9.1 Xylem
Which process is most responsible for movement of water from roots to leaves of a plant on a hot sunny day?
A. Active translocation of mineral ions in roots
B. Active transport of organic compounds into sieve tubes
C. Raised hydrostatic pressure gradients
D. Evaporation of water from mesophyll cell walls
D. Evaporation of water from mesophyll cell walls
What type of vascular tissue consists of sieve tube members and translocates organic nutrients made in leaves?
Phloem
What allows most plants to continue producing more roots, leaves or stems throughout their life?
A. Auxin
B. Meristems
C. Phloem
D. Cellulose
B. Meristems
1. Pollination is the transfer of pollen grains from anther to stigma. 1. Fertilization is the fusion male and female gametes
1. Leaves of three be a?
2. Leaves of four be a?
1. Monocot
2. Dicot
What is transported in xylem tissue?
A. Sucrose from leaves to fruits
B. Starch from leaves to storage organs
C. Water from roots to leaves
D. Salts from soil to roots
C. Water from roots to leaves
Xylem and phloem are arranged in these in the stem. In dicots they make a ring. In monocots, they are distributed randomly.
Vascular Bundles
How do auxins cause plant shoots to grow towards light?
A. Increase cell division on the side of the stem near the light source
B. Increase cell division on the side of the stem away from the light source
C. Increase cell elongation on the side of the stem near the light source
D. Increase cell elongation on the side of the stem away from the light source
D. Increase cell elongation on the side of the stem away from the light source
This is what pollen travels down to reach the ovum
Define transpiration.
evaporation of water from leaves
A fungicide dissolved in water was applied to the soil in which a rose plant was growing. It later appeared
in the leaves. How did the fungicide reach the leaves?
A. Movement up a water potential gradient
B. Transpiration pull in xylem
C. Translocation in phloem
D. Facilitated diffusion
B. Transpiration pull in xylem
Explain Source and Sink.
Sink: This is the term to describe parts of the plant that use sugar.
Source: This is also known as a supply of sugar.
Identify the relationship between the concentration of auxin and the age of the different leaves.
less auxin as the leaves become older/larger Vice versa
What are the storage structures for nutrients in a seed
cotyledon
Differentiate between the apoplast and symplast routes of sucrose in phloem loading
apoplast – sucrose travels through cell walls then pumped into cytoplasm.
symplast – sucrose travels through cytoplasm of cells via plasmodesmata
Explain the location of the mesophyll (palisade and spongy) and vascular bundle within the leaf.
Palisade Mesophyll: On the upper surface of the leaf, the cells are packed tight and rich in chloroplasts This increases light absorption for photosynthesis
Spongy Mesophyll: On the lower surface of the leaf, the cells are interspersed by space and near stomata This increases gas exchange for photosynthesis
Vascular Bundle: Vascular bundles exist centrally between the two layers (allowing equal access) Have xylem for water transport to leaf & phloem for food transport from leaf
Explain the process of active translocation.
Plants transport organic molecules from source (photosynthetic tissue) to sink (storage organs) These organic molecules are transported via a tube system called the phloem in a viscous fluid called sap Organic molecules are loaded / unloaded via companion cells (either by a symplastic or apoplastic pathway) Active loading of solutes into phloem creates high concentrations that draw water (from xylem) via osmosis The incompressibility of water causes the sap volume/pressure to increase resulting in mass flow Organic molecules are actively unloaded at the sink which causes water to return to the xylem
Compare growth due to apical and lateral meristems.
Apical Meristems:
-Occurs at the tips of roots and shoots
-Responsible for Primary Growth
-Develops into primary Xylem and phloem
-Produces new leaves and flowers
Lateral Meristems
-Occurs at the cambium
-Responsible for secondary growth
-Produces secondary Xylem and phloem
-Produces the bark on trees
Chrysanthemums are an important commercial flower. As a short-day plant, how can growers induce chrysanthemums to flower out of season?
A. Expose plants to short bursts of light for 24 hours
B. Expose plants to 15 hours of continuous light
C. Expose plants to 12 hours of light and 12 hours of darkness
D. Expose plants to 15 hours of continuous darkness
D. Expose plants to 15 hours of continuous darkness
Name the enzyme that catalyzes the hydrolysis of starch into maltose in a germinating seed AND the hormone that intimates the production of that enzyme.
Amylase
Gibberellin
Amylase
Explain how abiotic factors affect the rate of transpiration in terrestrial plants. (at least 5 things)
a. less transpiration/water loss as (atmospheric) humidity rises;
b. air spaces inside leaf are saturated/nearly saturated (with water vapour);
c. smaller concentration gradient with higher atmospheric humidity;
d. more transpiration/water loss as temperature rises/with more heat;
e. faster diffusion / more kinetic energy (of water molecules);
f. faster evaporation (due to more latent heat available);
g. more transpiration/water loss as wind (speed) increases;
h. humid air/water vapour blown away from the leaf;
i. increasing the concentration gradient (of water vapour);
j. more transpiration/water loss in the light;
k. light causes stomata to open / stomata closed in darkness;
Describe how aphid stylets can be used to measure translocation rates
Aphids are insects that feed on sap in phloem via a stylet (which can be severed to collect the sap) If plants are exposed to radioactive CO2, they will produce radioactively labelled sugars Translocation rate can be identified by the time taken for radioisotopes to be detected at various points
Define tropism and give two specific examples
Tropism is the turning of an organism in response to a directional external stimulus.
1. Phototropism: Growth response to light
2. Geotropism: Growth response to gravity
Identify factors that contribute to the germination of a plant.
Germinating seeds require oxygen (for ATP via aerobic respiration), water (to metabolically activate cells), temperature (for optimal enzyme activity) and pH (suitable soil conditions for enzymes) In addition, particular species may require specialised conditions, such as fire, freezing, washing, digestion
Explain how organic compounds are transported within plants. (at least 4 things listed)
a. transported in/translocated in/loaded into phloem
b. in sieve tubes
c. from sources to sinks
d. from leaves/other example of source to roots/other example of sink
e. loading (of sugars/organic compounds) by active transport
f. cause high concentration of solutes (in phloem/sieve tubes)
g. water uptake (in phloem/sieve tubes) by osmosis/water diffuses into phloem
h. rise in (hydrostatic) pressure at source (in phloem)
i. rigid cell walls
j. creates a (hydrostatic) pressure gradient/higher pressure in source than sink
k. active transport from phloem into sink.
l. flow can be in either direction/bidirectional