Biology

Plant Growth and Hormones

727 Questions

Plant growth and hormones is a vital topic in biology that covers the physiological effects of different plant regulators like auxins, gibberellins, and cytokinins. These concepts are frequently tested in various general science sections of competitive exams. Practicing these questions helps clarify complex mechanisms like vernalisation, senescence, and tropism for test takers.

Abscisic acid effectsCytokinin functionsAuxins and tropismPlant tissue cultureSenescence in plantsNatural plant hormones

Plant Growth and Hormones Questions

Multiple choice biology movement and locomotion in living organisms movements in plants coordination in plants tropic and nastic movements in plants

The movement of plant organs in response to the force of gravity is called as

  1. Hydrotropism

  2. Geotropism

  3. Heliotropism

  4. Phototropism
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Gravitropism (also known as geotropism) is a turning or growth movement by a plant or fungus in response to gravity. It is a general feature of all higher and many lower plants as well as other organisms.Therefore, the correct answer is option B.

Multiple choice biology movement and locomotion in living organisms movements in plants coordination in plants tropic and nastic movements in plants

Phototropism of stem and root are due to 

  1. Differential hormonal effect

  2. Epinasty and hyponasty

  3. Effect of light

  4. Graviperception
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Phototropism in stem and root are due to differential phytohormonal effect. Stem grows positively phototropic. Roots grow negatively geotropic. Auxin is responsible for apical dominance and positive phototropism by stem.

Multiple choice biology movement and locomotion in living organisms movements in plants coordination in plants tropic and nastic movements in plants

Phototropism in shoots is attributed to or phototropic movements are due to

  1. Auxin

  2. Gibberellins

  3. Cytokinin

  4. Abscisic acid
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Auxin is a plant hormone that plays important role in phototropism, growth movement in response to light. It promotes cell elongation. It is unequally distributed in the plant cells. It is transported towards the shady side and thus present in higher concentration. However, less auxin is transported towards the side exposed to light. Due to this, the plant grows more on the shaded side and bend in the direction of the light source. It shows positive phototropism where faster cell elongation is seen on the shaded side and less on the illuminated side. 

Thus, the correct answer is option A.

Multiple choice biology movement and locomotion in living organisms movements in plants coordination in plants tropic and nastic movements in plants

Phototropism is because of unequal distribution of auxin under the influence of unilateral (one sided) illumination as auxin

  1. Moves from illuminated side to shaded side

  2. Synthesis is checked on illuminated side

  3. Destroyed on illuminated and not on shaded side

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Auxin is a plant hormone that plays important role in phototropism, growth movement in response to light. It promotes cell elongation. It is unequally distributed in the plant cells. It is transported towards the shady side and thus present in higher concentration. However, less auxin is transported towards the illuminated side. Auxin synthesis is inhibited on illuminated side. It moves from the illuminated side to shaded side. Due to this, the plant to grow more on the shaded side and bend in the direction of the light source. It shows phototropic response where faster cell elongation is seen on the shaded side than on the illuminated side. 

Thus, the correct answer is option D.

Multiple choice biology movement and locomotion in living organisms movements in plants coordination in plants tropic and nastic movements in plants

More concentration of auxin in horizontally placed plants, under the influence of gravity, occurs in

  1. Upper side

  2. Lower side

  3. Both upper and lower side

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Auxin is a plant hormone that plays important role in the growth of stem and roots to gravity. Gravitropism is a plant growth response to gravity. Root shows positive gravitropism and shoot shows negative gravitropism. When plant is placed horizontally, more concentration occurs in lower side of the root and stem. This stimulates stem elongation and thus stem grows upwards. This inhibits root elongation and thus root grows downwards. 

Thus, the correct answer is option B.

Multiple choice movement in plants living world of plants - plant physiology biology

Which of the following movements in plants is not related to changes in auxin levels?

  1. Nyctinastic leaf movements

  2. Movement of roots towards soil

  3. Movement of sunflower tracking the direction of sun

  4. Movement of shoot towards light
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Movements in nyctinasty plants are not related to auxin levels. 

Nyctinasty is a type of tactic movement of a plant where the movement of plants organs like leaves occur in rfesponse to day and light and thus known as sleep movements. (Circardian rhythm) Eg in case of Acasia torcuosa, the movement of leavs occur horizontal during  the day and vertical during the night. 
It is the movement of the plants' organs like roots towards the soil, sunflower tracking towards the sun which are regulated by the Auxin levels. So, the correct option is'Nyctinasty leave movements'. 

Multiple choice movement in plants living world of plants - plant physiology biology

In hyponasty, there is increased growth on

  1. Shaded side

  2. Illuminated side

  3. Lower surface

  4. Upper surface
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Nastic movements are responses of plant parts to stimuli. Epinasty is the downward bending of a leaf resulting from greater growth of the upper side than of the lower side. Due to more growth on the upper side, the flower will open due to epinasty. The hyponasty is an upward bending of leaves resulting from increased growth on the lower surface.

Thus, the correct answer is option C.

Multiple choice movement in plants living world of plants - plant physiology biology

Stimulus in Mimosa pudica travels in the form of

  1. Auxin

  2. Hormone

  3. Alcohol

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The dropping of leaves of Mimosa pudica shows thigmonastic movement upon touching. This dropping is due to the action potential which travels through the plant. The stimulus travels in the form of signaling molecules and hormones. These includes intracellular calcium, reactive oxygen species, ethylene hormone.

So, the correct answer is B 'Hormone'

Multiple choice botany biotechnology and its applications biotechnology in agriculture gm crops transgenic organisms

Which of the following attributes can be improved in ornamental plants?

  1. Regulation of flowering

  2. Weed control

  3. Promotion of vegetative growth

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Ornamental plants are known for the decorative purposes in gardens and landscape design projects, as houseplants, for cut flowers and specimen display.
The regulation of flower can be improved in ornamental plants through physical alteration of day length or modification of hormone biosynthesis and metabolism.
Weeds can be controlled by resistance to a broad spectrum herbicide like glyphosate which would allow the protection of young plants from weed seedlings in new areas and prevent damage from spot- spraying of weeds in established beds.
The vegetative growth of the ornamental plants can be promoted by using various growth regulators.
So, the correct answer is option D.
Multiple choice botany taxonomy and systematic botany taxonomy and systematics systematics of living world kingdom plantae plant taxonomy classification of biodiversity

Consider the following statements.
a. In climacteric fruits, ethylene stimulates its own production.
b. Gibberellin present in a healthy stem causes some of the new cells to differentiate as phloem.
c. Loss of turgor in leaves stimulates the production of abscises acid.
Which of the statements given are correct?

  1. $1$ and $2$ only
  2. $2$ and $3$ only
  3. $1$ and $3$ only
  4. $1, 2$ and $3$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Statement a is correct because climacteric fruits exhibit a surge in respiration accompanied by autocatalytic ethylene production. Statement c is also correct because water stress and loss of turgor in leaves trigger the synthesis and accumulation of abscisic acid to close stomata. Statement b is incorrect because gibberellins do not cause cells to differentiate specifically into phloem.

Multiple choice botany taxonomy and systematic botany taxonomy and systematics systematics of living world kingdom plantae plant taxonomy classification of biodiversity

In some flowering plants, the requirement of long day length or low temperature treatment for flowering can be effectively substituted by _______________.

  1. Morphactins

  2. Coumarins
  3. $2, 4$-D

  4. Gibberllins
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Gibberellins are plant hormones that can successfully substitute for long-day photoperiod requirements or low-temperature cold treatments (vernalization) to induce flowering in various plant species. They help overcome these environmental triggers artificially. Other compounds like 2,4-D are synthetic auxins used mainly as herbicides.

Multiple choice biology plant growth other plant hormones cytokinins, ethylene and abscisic acid plant hormones

Which one of the following responses of plants to growth hormones is true for ethylene?

  1. Increase in cell elongation

  2. Decrease in the formation of female flowers

  3. Increase in ripening of fruits

  4. Decrease in abscission of flowers
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Ethylene affects fruit - ripening. Normally, when the seeds are mature, ethylene production increases and builds - up within the fruit, resulting in a climacteric event just before seed dispersal. The nuclear protein 'Ethylene Insensitive 2' is regulated by ethylene production, and in turn, regulates other hormones including ABA and stress hormones.

Multiple choice biology plant growth other plant hormones cytokinins, ethylene and abscisic acid plant hormones

Ethylene is mainly responsible for

  1. Formation of flower

  2. Formation of root hairs

  3. Ripening of fruits

  4. Formation of fruit
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

There are five classes of naturally occurring plant growth regulator. These are auxins, gibberellins, cytokinins, abscisic acid and ethylene. Ethylene is also called as ripening hormone as it is responsible for ripening of fruits. Fruit ripening is accompanied by increase rate of respiration. Due to increased respiration, complex carbohydrates are broken down into simpler sugars and cell wall becomes soft. It inhibits cell division. It is also involved in abscission of leaves, fruits and flowers.

Thus, the correct answer is option C.

Multiple choice biology plant growth other plant hormones cytokinins, ethylene and abscisic acid plant hormones

Which response of growth hormone is true for ethylene?

  1. Decrease in flower abscission

  2. Decreases in femaleness

  3. Increase in fruit ripening

  4. Increase in cell elongation
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Ethylene is a gaseous plant hormone. It is also called as ripening hormone as it increases ripening of fruits. Fruit ripening is accompanied by increase rate of respiration. Due to increased respiration, complex carbohydrates are broken down into simpler sugars and cell wall becomes soft. It inhibits cell division. It is also involved in abscission of leaves, fruits and flowers.

Thus, the correct answer is option C.