There are at least three different types of companion cells in the minor veins of mature, exporting leaves. Which of the following statements about these companion cells is CORRECT?

 a.) transfer cells are transport sugars enter the apoplast during the movement of sugars from mesophyll cells to sieve elements. Transfer cells transport sugars from the apoplast to the symplast of the sieve elements and companion cells in the source.

 b.) the numerous mitochondria in companion cells may supply energy as ATP to the sieve elements

 c.) Ordinary companion cells can function in either symplastic or apoplastic short-distance transport in source leaves, depending in part on plasmodesmatal frequencies

 d.) Intermediary cells, by contrast, function in symplastic transport of sugars from mesophyll cells to sieve elements

#Question id: 11607

#Unit 6. System Physiology – Plant

How the active gibberellin GA1 is inactived by?

a)  By hydroxylation remove GA20 from the biosynthetic pathway by converting it to GA1

b) conversion to GA8 by a hydroxylation on carbon 2

c) By hydroxylation remove GA20 from the biosynthetic pathway by converting it to GA29

#Question id: 11608

#Unit 6. System Physiology – Plant

Which of the following  growth hormone  promote stem growth and were discovered in relation to the “foolish seedling disease” of rice?

#Question id: 11609

#Unit 6. System Physiology – Plant

All of gibberellins are tetracyclic diterpenoid acids, but only a few of which, have intrinsic biologically active gibberellins these are__

#Question id: 11610

#Unit 6. System Physiology – Plant

Environmental factors such as photoperiod and temperature can alter the levels of active gibberellins by affecting gene transcription for specific steps in the biosynthetic pathway such as;

a) Promotion of germination by light has been shown to be due to increases in GA1 levels resulting from a light-induced increase in the transcription of the gene for GA3ox, which converts GA20 to GA1

b) level of GA20-oxidase occurs in the highest amount in shoot tips and elongating stems, is increased under long-day conditions.  The fact that GA 20-oxidase is the enzyme that converts GA53 to GA20

c) Giving cold treatment  of Thlaspiarvense and a return to high temperatures, the ent-kaurenoic acid is converted to GA9, the most active gibberellin for stimulating the flowering response

d) Potato plants overexpressing the GA20ox gene showed tuberization, whereas transformation with the antisense gene for GA20ox inhibited tuberization

Which of the following from the given above statements is correct?

#Question id: 11611

#Unit 6. System Physiology – Plant

Given below are names of phytohormones in column I and their associated features/effects/ functions in column II.

Which of the following combination from the above statements is  correct? 

#Question id: 11612

#Unit 6. System Physiology – Plant

AMO-1618, which blocks GA biosynthesis at the cyclization step, what would be the A, B and C represents. where, the control shows no inhibitor;