Home
Class 12
BIOLOGY
Darwing discovered that canary grass c...

Darwing discovered that canary grass coleoptile bends towards light only when .

A

It is 5 cm long

B

The seedling is growing in blue light

C

Coeloptile tip is intact and exposed to light

D

Cooler nights

Text Solution

Verified by Experts

The correct Answer is:
C
Promotional Banner

Topper's Solved these Questions

  • PLANT GROWTH AND DEVELOPMENT

    AAKASH SERIES|Exercise EXERCISE -II (GIBBERELLINS )|12 Videos

  • PLANT GROWTH AND DEVELOPMENT

    AAKASH SERIES|Exercise EXERCISE -II (CYTOKININS )|26 Videos

  • PLANT GROWTH AND DEVELOPMENT

    AAKASH SERIES|Exercise EXERCISE - I (VERNALIZATION )|2 Videos

  • PHOTOSYNTHESIS IN HIGHER PLANTS

    AAKASH SERIES|Exercise Exercise - III|27 Videos

  • PRINCIPLES AND PROCESSES

    AAKASH SERIES|Exercise Exercise - III (Previous AIPMT/NEET Questions)|26 Videos

Similar Questions

Explore conceptually related problems

As shown in the figure, two particle each of mass m tied at the ends of a light string of length 2a are kept on a frictionless horizontal surface. When the mid-point (P) of the string is pulled vertically upwards with a small but constant force F, the particles move towards each other on the surface. Magnitude of acceleration of each particle, when the separation between them becomes 2x is

A green plants bends towards the source of light when exposed to the light on only one side . Which of the following is the best explanation of the phenomenon ?

What causes a green plant exposed to the light , on only one side , to bend towards the source of light as it grows ?

Amines are less reactive in substitution reactions. Their reactivity is much lesser than alcohols and alkylflourides towards substitution. Protonation of the amino group makes it a better leaving group, but not nearly as good a leaving group as a protonated alcohol. Protonated amino groups cannot be displaced by OH^(-) because it would react immediately with the acidic hydrogen which would convert it in to a poor nucleophile. The leaving group in quartenary ammonium ion has about the same leaving tendency as a protonated amino group but does not have acidic hydrogen. The reaction of a quartenary ammonium ion with hydroxide ion is known as Hoffmann elimination reaction. The leaving group is tertiary amine. Since a tertiary amine is only a moderately good leaving group, the reaction requires heat. The carbon to which the tertiary amine is attached is designated as alpha carbon. When the hydroxide ion starts to remove a beta H from a quartenary ammonium ion, the leaving group does not immediately start to leave because a tertiary amine is not a good leaving group. As a result, a partial negative charge builds up on the carbon from which the proton is removed. Which of the following statements are true regarding Hoffmann elimination ?

Amines are less reactive in substitution reactions. Their reactivity is much lesser than alcohols and alkylflourides towards substitution. Protonation of the amino group makes it a better leaving group, but not nearly as good a leaving group as a protonated alcohol. Protonated amino groups cannot be displaced by OH^(-) because it would react immediately with the acidic hydrogen which would convert it in to a poor nucleophile. The leaving group in quartenary ammonium ion has about the same leaving tendency as a protonated amino group but does not have acidic hydrogen. The reaction of a quartenary ammonium ion with hydroxide ion is known as Hoffmann elimination reaction. The leaving group is tertiary amine. Since a tertiary amine is only a moderately good leaving group, the reaction requires heat. The carbon to which the tertiary amine is attached is designated as alpha carbon. When the hydroxide ion starts to remove a beta H from a quartenary ammonium ion, the leaving group does not immediately start to leave because a tertiary amine is not a good leaving group. As a result, a partial negative charge builds up on the carbon from which the proton is removed. The compounds 'C' in question number 31 on heating with moist silver oxide gives

Amines are less reactive in substitution reactions. Their reactivity is much lesser than alcohols and alkylflourides towards substitution. Protonation of the amino group makes it a better leaving group, but not nearly as good a leaving group as a protonated alcohol. Protonated amino groups cannot be displaced by OH^(-) because it would react immediately with the acidic hydrogen which would convert it in to a poor nucleophile. The leaving group in quartenary ammonium ion has about the same leaving tendency as a protonated amino group but does not have acidic hydrogen. The reaction of a quartenary ammonium ion with hydroxide ion is known as Hoffmann elimination reaction. The leaving group is tertiary amine. Since a tertiary amine is only a moderately good leaving group, the reaction requires heat. The carbon to which the tertiary amine is attached is designated as alpha carbon. When the hydroxide ion starts to remove a beta H from a quartenary ammonium ion, the leaving group does not immediately start to leave because a tertiary amine is not a good leaving group. As a result, a partial negative charge builds up on the carbon from which the proton is removed. Which of the following statements is correct?

Dr. F.Went note that if coleoptile tips were removed and planced on agar for one hour , the agar would produce a bending when placed on one side of freshly -cut coleoptile stumps. Of what significance is this experiment ?