Its defoliant effects were first noticed when it leaked from gas lights; later found to be produced by plants themselves.  

Choose the letter of the best:
A. abscisic acid
B. auxin
C. ethylene
D. cytokinin
E. gibberellin


C. ethylene

Biology & Microbiology

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Chloroplasts are composed of membranous sacs called ________ that carry chlorophyll.  Surrounding these sacs is a ground substance called ________.

A. grana; stroma B. cristae; stroma C. thylakoid; matrix D. cristae; matrix E. thylakoids; stroma

Biology & Microbiology

The heritable disorder fragile X syndrome, a major cause of intellectual disability, is caused by

A) production of enzymes that break the phosphate backbone. B) UV light. C) X-rays. D) the presence of an extra X chromosome in the sperm or egg. E) the expansion of a region of trinucleotide repeats.

Biology & Microbiology

The cell-mediated response

a. involves helper T cells. b. involves the action of antibodies to destroy invaders. c. acts only on extracellular pathogens. d. results in the production of clones of B cells. e. includes all of these.

Biology & Microbiology

Protists in freshwater systems

What will be an ideal response?

Biology & Microbiology