (Humus is the decaying organic material found in soils. It provides energy for many soil organisms and is rich in nitrogen.)

Acid precipitation _____.

decreases soil fertility (Acid precipitation promotes cation exchange. However, the precipitation then washes the ions away before they can diffuse into root hairs.)

How do cations enter root hairs?

diffusion (Cations diffuse into root hairs.)

The binding of H+ ions to soil particles _____.

displaces mineral cations (Positively charged hydrogen ions displace positively charged mineral ions on soil particles.)

The release of CO2 into the soil results in the formation of _____.

hydrogen ions and carbonate ions (When carbon dioxide combines with water hydrogen in the soil, cations and carbonate anions are released.)

Topsoil _____.

is a mixture of rock fragments, living organisms, and humus (Topsoil is produced by the erosion of rock by living organisms and is rich in decomposing organic matter (humus).)

For an element to be considered a macronutrient _____.

it must be required in relatively large amounts

The sundew plant has to digest insects because _____.

it obtains nitrogen from their bodies that it cannot get from the soil (The sundew lives in nitrogen-poor soil and obtains its nitrogen from the digestion of insects.)

Plants must always compromise between _____ and _____.

maximizing photosynthesis ... minimizing water loss (Structures, such as broad leaves, that enhance photosynthesis also maximize water loss. Plant form is generally a compromise between the two, depending on the plant's environment.)

What is an adaptation that enhances the uptake of water and minerals by roots?

mycorrhizae

The mechanism that explains the movement of sugars throughout a plant is called the __________________________.

pressure-flow hypothesis

What process is the source of the CO2 that root hairs release into the soil?

respiration (CO2 is a by-product of respiration.)

The solute most abundant in phloem sap is _____.

sugar (Phloem transports sugar from a sugar source to a sugar sink.)

Water that moves through a plasmodesma is flowing in the _____________________.

symplastic pathway

The proton pump _____.

uses the energy stored in ATP to produce a hydrogen ion gradient across membranes. (This proton gradient occurs across a membrane.)