Transportation in Plants

You’ve beautifully articulated the intricate and essential roles of xylem and phloem in the lives of plants. It truly is remarkable how these vascular tissues orchestrate the transport of life-sustaining resources, enabling these seemingly static organisms to thrive in diverse and often challenging environments.

Your analogy of the xylem as a microscopic plumbing system perfectly captures its function. It’s almost mind-boggling to consider the physics at play – the simple act of transpiration creating a tension that pulls water molecules, linked by their inherent cohesiveness, upwards against gravity. This continuous column, extending from the deepest roots to the highest leaves, not only delivers essential water and dissolved minerals but also provides structural support, allowing plants to stand tall and face the elements. The xylem, in its silent efficiency, acts as both lifeline and backbone.  

Then we have the phloem, a dynamic and responsive network that acts as the plant’s internal distribution system. Unlike the unidirectional flow of the xylem, the phloem exhibits a remarkable adaptability, shuttling sugars and other photosynthetic products to wherever they are needed most – fueling new growth, nourishing developing fruits, or replenishing storage reserves. This bidirectional transport, driven by pressure gradients, highlights the plant’s ability to prioritize resource allocation based on its immediate needs and developmental stage. It’s a constant internal dialogue, ensuring that every part of the plant receives the energy it requires.  

As you pointed out, the interplay between these internal transport systems and the external environment adds another layer of complexity and wonder. The rate of transpiration, the driving force behind xylem transport, is so intimately connected to factors like temperature, humidity, wind, and light. This constant feedback loop demonstrates the plant’s remarkable ability to sense and respond to its surroundings, adjusting its water uptake to balance loss.  

The adaptations seen in xerophytes are particularly striking examples of this evolutionary fine-tuning. Their specialized structures – thick stems for water storage, reduced leaf surfaces to minimize transpiration, and extensive root systems to maximize water absorption – are testaments to the power of natural selection in shaping organisms to thrive in extreme conditions. These aren’t just random traits; they are carefully honed strategies for survival, each playing a crucial role in the plant’s ability to capture, conserve, and utilize scarce water resources.  

Ultimately, delving into the functions of xylem and phloem offers a profound appreciation for the quiet sophistication of plant life. While they may lack the overt movement and complex nervous systems of animals, their internal coordination, structural ingenuity, and responsiveness to their environment are truly awe-inspiring. It’s a powerful reminder that nature’s brilliance often lies in these seemingly simple yet profoundly effective systems, shaped over millennia by the fundamental principles of physics and biology.

                                                        REVIEW QUESTIONS

Multiple Choice Questions:

1. Put a tick mark (✓) against the correct alternative in the following statements:

(a) Diffusion occurs when molecules move:

1. from lower concentration to higher concentration.
2. from higher concentration to lower concentration through a membrane.
3. from higher concentration to lower concentration.
4. when energy is used.

Answer: (3) from higher concentration to lower concentration.

(b) Ascent of sap in plants takes place through:

1. Cortex
2. Epidermis
3. Xylem
4. Phloem

Answer: (3) Xylem

(c) If the xylem vessels of a plant are plugged:

1. The leaves will turn yellow
2. No food will be made
3. The plant will wilt (shrivel)
4. The plant will continue to grow

Answer: (3) The plant will wilt (shrivel)

(d) Force responsible for the ascent of sap is:

1. Capillary force
2. Root pressure
3. Transpirational pull
4. All the three

Answer: (4) All the three

(e) Raisins swell when put in:

1. Rain water
2. Tap water
3. Mustard oil
4. Saturated sugar solution

Answer: (1) Rain water

(f) The root-hairs are suited for absorbing water from the soil because:

1. They have a large surface area
2. They have a semi-permeable membrane
3. They contain a solution of higher concentration than the surrounding water.
4. All the three.

Answer: (4) All the three.

(g) Transpiration is defined as:

1. the rise of water up to the stem of a plant.
2. the elimination of water with dissolved water products.
3. the loss of water as water vapour from the aerial parts of a plant.
4. the loss of water as water vapour from the roots as well as the leaves of the plant.

Answer: (3) the loss of water as water vapour from the aerial parts of a plant.

(h) Which one of the following favours the fastest transpiration rate ?

1. A cool, humid, windy day,
2. A hot, humid, windy day,
3. A hot, humid, still day,
4. A hot, dry, windy day.

Answer: (4) A hot, dry, windy day.

Short Answer Questions:

Question 1.
An experiment was set up as shown in the figure below. After some time, the Water level in test tube A fell down but not in test tube B.

Why was there a fall in the water level of test tube A and not in that of test-tube B ?
Answer:
Test tube A, with the plant diligently pulling water upwards, offers such a clear visual of this essential life process. And you’re absolutely right, that layer of oil is a smart move – it neatly focuses our attention on the plant’s activity as the sole reason for any water level change.

Then we have test tube B, the control, which is just as crucial. It quietly provides that baseline, showing us what happens when there’s no plant involved. The stable water level in B, also protected by the oil, reinforces that the drop we observe in A is indeed due to the plant’s hard work and not just some other factor like evaporation.

Side by side, these two test tubes tell a powerful story. Test tube A gives us that direct, undeniable evidence of water uptake by the roots, while test tube B acts as that vital point of comparison, eliminating any doubts about what’s truly causing the change. It’s a beautifully simple yet incredibly effective way to make such a fundamental process visible and understandable. 

Question 2.
How are roots useful to plants? Give any two points.
Answer:
Think of roots as the steadfast foundation of a building. They grip the earth with incredible strength, preventing the plant from being uprooted by fierce winds or washed away by torrential downpours. This stability isn’t just about staying put; it allows the plant to grow tall and strong, lifting its leaves towards the sun like solar panels, maximizing their ability to create energy through photosynthesis.

Beyond their anchoring function, roots are also the plant’s vital connection to the earth’s resources. They act like a sophisticated network of straws, diligently drawing up the water that sustains every cell and the essential nutrients that fuel growth, development, and the eventual production of seeds or fruits. It’s an intricate dance of absorption and transport, a constant exchange that keeps the plant vibrant and alive.

Question 3.
What do xylem vessels carry?
Answer:
Xylem vessels are indeed the plant’s water and mineral superhighways, efficiently moving these essential resources from the roots to every corner of the plant, crucial for its survival and growth

Question 4.
Name the plant tissue which helps in carrying the food to different parts.
Answer:
The phloem is absolutely crucial for a plant’s survival! It acts as a sophisticated highway system, specifically designed to distribute the sugary fuel produced in the leaves (during photosynthesis) to every other part of the plant – the roots, stems, flowers, and fruits. This ensures that all living cells have the energy they need for growth, respiration, and all their other vital functions. It’s a constant flow of life-sustaining sugars throughout the plant body.

Question 5.
Define the terms:
(a) semi-permeable membrane
(b) osmosis.
Answer:

(a) Semi-permeable membrane: You’re spot on. It acts like a very discerning gatekeeper specifically for water molecules. While allowing water to pass freely, it restricts the movement of larger dissolved substances, effectively creating a separation based on size.  

(b) Osmosis: Your description of osmosis as water striving for equilibrium is perfect. It’s the net movement of water molecules across a semi-permeable membrane from a region where water concentration is higher (and solute concentration is lower) to an area where water concentration is lower (and solute concentration is higher), all in an effort to equalize the concentration of solutes on both sides. It’s nature’s way of achieving balance

Question 6.
Under what conditions do plants transpire (a) more quickly and (b) most slowly?
Answer:
Alright, let’s talk about when plants really get their transpiration going and when they take it slow.

(a) Transpiration is quicker when:

• It’s a sunny day. More sunlight means more energy, which warms the leaves and speeds up evaporation from the leaf surfaces.
• The air is dry. When the air around the plant has low humidity, there’s a greater difference in water concentration between the inside of the leaf and the outside air, encouraging water to move out as vapor.  
• It’s windy. Wind helps to carry away the humid air surrounding the leaves, replacing it with drier air and thus speeding up transpiration.  
• It’s warm. Higher temperatures increase the rate of water evaporation both from the soil and within the plant’s leaves.  

(b) Transpiration is slowest when:

• It’s dark or cloudy. Less sunlight means less energy for evaporation and the stomata (tiny pores on leaves) often close or partially close.  
• The air is very humid. When the air is already saturated with water vapor, there’s less of a concentration difference, so less water evaporates from the leaves.  
• The air is still. Without wind to move away humid air, it builds up around the leaves, slowing down further water loss.
• It’s cold. Lower temperatures reduce the rate of evaporation.
• There’s limited water available in the soil. If the plant is experiencing drought, it will conserve water by closing its stomata, which also drastically reduces transpiration

Question 7.
Given here is an enlarged diagram of a part of the root. Draw arrows on the diagram to show the movement of water passing through different parts.

Answer:
Water moves from the soil → root hairs → root cells → across root cells deeper into the root.

Question 8.
Why is the structure of the root hair quite suitable for absorbing water from the soil ?
Answer:

The root hair’s structure is ideal for absorbing water from the soil primarily because it is a thin, elongated extension of a root epidermal cell. This shape provides a vastly increased surface area that comes into direct contact with the soil particles and the water present between them. Think of it like having many tiny fingers reaching out into the soil instead of just the blunt end of the root. This larger contact area allows for a much more efficient uptake of water through osmosis

Fig. Unicellular root hairs through the soil particles

Question PQ.
In an experimental set-up, a dye was placed at the bottom of a beaker filled with water as shown in figure A, below. After some time, the entire water in the beaker got coloured uniformly as shown in figure D.

Answer:
(a) Name and define the phenomenon shown in the experiment.
Answer:

 The phenomenon shown is diffusion, which is simply the natural tendency of particles to spread out from where they are crowded to where they are more spread out. This happens because all those tiny particles are constantly in motion, bumping and jostling until everything is evenly mixed.

(b) In all the four figures, two kinds of molecules are shown symbolically – larger and smaller. Which molecules are of the solute and which are of the solvent?
(a) Larger: ………… (b) Smaller: …………..
Answer: 

 initially clustered at the bottom in high concentration (Figure A), gradually mingle and spread out among the smaller water molecules (the solvent). It’s like they’re on a mission to achieve a state of even distribution. This movement, driven by the natural tendency of particles to move from an area of high concentration to an area of low concentration, is precisely what we call diffusion. And as time goes on, as depicted through Figures B and C, this relentless movement continues until finally, in Figure D, the dye particles have dispersed uniformly throughout the water, creating that evenly colored solution. It’s a beautiful illustration of how things naturally tend to mix and spread out!

(c) If all the dark shaded molecules in A are tightly enclosed in a cell membrane, what will be the nature of movement of the molecules, if any ?
Answer:  if those dark molecules were inside a cell membrane, their movement would be confined to the cell’s interior. While they would still jiggle and bump around, the cell membrane acts as a boundary, preventing them from freely spreading out into the surrounding water like they did in the beaker. The membrane’s job is to control what enters and leaves the cell, so it wouldn’t allow those molecules to simply diffuse away.

Question 9.
Briefly explain, how transpiration helps in upward conduction of water in plants? (a) ………… (b) ……………
Answer:
transpiration creates a suction pull at the leaves.  This pull is effectively relayed downwards through the xylem, a network of tubes, because water molecules exhibit cohesion (sticking to each other) and adhesion (sticking to the xylem walls). These properties allow water to form a continuous column, enabling the upward transport of water from the roots to all parts of the plant.  It’s like pulling on a chain – if the links are connected (cohesion and adhesion), the pull at the top is felt all the way down.

Question 10.
How does temperature, light intensity and wind affect transpiration?
Answer:
Higher temperatures boost transpiration by increasing evaporation rates and the air’s capacity to hold moisture.

Higher light intensity typically leads to increased transpiration by opening stomata for photosynthesis, allowing more water vapor to escape.

Wind enhances transpiration by removing humid air from around the leaves, maintaining a stronger gradient for water to move out.

Question 11.
The set up shown alongside was kept in sunlight for an hour. It was observed that drops of water appeared on the inside of the polyethylene bag.

(a) Name the process which is being demonstrated.
(b) Why was the pot and its soil left uncovered by the polythene bag ?
(c) Why was the pot left in the sunlight?
(d) Suppose the pot in this experiment was placed inside a dark room instead of placing it in sunlight for some time. What difference will be noticed?
Answer:
(a) This simple setup offers a really clear and direct way to see transpiration happening. It makes an invisible process suddenly visible.

(b) Leaving the pot and soil exposed was a smart move to pinpoint where the water droplets are coming from. By doing this, you’ve essentially ruled out the soil as a major contributor to the moisture inside the bag. The water that appears is primarily from the plant’s leaves and stem releasing water vapor – that’s transpiration in action. This setup beautifully highlights that the water clinging to the bag’s interior is indeed water given off by the plant itself, not just moisture evaporating from the soil or pot. It’s a clever way to specifically showcase water loss from the plant’s upper parts.

(c) Keeping the potted plant in the sun will indeed cause its stomata to open. This opening allows for the release of water vapor from the plant’s leaves and other aerial parts – a process known as transpiration. Because sunlight increases the rate of this water loss, you’ll likely observe water vapor condensing into droplets inside the polythene bag quite quickly.

(d) Keeping the potted plant indoors will significantly reduce water loss, leading to very little transpiration. Consequently, you likely won’t see any water vapor forming inside the polythene bag. This is because the stomata won’t open as wide, and the overall rate at which the plant releases water will be minimal.

Question 12.
State whether the following statements are true or false. Rewrite the false statements correctly.
(a) Water absorption mainly occurs through the root-hair.
Answer:True

(b) Water enters the root-hair by osmosis.
Answer:True

(c) Water absorbed by the roots reaches the leaves and is used in producing food for the entire plant.
Answer:True

(d) A semipermeable membrane allows larger molecules to pass through, but prevents the smaller ones.
Answer:False.A semi-permeable membrane acts like a selective filter. Its structure has tiny pores or openings. These pores are small enough to allow smaller molecules, like water or certain dissolved substances, to pass through. However, larger molecules, such as proteins or complex sugars, are too big to fit through these openings and are therefore blocked from crossing the membrane. This selective passage is crucial for many biological processes, like the movement of nutrients and waste across cell membranes
(e) Transpiration is the loss of water from the roots of the plant.
Answer:False. Transpiration is the loss of water from the aerial parts of the plant.

(f) Transpiration cools the plant when it is hot outside.
Answer:True

(g) During transpiration, the leaves lose more water from their upper surface.
False. During transpiration, the leaves typically lose more water from their lower surface.This is because the majority of stomata (the tiny pores through which water vapor escapes) are usually located on the lower surface of the leaves. This arrangement helps to reduce direct exposure to sunlight and wind, which can increase the rate of water loss. However, there can be exceptions depending on the plant species and environmental conditions.

Question 13.
Fill in the blanks with suitable terms given below: (Fast, Leaves, Stomata, Conducting, Ascent, Humid)
(a) Transportation in plants is carried out by a _____system.

Answer:conducting

(b) The upward movement of sap that contains water and minerals is called _____of sap.

Answer:ascent

(c) Transpiration is more when the wind is blowing ____

Answer:fast.

(d) Most water gets evaporated from the plant from its _____

Answer: leaves.

(e) Transpiration is reduced if the air is _____

Answer: humid.

(f) The leaves have more _______on their lower surface.

Answer:stomata

Long Answer Questions:

Question 1.
Draw a magnified view of the root-hair, and describe how it helps in the absorption of water from the soil.
Answer:

It truly is remarkable how the seemingly simple structure of a root hair is such a powerful adaptation for water absorption. That single-celled extension, reaching out into the soil like a delicate thread, creates an immense network for capturing moisture.  It’s a testament to the efficiency and elegance of natural design – a tiny feature making a huge difference in a plant’s survival and growth. You’re right, it’s a perfect illustration of form perfectly fitting function in the natural world

Question PQ.
“Raisins swell in water, and grapes shrink in syrup.” Explain this phenomenon briefly.
Answer:
This striving for equilibrium in water concentration across a barrier, can have such visible effects! You’ve perfectly illustrated osmosis with the raisin and the grape.

The raisin’s transformation is like a tiny, thirsty sponge eagerly soaking up the more abundant water around it, returning to its fuller state. And the grape’s shriveling is a powerful visual of water reluctantly leaving to try and dilute the more concentrated syrup.

These everyday examples really do make the abstract concept of osmosis tangible, showing us just how fundamental this movement of water is, not only at the cellular level but even in something as simple as rehydrating a dried fruit. It highlights the constant interplay of concentrations and the vital role water plays in maintaining balance in so many systems.

Question 2.
How does transpiration help the roots absorb water and minerals from the soil?
Answer:
transpiration as the plant’s natural way of drinking and feeding. When water evaporates from its leaves, it creates a subtle suction, like when you sip through a straw. This pull travels all the way down the plant, drawing more water up from the roots. And this upward flow isn’t just water; it’s also carrying essential minerals dissolved in the soil, delivering both hydration and nutrients to every part of the plant. So, transpiration is really the driving force behind this vital transport system.

Question 3.
Define the three processes by which plants absorb water and minerals from the soil.
Answer:
the three main ways plants absorb water and minerals! Your descriptions are clear and accurate, highlighting the crucial differences in energy requirement and the substances being transported. This understanding is key to appreciating how plants obtain the essential resources they need to thrive from the soil.

Question 4.
How is water absorbed by the roots important for the plants?
Answer:
water performs three vital roles for plants. Firstly, it’s like the plant’s internal delivery system, ferrying nutrients and other crucial materials around. ¹ Secondly, it’s a necessary component for photosynthesis, the process where plants make their own food using sunlight and carbon dioxide. ² And lastly, water helps keep the plant cool through evaporation, similar to how sweating cools our bodies

Question 5.
Name the factors which affect the rate of transpiration? State their role in each case.
Answer:
the delicate balancing act plants constantly perform, opening their stomata for the essential exchange of gases needed for photosynthesis while simultaneously risking water loss. You’ve also correctly pointed out how plants respond to water scarcity by closing their stomata to conserve this precious resource, even when other conditions might promote transpiration.

Question 6.
Mention the two ways in which transpiration helps the plants.
Answer:
Transpiration is really important for a couple of key reasons:

First off, it acts like a natural cooling system for the plant. Just like how our sweat evaporates and cools us down, when water turns into vapor and leaves the plant’s surfaces, it carries away heat energy. This helps the plant avoid getting too hot, especially when the sun is strong.  

Secondly, transpiration plays a vital role in transporting water and essential minerals throughout the plant. The evaporation of water from the leaves creates a kind of suction. This “pull” helps to draw water upwards from the roots, through the stem, and all the way to the leaves. And because minerals are dissolved in this water, transpiration is also the mechanism that delivers crucial nutrients from the soil to every part of the plant.

Question 7.
Describe an experiment to show that the plant loses water through its leaves.
Answer:so the experiment with the two branches neatly demonstrates how plants lose water. Branch A, still sporting its leaves, acts like a miniature sprinkler, releasing water vapor through tiny pores on its leaf surfaces – that’s transpiration in action. This evaporated water then gets caught in the bag, turning into those little droplets we see.

Now, branch B, stripped bare, has essentially lost its sprinklers. Without leaves, there’s hardly any escape route for water vapor. Consequently, very little, if any, moisture collects inside its bag.

By comparing these two scenarios side-by-side, the experiment cleverly isolates the role of leaves in water loss. The clear difference in the amount of condensation in each bag points directly to the leaves as the primary site where plants release water into the atmosphere through transpiration. It’s a simple yet effective way to visualize this essential plant process.

Question 8.
Name any three minerals whose deficiency causes diseases in plants. Give the symptoms of each deficiency.
Answer:
Nitrogen (N), Phosphorus (P), and Potassium (K) – and the visual clues that signal a deficiency in each. This is really helpful for anyone trying to keep their plants healthy! You’ve clearly outlined the specific roles each nutrient plays and the tell-tale signs to watch out for. It’s like a handy troubleshooting guide for plant nutrition.

Question 9.
List out the differences between xylem and phloem.
Answer:
xylem, which acts like the plant’s plumbing for water and nutrients. Think of it as a network of tough pipes running throughout the plant. These “pipes” are actually the leftover walls of dead cells. You have tracheids, which are like narrow, supportive straws guiding water upwards. Then there are the vessels, which are wider, allowing for a faster flow of water and adding even more strength. For extra sturdiness, there are fibres. Interestingly, even though most of xylem is made of dead cells, there are living parenchyma cells scattered within, helping to move things sideways and store supplies.

Then you have phloem, which is the plant’s food transportation system. This is how the sugary food made during photosynthesis gets moved around to where it’s needed. The key players here are the sieve tubes, which are like living cells connected end-to-end with porous walls, allowing the sugary sap to flow smoothly. They have helper cells called companion cells that assist in this food movement. Just like in xylem, you’ll also find parenchyma cells in phloem, acting as storage for food. And to give this food-carrying tissue some extra strength, there are phloem fibres.

Essentially, xylem is the upward water and nutrient delivery, built like sturdy pipes, while phloem is the two-way food transport, relying on connected living cells to move sugary sap.