Biology

Plant Transport and Physiology

1,834 Questions

Access a comprehensive set of questions on plant transport mechanisms and physiological adaptations. Topics include water movement, translocation of food, and plant responses to external stimuli. These biology questions are essential for medical entrance exams and other science competitive tests.

Xylem and phloem transportTranspiration and evaporationPlant adaptationsGeotropic and phototropic responsesWater absorption by rootsRespiration in roots

Plant Transport and Physiology Questions

Multiple choice botany transpiration guttation excretion in plants long distance transport of water

Loss or excretion of water in the form of liquid droplets from the margins and tips of leaves is called

  1. Transpiration

  2. Guttation

  3. Bleeding

  4. Precipitation
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
The loss or excretion of water in the form of liquid droplets from the leaves and other parts of uninjured or intact plant is called guttation. It was first studied by Bergerstein in 18871887. All plants do not show guttation. It is restricted to about 345345 genera of herbaceous and some woody plants. Common examples are garden nasturtium, oat and other cereals, balsam, tomato, cucurbits, Guttation takes place through special structures called hydathodes. They are usually found on the margins and tips of the leaves.
So, the correct answer is 'Guttation'.
Multiple choice botany transpiration guttation excretion in plants long distance transport of water

Stomata : Transpiration : : Hydathode : ___________.

  1. Guttation

  2. Root pressure

  3. Bleeding

  4. Oozing
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
The process of exudation of liquid drops from the edges of leaves is called guttation. Usually it occurs through stomata-like pores called hydathodes. It is this process by which fully turgid plant remove extra water. The cause of guttation is mainly root pressure(when the root pressure is high and rate of transpiration is low, guttation takes place). Hydathodes are stomata-like pores, generally present at the tips or margins of leaves of those plants that grow in moist shady places(e.g., Tropaeolum). So, the correct answer is 'Guttation'.
Multiple choice botany transpiration guttation excretion in plants long distance transport of water

The process of guttation takes place

  1. When the root pressure is high and the rate of transpiration is low

  2. When the root pressure is low and the rate of transpiration is high

  3. When the root pressure equals the rate of transpiration

  4. When the root pressure as well as rate of transpiration are high
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
The process of exudation of liquid drops from the edges of leaves is called guttation. Usually it occurs through stomata-like pores called hydathodes. It is this process by which fully turgid plants remove extra water. The cause of guttation is mainly root pressure(when the root pressure is high and rate of transpiration is low, guttation takes place). Hydathodes are stomata like pores generally present at the tips or margins of leaves of those plants that grow in most shady places (e.g) Tropaeolum).
So, the correct answer is 'When the root pressure is high and the rate of transpiration is low'.
Multiple choice botany transpiration guttation excretion in plants long distance transport of water

Which one of the following is responsible for guttation?

  1. Root pressure

  2. Transpiration

  3. Photosynthesis

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

Guttation is the excretion of drops of xylem sap on the tips or edges of leaves of some vascular plants, such as grasses. In the absence of light, plant loose excess water in the form of liquid through hydathodes because most plants have their stomata closed at night. When there is a high soil moisture level, water will enter plant roots, because the water potential of the roots is lower than in the soil solution. The water will accumulate in the plant, creating a slight root pressure. The root pressure forces some water to exude through special leaf tip or edge structures, hydathodes or water glands, forming drops. Therefore, the correct answer is option A.

Multiple choice botany transpiration guttation excretion in plants long distance transport of water

Which one is true about guttation?

  1. It occurs through specialised pores called hydathodes.

  2. It occurs in herbaceous plants when root pressure is low and transpiration is high.

  3. It only occurs during the day time.

  4. It occurs in plants growing under conditions of low soil moisture and high humidity.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Guttation is the term used to refer to the phenomenon in which droplets of eater secreted from the pores in leaves of plants. It occurs through specialised pores called hydathodes. It takes place at night and in conditions of high root pressure and low transpiration. It occurs in plants growing under conditions of high soil moisture and high humidity. Thus, the correct answer is 'It occurs through specialised pores called hydathodes.'

Multiple choice blackman's principle of limiting factors photosynthesis in higher plants biology

Opening and closing of stomata is controlled by

  1. $K^{+}$
  2. $Mg^{2+}$
  3. $Ca^{2+}$

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

Potassium ions are involved in turgor movement of guard cells. Formation of organic acids like malic acid in guard cells promotes intake of potassium into the guard cells, which causes a decrease in water potential leading to intake of water by guard cells.

Multiple choice blackman's principle of limiting factors photosynthesis in higher plants biology

Which process is responsible for controlling the movement of guard cells? 

  1. Transpiration

  2. Photosynthesis

  3. Osmosis

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

Osmosis is the process which regulates the opening and closing of stomata by guard cells. When potassium ions accumulate in the cells, the water potential drops and endosmosis occurs making the cell turgid. This causes the cells to take a shape so that the stomatal pore is opened up. When water moves out of the cells, the cells become flaccid and the pore closes.

So, the correct answer is 'Osmosis'.

Multiple choice blackman's principle of limiting factors photosynthesis in higher plants biology

According to modern theory of stomatal opening, proposed by Levitt, $pH$ of guard cell can rise due to 

  1. $CO _2$ assimilation by guard cells only
  2. Active eflux of $H^+$ ion by guard cell

  3. Conversion of starch into PEP
  4. Active uptake of $K^+$ in guard cell
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Modern theory of stomatal movement is proposed by Levitt. According to it, entry of K+ ions leads to the opening of stomata during day time and exist of k+ results the closure of stomata during night time. Simultaneously, carbon dioxide assimilation occur during day time in the guard cells.

So, the correct option is ‘CO2 assimilation by guard cells only’.

Multiple choice blackman's principle of limiting factors photosynthesis in higher plants biology

Stomatal mechanism operates in response to

  1. Temperature

  2. Light

  3. Soil moisture

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

Stomatal movement are influenced by many environmental factors like temperature, light humidity, water availability (moist soil), CO$ _2$ concentration, growth hormones, minerals and pH.

Therefore, the correct answer is option D.  

Multiple choice blackman's principle of limiting factors photosynthesis in higher plants biology

Opening and closing of stomata is due to the : -

  1. Hormonal change in guard cells

  2. Change in Turgor pressure of guard cells

  3. Gaseous exchange

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

Stomata take in C02 required for the photosynthetic activity during the day.  They give out excess water released in the process of respiration during the night along with CO2. Opening and closing of stomata are controlled by the concentration of solutes in guard cells. Opening and closing of stomata take place due to turgor changes in guard cells.

  • Opening of Stomata
Solutes from neighbouring epidermal and mesophyll cell enter the guard cell lowering it osmotic potential and water potential. This lowered water potential and osmotic potential will allow movement of water in guard cells from neighbouring cells. Guard cell becomes turgid and swells in size resulting in the stomata opening due to water accumulation in them.
  • Closing of stomata
As the stomata open the solute concentration is reduced. This makes the water from the guard cell to move away into the neighbouring cell and making them flaccid with no water. They collapse against each other and results in the closing of stomata.

So, the correct answer is 'Change in Turgor pressure of guard cells'.

Multiple choice blackman's principle of limiting factors photosynthesis in higher plants biology

Which ion accumulates in the guard cells at the time of opening of stomata?

  1. P

  2. K

  3. Mg

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

It is generally well accepted that stomata opens, when guard cells become turgid due to entry of water. The water enters the guard cells from the surrounding cells, when the guard cells accumulate ions, which causes a decrease in water potential. It has been established that the ion, which accumulates in guard cells is the potassium ion. When plants are exposed to light, the guard cells accumulate large amounts of $K^+$. Light appears to stimulate active movement of $K^+$ ions from surrounding cells into the vacuoles of the guard cells. In guard cells, osmotic and hence, water potentials become very negative due to the presence of KCI, potassium malate or dipotassium malate or both. A water potential gradient is established from the accessory water movement, increased turgidity and stomatal opening.

Multiple choice blackman's principle of limiting factors photosynthesis in higher plants biology

Read the following statements and choose the correct option:
Statement -A : Potassium pump theory explains that during opening of stomata in light, ion exchange is an active process.
Statement -B : Poaceous stomata are ellipsoidal in shape.

  1. Only statement B is correct.

  2. Only statement B is incorrect.

  3. Both statement are incorrect.

  4. Both statement are correct.
Reveal answer Fill a bubble to check yourself
B Correct answer
Multiple choice blackman's principle of limiting factors photosynthesis in higher plants biology

Which is the latest explanation for the closure of stomata?

  1. Starch glucose theory
  2. Active $K^+$ ion theory

  3. ABA theory

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
  • K+ ion theory was proposed by Levitt in 1974. K ions are balanced by malate ions present in guard cells and also by taking in some Cl ions. 
  • This ion exchange occurs through the expenditure of ATP energy.
  • Plant hormone ABA acts on guard cells, which interfere with the exchange of K+ H+ ions in guard cells, results in a reverse of the reaction of the opening of stomata, hence stomata closed.
  •  Hence, Active K+ ion theory is the latest explanation for the closure of stomata.
  • So, the correct answer is  'Active K+ ion theory'.
Multiple choice blackman's principle of limiting factors photosynthesis in higher plants biology

Which of the following theory of stomatal opening and closing is given by Levitt?

  1. Theory of starch - glucose transformation
  2. Theory of active $K^+$ transport

  3. Theory of starch - sugar interconversion

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

There are three main theories about the mechanism of stomatal movement.

  1. 'Guard Cell Photosynthesis' (proposed by Schwendener, 1881).
  2. 'Starch Hydrolysis' and Starch sugar interconversion theory (proposed by Sayre, 1923 and 1926 and other contributions were made by Lloyd and Steward)
  3. Malate or potassium ion pump hypothesis (proposed by Levitt, 1974). 
According to the potassium ion pump theory, rise in pH of guard cells (due to photosynthesis and consequent decrease of carbon dioxide) causes hydrolysis of starch to form phospho enol pyruvate (PEP). PEP combines with carbon dioxide to form organic acids, like oxalic acid. The organic acids get ionised and the proton passes out of guard cells and potassium ion is actively absorbed and accumulated. This results in absorption of water from adjacent cells,  guard cells become turgid and stomata open.

Multiple choice blackman's principle of limiting factors photosynthesis in higher plants biology

Which of the following conditions help in opening of stomata?

  1. Darkness, pH 5, high $CO _2$ concentration
  2. pH 7, low $CO _2$ concentration and light
  3. pH 5, low $CO _2$ concentration and light
  4. High $CO _2$ concentration, low $K^+$ ion concentration in guard cells
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Malate or potassium ion pump hypothesis was first proposed by Levitt, 1974. According to this theory, there is a decrease of carbon dioxide in guard cells. During light exposure there is hydrolysis of starch to form phospho enol pyruvate (PEP). PEP combines with carbon dioxide to form organic acids, like oxalic acid. The organic acids get ionised and the proton passes out of guard cells and potassium ion is actively absorbed and accumulated. 

Potassium ions combine with malate and passes into small vacuoles. Chloride ions are also absorbed from outside to maintain electroneutrality. As a result of accumulation of ions there is a reduction in water potential of guard cells. The reduction in water potential causes absorption of water from adjacent cells, guard cells become turgid and stomata open.