#Question id: 10917
#Unit 6. System Physiology – Plant
Photosynthetic sugar molecules are transported via phloem to other parts of the plants. The following aspects are associated with sucrose unloading in phloem and its transport;
a) The presence of plasmodesmata is assumed to provide apoplastic transport. An absence of plasmodesmata between cells indicates an nonfunctional symplastic continuity
b) Phloem unloading and short-distance transport can occur via symplastic as well as apoplastic pathways
c) Both unloading and the short-distance pathway appear to be completely symplastic in some young eudicot leaves, such as sugar beet and tobacco
d) An apoplastic step is required in developing seeds because there are no symplastic connections between the maternal tissues and the tissues of the embryo
Which of the following combination is INCORRECT?
#Question id: 10918
#Unit 6. System Physiology – Plant
The import into sinks such as developing roots, tubers, and reproductive structures, In many ways the events in sink tissues are simply the reverse of the events in sources. The following steps are involved in the import of sugars into sink cells such as;
#Question id: 10919
#Unit 6. System Physiology – Plant
Both of these observations—________X__________and________Y__________—support the existence of mass flow in the sieve elements of the phloem.
#Question id: 10920
#Unit 6. System Physiology – Plant
The pressure-flow model, first proposed by Ernst Münch, Phloem loading at the source and phloem unloading at the sink establish the pressure gradient.
a.) In source tissues, an accumulation of sugars in the sieve elements generates a lower or negative solute potential (ψs).
b.) source tissue, causes a steep drop in the water potential (ψ), due to water potential gradient, water enters the sieve elements and causes turgor pressure (ψp ) decrease.
c.) In sink tissues, phloem unloading leads to a lower sugar concentration in the sieve elements, generating a higher or less negative solute potential.
d.) As the water potential of the phloem rises above that of the xylem, water tends to leave the phloem in response to the water potential gradient, causing a decrease in turgor pressure in the sieve elements of the sink.
Which of the following statements of sink and source tissue is FALSE?
#Question id: 10921
#Unit 6. System Physiology – Plant
The mechanism of phloem translocation in angiosperms is best explained by which method?
#Question id: 10922
#Unit 6. System Physiology – Plant
The non-reducing sugar sucrose is most commonly translocated
in the phloem rather than reducing sugar. Why?