Plants move molecules to long distances, much more than animals without possessing any circulatory system. The water that is absorbed by the roots has to reach every part of the plant. The process of photosynthesis by leaves is necessitated to move across all parts even the tips of the roots that are buried deep in the soil. Substances that are transported in flowering plants are mineral nutrients, water, organic nutrients, and plant growth regulators. Through cytoplasmic streaming supplemented by active transport and diffusion, substances can move over short distances. However, over longer distances, transportation is carried out by the vascular system – the xylem and the phloem. This is referred to as translocation. Continue reading to get insights on transportation in plants.
Very Short Answer Type Questions
Q.1. Addition of urea to flowering plant so as to grow faster in earthen pot results in the death of the plant after a while. What can be the cause?
A.1. Due to exosmosis, the plant dies. Water gradually tends to move out of the plant cell as the solution outside is a hypertonic solution whereas the plant cell is hypotonic. This causes plasmolysis of the cells of the roots and ultimately, the death of the plant.
Q.2. The direction and rate of Osmosis depends upon ________
A.2. It depends upon both the concentration gradient and pressure gradient
Q.3. Water absorption by dry seeds from soil rises the ______, hence aiding seedlings to appear out of the soil.
A.3. The seed materials imbibe water which propels the seedlings out of the soil hence the seed swells and imbibition pressure rises within the seeds enabling seed germination.
Q.4. What is solute potential and water potential?
A.4. The potential energy of water is considered to be as the water potential. It is also regarded as a measure of the difference between the potential energy of pure water and a given sample of water. The lowering magnitude of water potential because of the dissolution of solute is known as solute potential.
Q.5. Explain how almost all the water moves into the root?
A.5. The apoplast pathway causes water to flow in the root as the cortical cells are generally loosely arranged which provide no resistance to the water that moves through the mass flow. It occurs due to cohesive and adhesive properties exhibited by water. Symplast pathway is also attributed to the movement of molecules of water within the root.
Q.6. Name a molecular movement that is highly selective requiring special membrane proteins without needing any energy.
A.6. Facilitated diffusion
Short Answer Type Questions
Q.1. How does the analysis of the exudate enable one to detect minerals and the form in which they are assembled in the plant?
A.1. Chemical analysis on the exudate(plant sap) can help us understand the form and identity of mineral nutrients that are transported in the plants as the exudate is a mixture of inorganic and organic compounds such as ions, amino acids, sugars, etc. For example, Sulphur in sulphate ion forms, nitrogen is absorbed and transported as NO2 and NO3
Q.2. Name a method that can be used to increase the life span of cut plants in a vase.
A.2. By quickly transferring them into water its lifespan can be increased as air will immediately shift into the tissue that conducts water and fill the cell. In addition, supplying elements and nutrients in varying concentrations can increase its life span. Cytokine, a hormone is sprayed or can be dipped in its solution to delay plant senescence.
Q.3. Does the rate of transpiration in different species of a plant cultivated in the same area differ in a particular time? Support your answer.
A.3. The rate of transpiration is governed by several factors. If two species have the same morphology and are related, then the rate of transpiration is dependant on external factors such as humidity, temperature, wind velocity, light intensity, etc.
Q.4. Explain why the intracellular levels of K+ in animal cells is higher than the extracellular levels.
A.4. The ion channels can be closed or open, i.e, they are ‘gated’. The Na+, K+, ATPase generate an imbalance in the charge across the plasma membrane by passing 3Na+ out of the cell for each 2K+ ion carried within causing the inside negative relative to outside. The membrane is referred to as polarized. Hence intracellular levels of K+ are higher.
Q.5. Why cut pieces of beetroot produce colour in hot water and not in cold water?
A.5. It is because the beetroot pigment dissolves and disperses immediately in hot water as hot temperature facilitates leakage of the plasma membrane and discharge of beetroot pigment.
Long Answer Type Questions
Q.1. Do plants require to adjust the solute types that arrive at the xylem? Name the molecules that assist in adjusting. How is the regulation of the type and quantity of solutes that reach the xylem brought about by the plants?
A.1. Yes, adjustment is required. The end dermal cells possess the transport proteins which aid in regulating and adjusting the solute movement. Since soil minerals are present as charged particles with less concentration in comparison to the roots, they all cannot be transported passively across the cell membranes of the root hairs. Hence through passive and active processes minerals are transported to the xylem. On arriving at xylem, they are further transported towards the sink through the transpiration stream. The mineral ions at the sink region are unloaded through active uptake by receptor cells and diffusion. A few mineral ions that that move often through xylem are:
- Nitrogen travels in plants as inorganic ions NO2 and NO3 but much of the nitrogen moves in the form of amino acids and related organic compounds
- Minerals ions are frequently remobilized specifically from older senescing pats. Leaves that are old and dying export most of its mineral content to younger leaves. Likewise, before leaf fall in deciduous plants, minerals are eliminated from other parts. A few elements that are readily mobilized are sulphur, phosphorous, potassium and nitrogen.
Q.2. State differences between permanent and temporary wilting.
A.2. Wilting refers to the loss of turgidity of leaves and the other soft aerial parts of a plant that causes folding, dropping and rolling of non-woody plants. It usually takes place when the rate of water loss is higher than the rate at which it is absorbed.
|Temporary Wilting||Permanent Wilting|
|Loss of turgidity causes temporary drooping of leaves observed during noon time. It occurs when the rate of transpiration exceeds the water absorption due to the shrinking of roots. It recovers on being treated with water around the root hairs in the soil. Plants regain their growth.||Loss of turgidity permanently in leaves and other plant parts. Rate of transpiration is higher than the rate of absorption but the difference is seen below a critical level. Wilting here does not recover as the cells do not obtain the turgidity even upon water addition and environment. The plant dies eventually.|
Q.3. How are halophytes able to display a high precell pressure compared to the atmospheric pressure.
A.3. Halophytes require soil with a high concentration of salts to grow. In the cytoplasm, there is an accumulation of salts due to which the osmotic concentration in the cytoplasm is increased that causes the entrance of water into the cells. Hence, the turgor pressure in halophytes cells is higher in comparison. Two steps are adapted by halophytes to restrict it:
- In vacuoles, they gather salts away from the cytoplasm
- Presence of salt-secreting glands to eliminate excess salts
Q.4. Classify the following into semipermeable membrane (S.P) and selectively permeable (S.L)
a) Animal Bladder
d) Parchment membrane
e) Egg membrane
A.4. The classification is shown below:
|Semipermeable Membrane||Selectively Permeable|
|Parchment membrane||Animal Bladder Plasmalemma Tonoplast Egg membrane|
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