Transport in Plants: Highlights from NCERT Biology for NEET 2022

A quick revision via highlights from NCERT Biology boosts your NEET preparation. Students can find below highlights of Transport in Plants as per the NEET 2022 Syllabus. Transport in Plants is amongst the NEET 2022 important chapters. Aspirants of NEET can utilise the highlights given below for last-minute revisions. Highlights from NCERT Biology– Transport in Plants include all the vital biology concepts frequently asked in the NEET exam. Go through the important terms, definitions, functions, and much more in an easy-to-comprehend manner to enable every aspirant to outperform in the NEET 2022 exam and an outshining NEET 2022 Result.

Means of Transport

There are various means of transport for water and nutrients in plants depending upon the type of movement taken into consideration. 

Small distance transport: 

• Diffusion
• Cytoplasmic streaming
• Active transport

Translocation or transport over long distances:

• Through vascular transport via xylem and phloem

The transportation of nutrients and water in plants has a set direction. It can be

1. Unidirectional: In rooted plants, the transport of water and minerals from roots to the stems via xylem is unidirectional. 
2. Bidirectional: Organic and mineral nutrients have multidirectional transport.

Important Terms 

• Simple Diffusion

Definition: The random movement of substances from their higher concentration region to their lower concentration region. 

The movement of substances takes place along the concentration gradient, and thus it does not require any energy expenditure. It is a passive means of transport.

Simple diffusion depends on the following aspects:

• Concentration gradient
• Size of molecules
• Temperature
• Pressure
• Surface area available for diffusion

• Facilitated Diffusion

Definition: The movement of hydrophilic molecules with the support of transmembrane proteins is called facilitated diffusion.

Facilitated diffusion favours the movement of large particles as well. However, the process is sensitive to inhibitor molecules.

The movement of substances takes place along the concentration gradient, and thus it does not require any energy expenditure. It is a passive means of transport.

• Active Transport/ Uphill Transport

Definition: The movement of molecules of substances from a lower concentration region to a higher concentration region against the concentration gradient, requiring energy expenditure, is called active transport.

• Porins 

Porins are membrane proteins forming large pores in the outer membranes of certain organelles such as plastids and mitochondria as well as some bacteria, allowing molecules of small size to pass through. 

• Aquaporins

They are membrane proteins that serve as channels for water transfer and sometimes small solutes across membranes.

• Symport

It is the transport process of two different molecules in the same direction as a carrier molecule.  

• Antiport

It is the transport process of two different molecules in the opposite direction through a membrane.

• Uniport

The movement of molecules of a substance across a membrane independent of other molecules is called uniport.

Comparison of Different Transport Systems

Plant Water Relations

Here are some important concepts from NCERT Biology for NEET 2022 on Transport in Plants.

• Water Potential (ѱw)

The difference between the energy of water in a system and the free energy of water molecules in pure water is referred to as water potential (ѱw).

The water potential of pure water at standard temperature is zero. 

• Solute Potential (Ψs)

Solute potential or osmotic potential is the magnitude of lowering the water potential of a solution from pure water due to the dissolution of solute. So, more solute molecules mean lower solute potential.

• Pressure Potential

The pressure potential is the positive pressure developed in a system due to the osmotic entry of water into it.

Relationship between water, solute, and pressure potential:

Ψw = Ψp + Ψp 

• Osmosis

The movement of water molecules from their higher concentration to their lower concentration region via a semipermeable membrane is called osmosis.

• Endosmosis

The movement of water molecules inside a cell when placed in a hypotonic solution or water is called endosmosis. The cell becomes turgid.

• Exosmosis

When placed in a hypertonic solution, the movement of water molecules from inside a cell to the outside solution is called exosmosis. The cell becomes flaccid.

• Hypotonic Solution and Hypertonic Solution

The solution with lower solute concentration and lower osmotic pressure is hypotonic. 

A solution with higher solute concentration and higher osmotic pressure is called hypertonic.

• Osmotic Pressure

The minimum pressure required to be applied to a solution for preventing the inward flow of water or its pure solvent via a semipermeable membrane is called osmotic pressure.

• Turgor Pressure

The cell fluid exerts turgor pressure on the cell membrane, which keeps that cell membrane pushed towards the cell wall. It is also called hydrostatic pressure.   

• Plasmolysis

When a cell is placed in a hypertonic solution, water moves out of the cell. The cell membrane and protoplasm shrink away from its cell wall, and the phenomenon is called plasmolysis. 

• Flaccid

A cell is flaccid when water flows in and out of the cell in equilibrium. The plasma membrane of a flaccid cell is not pressed tightly against the cell wall. A cell becomes flaccid when it is placed in an isotonic solution.

• Turgid

A cell is turgid when placed in water or hypotonic solution, and water molecules enter the cell via endosmosis, making it distended. The cell membrane pressed tightly against the cell wall. A turgid cell has turgor pressure. 

• Imbibition

The phenomenon of adsorption of any liquid or water by cells of a solid substance is called imbibition. No solution is formed in the process without creating a solution.

Long Distance Transport of Water

Mass flow or bulk flow system is the movement of substances in mass or bulk from the sites of adsorption or production to the areas of consumption or storage due to pressure differences between the two regions. 

Bulk flow takes place through a positive hydrostatic pressure gradient or negative hydrostatic pressure gradient.

Pathway of Water Flow 

1. Apoplast pathway: The movement of water from the root hair to the xylem via walls of intervening cells and not by crossing any membrane or cytoplasm describes the apoplast pathway. The movement takes place through bulk or mass flow.
2. Symplast pathway: When water enters the cell sap of root hair, it moves into the underlying cortex cells via plasmodesmata. This water moves through the endodermis by the symplast ( inner side of plasma membrane), and thus the pathway is termed the symplast pathway. The presence of Casparian strips ensures a blockage of the movement of water and minerals from one side to the other via the cell wall route.

Important Terms

• Root Pressure

The root cells’ hydrostatic pressure developed due to the endosmosis of water and minerals that help in the ascent of sap is called root pressure.

• Guttation

Guttation is the oozing out of a cell’s water from hydathodes due to positive xylem pressure.

• Ascent of Sap

The movement of absorbed water and dissolved substances upward in the form of a solution/ sap from the plant’s roots to the aerial parts is called the ascent of sap.

Transpiration 

The loss of water via stomata from aerial parts of the plant is called transpiration. It depends on

• Temperature
• Light
• Humidity
• Wind speed
• Number and distribution of stomata
• Per cent of open stomata
• Water status of the plant
• Canopy structure.

Transpirational pull: The water loss via transpiration creates a water deficit in the mesophyll cells. They absorb water from the adjacent cell creating a pull (cohesion-tension transpiration pull) for water along the channel. The upward pull is called transpirational pull.

Uptake and Transport of Mineral Nutrients

• Some minerals move in from the soil to the epidermal cell cytoplasm with the help of specific proteins in the root hair cell membranes.  
• Endodermal cells have transport proteins that control the quantity and the types of solutes that will enter the xylem.
• The lateral pathway of absorbed mineral ions from the epiblema to the xylem is as follows:

epiblema →cortex →endodermis →pericycle → xylem

Phloem Transport

Flow from Source to Sink

The source-sink relationship describes the food production site as the source and where it is stored /needed as a sink.

The Pressure Flow or Mass Flow Hypothesis

It is the mechanism of translocation of sugars from source to sink. It is bidirectional, and we can summarise it as follows:

• The leaves produce glucose by photosynthesis. It is converted to sucrose.
• Sucrose → companion cells → into the living phloem sieve tube cells via active transport
• The loading of the source produces a hypertonic condition in the phloem, and water from the adjacent xylem vessels moves into the phloem by osmosis. 
• Osmotic pressure develops in the phloem, and the sap moves to lower pressure areas. 
• When it reaches the sink, the osmotic pressure is reduced by active transport of the sucrose out of the phloem sap to the cells that require sugar energy.

Bottomline

Plant Physiology has a weightage of 13% for the NEET 2022 exam. Transport in Plants covers a major section of this unit. Therefore, students must ensure that they are well-versed in every chapter topic. All students must check out the NEET 2022 Exam Pattern and understand how the questions are formulated. Moreover, we encourage NEET 2022 aspirants to take a few NEET Mock Tests 2022 to boost their preparation. Solving NEET Previous Year Question Papers is also helpful to ace your understanding and self-evaluation of the crucial biology concepts for NEET 2022.

FAQs

1. What is the importance of Plant Physiology for the NEET exam?

Plant physiology is one of the most important units in the NEET exam. It carries up to 8 to 12 questions in NEET and has a weightage of 13%. Moreover, this topic of biology is comparatively easier and provides students with an opportunity to boost their NEET 2022 rank. Therefore, students must get well-versed with Plant Physiology concepts in the NEET 2022 syllabus and facilitate their exam preparation. Practising sample questions of this chapter can give you an edge over the competition.

2. Is NCERT Biology enough for NEET 2022 preparation?

NCERT Biology is a complete source of knowledge for NEET 2022 aspirants. It explains the important biology concepts and has questions for practice. Students must thoroughly prepare every line in the NCERT Biology to ace the stiff competition. Moreover, the questions provided in the book are often a part of NEET examinations. Students can check out NCERT Solutions for Class 11 Biology and NCERT Solutions for Class 12 Biology if they have confusion regarding the answers. 

3. How should I revise Transport in Plants for NEET 2022?

Students must follow a strategic plan to revise all the biology chapters for NEET 2022.

• It is best to begin by deciding which chapters require more attention or the ones that are your weaknesses. 
• Refer to your notes for revision 
• Understand the concepts rather than adopting rote memorisation
• Students must select only 1-2 good books for reference during revision.  
• Practice NEET Previous Year Question Papers once you have completed a chapter/ unit 

4. How do mock tests assist in NEET 2022 exam preparation?

NEET Mock tests 2022 can help students in the following ways:

• They get acquainted with the question paper pattern and mark distribution.
• Help them evaluate their readiness for the NEET 2022 exam.
• Taking a mock test allows students to enhance their speed and accuracy.
• Mock tests make students comfortable with the exam, thereby reducing anxiety.
• Most importantly, aspirants can get a proper exam analysis report from subject experts on current preparation level, weaknesses, strengths, and overall improvement.