A plant is exposed to for a short period. After 5 minutes, the radioactive carbon is detected in the phloem sieve tubes near the source. After 20 minutes, it's found further down the stem in the phloem. Which observation MOST directly contradicts the mass flow hypothesis?
Sucrose moves bidirectionally in the phloem, sometimes against the concentration gradient.
ATP is required for active loading of sucrose into the sieve tubes.
The concentration of sucrose is higher in the source than in the sink.
Water moves from xylem to phloem at the source and from phloem to xylem at the sink.
Related Questions
Mass flow hypothesis was proposed by?
Munch
Dixon
Nitch
Levitt
The Mass Flow Hypothesis explains the movement of sugars in plants. This movement is primarily from:
Sink to source
Root to leaves only
Leaves to root only
Source to sink
Translocation of sucrose takes place through?
Phloem
Xylem
Cambium
Wood Parenchyma
Researchers manipulate a plant's phloem by selectively blocking plasmodesmata connecting companion cells to sieve tube elements near a leaf. Which outcome would provide the STRONGEST evidence AGAINST the mass flow hypothesis?
Accumulation of sucrose in the leaf and reduced transport to the roots.
Increased turgor pressure in the sieve tubes near the leaf.
Uninterrupted flow of sucrose from the leaf to the roots.
Decreased water potential in the sieve tubes near the leaf.
In the Girdling Experiment, removal of a ring of bark from a woody stem primarily interrupts the flow of:
Sucrose
Water and minerals
Auxins
Gibberellins
Choose the false statement
A prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself.
2 is the only even prime number.
All prime numbers are odd.
1 is a prime number.
During flowering, fruit ripening and development period in plants, which part of the plant act as source?
Whole plant
Stem and leaves and the plant
Photosynthesising leaves and older leaves
Growing parts of the plants
Loading of sucrose in sieve tube elements is
Simple diffusion
Active process
Facilitated diffusion
Osmosis
If the xylem tissue of a plant were selectively removed instead of the phloem in a girdling experiment, what would be the most likely observed effect?
Wilting of leaves
Swelling above the girdle
Accumulation of sugars in the roots
Increased fruit production
When sugars enter sieve tubes, water flows by osmosis, resulting in
Water potential
Osmotic gradient
Turgor pressure
DPD
