Question 1

Question 1Define the following terms:(a) Phytohormones(b) Tropism(c) Clinostat(d) Apical dominance(e) Parthenocarpy(f) Abscission(g) Heliotropism

Accepted Answer

(a) Phytohormones — Phytohormones or plant hormones are naturally occurring small organic molecules.(b) Tropism — Response or orientation of a plant to certain stimulus that acts with greater intensity from one direction to another is called tropism.(c) Clinostat — Clinostat is a mechanical device that rotates at a slow speed to demonstrate geotropism.(d) Apical dominance — The phenomenon of the suppression of growth of lateral buds by apical buds is called apical dominance.(e) Parthenocarpy — Development of fruits without fertilisation is called parthenocarpy.(f) Abscission — Abscission is the shedding of various parts of a plant such as leaves, buds, flowers and fruits.(g) Heliotropism — The phenomenon in which the young flower heads follow the sun across the sky as it moves from east to west direction is called heliotropism.

Question 2

Question 3Differentiate between:(a) Thigmotropism and geotropism(b) Positive and negative tropism(c) Stimulus and response(d) Phototropism and chemotropism

Accepted Answer

(a) Difference between thigmotropism and geotropismThigmotropismGeotropismDirectional growth movement of a plant part in response to the touch of an object.Directional growth movement of a plant part in response to gravity.Example — Plants such as sweet peas, Cuscuta and vines have tendrils which coil around other plants in response to one sided contact or touch.Example — Growth of roots of plants in downward direction.(b) Difference between positive and negative tropismPositive tropismNegative tropismMovement of plant part towards the direction of the stimulus is called positive tropism.Movement of plant part against the direction of the stimulus is called negative tropism.Example — Shoots show positive phototropism and grow in the direction of sunlight.Example — Roots show negative phototropism and grow against the direction of sunlight.(c) Difference between stimulus and responseStimulusResponseChange in the internal or external environment of an organism is called a stimulus.Resulting action or movement caused by the stimulus is called a response.Example — In phototropism, sunlight is the stimulus.Example — In phototropism, the bending of the shoot is the response to the stimulus of sunlight.(d) Difference between phototropism and chemotropismPhototropismChemotropismIt means the movement in response to the stimulus of light.It is the phenomenon of growth or movement of a plant part towards the source of nutrients or chemicals.Example — Growth of shoots of plants in upward direction.Example — Growth of pollen tube towards sugar and peptones of the female gametophyte.

Question 3

Question 7Apical dominance is influenced by :GibberellinsEthyleneCytokininsAuxins

Accepted Answer

AuxinsReason — The phenomenon of the suppression of growth of lateral buds by apical buds is called apical dominance and it is seen due to presence of auxin in apex region of plant.

Question 4

Question 8The growth movement of plant parts which occurs due to touch stimulus is called:HeliotropismChemotropismHydrotropismThigmotropism

Accepted Answer

ThigmotropismReason — The growth movement of plant parts which occurs due to touch stimulus is called thigmotropism. For example, coiling of tendrils to their support.

Question 5

Question 9The instrument which can be used to demonstrate geotropism is:ManometerThermostatClinostatBarometer

Accepted Answer

ClinostatReason — Geotropism can be demonstrated in laboratory by using Clinostat. It has two set-ups with planted pots. One is static while the other rotates.

Question 6

Question 10The hormone which accelerates senescence (ageing) and abscission of leaves is :IAAGA3ABAGA1

Accepted Answer

ABAReason — Abscisic Acid (ABA) is the hormone which accelerates senescence (ageing) and abscission of leaves. It is a growth inhibitor.

Question 7

Question 2Complete the following sentences:(a) Growth of root towards water is ............... .(b) ............... hormone inhibits apical dominance.(c) ............... and ............... induce chemotropism of angiosperms and gymnosperms.(d) ............... of sweet peas exhibit thigmotropism.(e) ............... is also called as "stress hormone".

Accepted Answer

(a) Growth of root towards water is hydrotropism .(b) Cytokinins hormone inhibits apical dominance.(c) Sugars and peptones induce chemotropism of angiosperms and gymnosperms.(d) Tendrils of sweet peas exhibit thigmotropism.(e) Abscisic acid is also called as "stress hormone".

Question 8

Question 4Study the diagrams given below and answer the following questions.(a) Name the structures shown as X and Y in the figures (A) and (B), respectively.(b) Write the functions performed by the structures X and Y.(c) Name the phenomenon depicted and define it.(d) How do the structures X and Y differ from each other?(e) Give examples of the plants which show the said phenomenon.

Accepted Answer

(a) X → Stem tendrils, Y → Leaf tendrils.(b) Stem tendrils (X) and leaf tendrils (Y) enable the plant to climb up a support.(c) Thigmotropism is the phenomenon depicted. It is the growth movement of plant parts in response to touch stimulus.(d) Stem tendrils (X) arise from the stem while leaf tendrils (Y) arise from the leaf of the plant.(e) Sweet Pea, Vines and Cuscuta.

Question 9

Question 5Given below are the figures showing some kinds of tropic movements in plants. Study the same and answer the following questions:(a) Which one of these figures is correct? Give reason in support of your answer.(b) Name the kind of movements shown by the root system and the shoot system. Define each.(c) What are the two stimuli which affect root system and shoot system positively? Name them.(d) Which of the following stimuli affect the growth of root strongly?GravityWater(e) Draw a neat and labelled diagram of the longitudinal section of a pistil showing chemotropism in an angiospermic plant.

Accepted Answer

(a) Figure A is correct as it shows roots growing towards gravity and shoot growing away from gravity.(b) Root shows positive geotropism and shoot shows negative geotropism.Positive geotropism is defined as movement of plant towards earth's gravity. For example, roots show positive geotropism.Negative geotropism is defined as movement of plant away from gravity. For example, shoot shows negative geotropism.(c) Root system — Gravity     Shoot system — Light(d) WaterReason — For roots, water is a more effective stimulus than gravity.(e) Below diagram shows chemotropism in a pistil:

Question 10

Question 6The figure given below depicts a kind of tropic movement in plants. Study the same and answer the following questions.(a) What kind of a movement is shown in figure. Define it.(b) How does this movement differ from geotropism?(c) Name the stimulus responsible for thigmotropism. Give one example of a plant showing thigmotropism.(d) Name one stimulus which gives a positive response for the roots but negative response for the shoot.(e) Draw a neat and labelled diagram of the part of plant showing leaf tendril. Name the plant.

Accepted Answer

(a) Phototropism.It is defined as the movement in response to the stimulus of light.(b) Stimulus for phototropism is light whereas for geotropism it is gravity.(c) Touch is the stimulus for thigmotropism.Example — The tendrils of sweet pea plant start coiling around the support in response to touch.(d) Gravity(e) Sweet pea plant shows thigmotropism. The labelled diagram showing leaf tendril is given below:

Chemical Coordination in Plants

Descriptive Type

Multiple Choice Type

Short Answer Type

Structured Application Skill Type