When the bark of a tree is removed in a circular fashion all around near its base, it gradually dries up and dies because
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- AWater form soil cannot rise to aerial parts
- BRoots are starved of energy
- CTree is infected by soil microbes
- DRoots do not receive oxygen for respiration
Show answer
Answer: (B) Roots are starved of energy
The answer is (b) — the roots are STARVED OF ENERGY (food).
When bark is removed in a complete ring around a tree (called GIRDLING or RING-BARKING), you cut through the PHLOEM — the tissue that transports food (sugars produced by photosynthesis in the leaves) DOWNWARD from leaves to roots.
Here's the chain of events:
(1) Bark removed → phloem is cut → food can't travel down to roots.
(2) XYLEM (inner wood) is NOT cut, so water can still travel UP from roots to leaves — the tree looks fine initially.
(3) Leaves continue photosynthesis but food accumulates above the ring (you may see swelling above the cut).
(4) Roots gradually STARVE because they receive no food → they stop absorbing water and minerals.
(5) Eventually the entire tree dies.
Why not other options?
- (a) Water CAN still rise (xylem is intact — it's deeper than bark).
- (c) Soil microbes don't specifically attack just because bark is removed.
- (d) Roots get oxygen from soil, not from bark.
Key concept: Phloem (in bark) carries food DOWN. Xylem (in wood) carries water UP. Girdling cuts phloem → roots starve.
Girdling cuts the phloem tissue in bark that transports food downward from leaves to roots, while leaving the xylem intact so water can still move upward initially.
The question tests whether students understand the difference between phloem (food transport) and xylem (water transport) - a fundamental concept in plant biology that UPSC uses to check if students know how plants actually function versus superficial knowledge.
Plant Transport Tissues: Xylem & Phloem
Science And Technology bark phloem xylem
Plant Transport Tissues: Xylem & Phloem Functions
Phloem transports food (sugars) downward from leaves to roots
Xylem transports water and minerals upward from roots to leaves
Phloem is located in bark, xylem is in inner wood
Cutting phloem starves roots of energy while water transport continues initially
Two-Way Highway
Plants have two separate transport systems working simultaneously. Xylem moves water and dissolved minerals from soil upward to leaves for photosynthesis. Phloem moves the food produced by photosynthesis (mainly sugars) downward to feed roots, stems, and growing parts.
Xylem vs Phloem
Feature | Xylem | Phloem |
|---|---|---|
Location | Inner wood (deeper tissue) | Bark (outer tissue) |
Transport Direction | Upward (roots → leaves) | Downward (leaves → roots) |
What it carries | Water + minerals from soil | Food (sugars) from photosynthesis |
Cell type | Dead hollow tubes | Living cells with pores |
Driving force | Transpiration pull | Source-sink pressure |
Why Location Matters
Phloem sits in the bark because it needs to be close to the leaf-producing areas. When you remove bark completely around a tree, you cut through all the phloem but leave the deeper xylem intact. This creates a deadly blockage in food transport while water transport continues normally.
Plant Vascular System
Source: Britannica — Vascular system | Botany, Xylem, Phloem, Importance ... · www.britannica.com
Girdling (Ring-Barking) Process
Science And Technology bark removed circular fashion dries up dies
Girdling: How Removing Bark Kills Trees
Girdling = removing bark in complete ring around tree trunk
Cuts phloem (food transport) but leaves xylem (water transport) intact initially
Roots starve because no food reaches them from photosynthesis
Tree dies gradually as starved roots stop functioning
The Deadly Ring
Girdling (also called ring-barking) involves removing bark in a complete circle around the tree trunk. This cuts all phloem tissues that transport food from leaves to roots, while leaving the inner xylem wood intact.
How Girdling Kills Trees
%%{init: {"flowchart": {"wrappingWidth": 460}}}%%
flowchart TD
s1["`**Bark removed in ring**
**All phloem cut**, xylem remains intact`"]
s2["`**Food transport blocked**
Sugars from photosynthesis **cannot reach roots**`"]
s3["`**Water transport continues**
Tree appears **healthy initially** - leaves stay green`"]
s4["`**Food accumulates above cut**
**Swelling** may appear above the girdled area`"]
s5["`**Roots begin starving**
**No energy** for root metabolism and growth`"]
s6["`**Root function fails**
Starved roots **stop absorbing** water and minerals`"]
s7["`**Tree dies completely**
Water shortage kills leaves, **entire tree perishes**`"]
s1 --> s2
s2 --> s3
s3 --> s4
s4 --> s5
s5 --> s6
s6 --> s7Question Connection
This question tests understanding that roots need continuous food supply from photosynthesis. Even though water can still move up (xylem intact), the tree dies because roots are starved of energy - making option B correct.
Photosynthesis & Food Distribution
Science And Technology
How Plants Distribute Food from Photosynthesis
Leaves produce food (glucose) through photosynthesis using sunlight
All plant parts need this food for energy - roots, stems, flowers, fruits
Phloem distributes food from leaves to non-photosynthetic parts
Roots cannot survive without food from leaves - they don't photosynthesize
Food Factory & Distribution
Leaves are food factories that produce glucose through photosynthesis. But roots, stems, and other parts cannot make their own food - they depend entirely on leaves. The phloem acts as a distribution network carrying sugars to every living part of the plant.
Plant Food Distribution System
# Food from Photosynthesis
## Source: Leaves
- Capture sunlight
- Produce glucose
- Convert CO₂ + water
## Transport: Phloem
- Living sieve tubes
- Pressure-driven flow
- Bidirectional when needed
## Sinks: Non-photosynthetic parts
- **Roots** (energy for absorption)
- **Stems** (growth & support)
- **Fruits** (development)
- **Storage organs** (bulbs, tubers)Why Roots Need Constant Food
Root metabolism: Roots need energy for active absorption of water and minerals from soil
Root growth: New root cells require glucose for cell division and elongation
Maintenance: Existing root cells need energy for basic cellular processes and repair
No backup: Unlike stems, roots have no stored food reserves and cannot photosynthesize
Symbiotic relationships: Root bacteria (like nitrogen-fixers) also need plant-provided sugars
Common UPSC Plant Physiology Traps
Science And Technology
Plant Transport: Common UPSC Misconceptions
Trap: Thinking water transport is blocked first - but xylem (water) is deeper than phloem (food)
Trap: Assuming soil microbes cause death - but girdling kills through starvation, not infection
Trap: Believing roots need oxygen from bark - but roots get oxygen from soil air spaces
Trap: Confusing which direction each tissue transports - xylem UP, phloem DOWN
Trap: Thinking trees die immediately - but starvation is gradual as stored energy depletes
Key Distinctions UPSC Tests
Immediate vs delayed effects: Water transport continues initially, food blockage kills gradually
Depth of tissues: Bark contains phloem (outer), wood contains xylem (inner)
Root dependencies: Roots need food from leaves more critically than oxygen from bark
Transport directions: Never confuse upward water flow with downward food flow
Cause vs symptom: Starvation is the cause, drying is the final symptom
Answer Strategy
For plant transport questions, always ask: 'What is actually cut?' and 'Which direction does it normally transport?' In girdling, phloem is cut, blocking downward food movement to roots. This makes root starvation the primary cause of death.