Given below are some of the statements that regulate the sucrose loading mechanism;

A) The solute potential or, more likely, the turgor pressure of the sieve elements

B) Sucrose concentration in the apoplast

C) The available number of symporter protein molecules

Possible observation given on how to avoid regulation;

i) increase in sieve element turgor above a certain threshold would lead to a compensatory increase in loading

ii) High sucrose concentrations in the apoplast would increase phloem loading

iii) SUT1 transporter mRNA and protein have been lower after 15 hours of darkness than after a light treatment. These data suggest that the concentration of SUT1 transporter molecules could regulate loading

iv) Decrease in sieve element turgor below a certain threshold would lead to a compensatory increase in loading

v) The transporter mRNA and protein high in darkness than lower in the light treatment

Which of the following combinations represents correct observation?

#Question id: 11732

#Unit 6. System Physiology – Plant

Cytokinins are defined as compounds that have biological activities similar to those of trans-zeatin. These activities include the ability to do the following:

a) Induce cell division in callus cells in the presence of an auxin

b) Promote bud or root formation from callus cultures when in the appropriate molar ratios to auxin

c) promote senescence of leaves

d) Promote expansion of dicot cotyledons

Which one of the following activities are incorrect?

#Question id: 11733

#Unit 6. System Physiology – Plant

The synthetic cytokinin compounds that have not been identified in plants, these are;

#Question id: 11734

#Unit 6. System Physiology – Plant

Some molecules act as cytokinin antagonists, which are able to block the action of cytokinins that is

#Question id: 11735

#Unit 6. System Physiology – Plant

In cytokinin biosynthesis is the addition of the isopentenyl side chain from DMAPP to an adenosine moiety. The plant and bacterial IPT enzymes differ substrate used;

a) the bacterial enzyme utilizes AMP

b) the plant enzyme appears to utilize AMP

c) the bacterial enzyme utilizes both ADP and ATP

d) the plant enzyme appears to utilize both ADP and ATP

#Question id: 11736

#Unit 6. System Physiology – Plant

Many plant tissues contain the enzyme cytokinin oxidase, which cleaves the side chain, except

#Question id: 11737

#Unit 6. System Physiology – Plant

Cytokinins have been shown to have effects on many physiological and developmental processes, including____

a) Leaf senescence

b) Apical dominance

c) Gametophytic  development

d) Vascular development

e) Breaking of bud dormancy

f) Causing bud dormancy