IP Biology Notes: Nutrition and Transport in Flowering Plants (Upper Sec 10)

Study guide26 Nov 2025, 00:00 Z

Free IP Biology notes on leaf and root structure, photosynthesis, transpiration, and translocation for Sec 3 to Sec 4.

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Use this as a free IP Biology notes chapter on nutrition and transport in flowering plants for Year 3 to Year 4. It keeps the IP pacing while reinforcing the 6093 biology foundations most schools test through DBQs, diagrams, and practical explanations.

Status: SEAB O-Level Biology 6093 syllabus (exams from 2026) checked 2025-11-30 - scope unchanged; remains the reference for this note.

The core idea is simple: Plants make food in leaves and move water, minerals, and sugars through specialised tissues.

Use it as a working check: Xylem carries water and mineral ions upward. Phloem carries sucrose and amino acids from sources to sinks and can move in both directions.

Then go one layer deeper: Example: a dry, windy day increases transpiration, so water moves faster up xylem, but stomata may close if the plant starts losing too much water.

What you must know

Leaf: large surface area, thin, palisade mesophyll packed with chloroplasts, spongy mesophyll with air spaces, stomata for gas exchange, veins with xylem (water) and phloem (food). Xylem inner side, phloem outer in veins.
Root hair: long extension, thin wall, large surface area, close to soil particles for water/mineral uptake.
Photosynthesis: $\ce{6CO2 + 6H2O ->[light/chlorophyll] C6H12O6 + 6O2}$

Reviewed by

Ezekiel Tan·Academic Advisor (Biology)

Sources

SEAB GCE O-Level Biology (6093) syllabus (examinations from 2026)

Question clue	Process to name	Reasoning chain	Common trap
Water enters a root hair cell from soil water	Osmosis	Soil water has a higher water potential than the cell sap, so water moves through the partially permeable cell membrane into the root hair cell.	Saying water is actively transported.
Nitrate or magnesium ions enter the root hair cell	Active transport	Mineral-ion concentration may be lower in the soil than inside the root hair cell, so energy is used to move ions against the concentration gradient.	Saying all uptake happens by osmosis.
A root hair is long and narrow	Surface-area adaptation	The extension gives more cell surface in close contact with soil water and soil particles.	Saying root hairs are for photosynthesis.
A thin wall and cell membrane are shown at the soil contact surface	Short entry path	Water and dissolved ions can enter the root hair cell before moving across the cortex to the xylem.	Confusing the root hair cell with a xylem vessel.

Graph clue	What it means	Sentence to write
Rate rises when light intensity increases	Light is limiting over this part of the graph.	More light energy is available, so photosynthesis increases.
Rate stays constant even when light intensity increases further	Light is no longer the limiting factor.	Another factor, such as carbon dioxide concentration or temperature, limits the rate.
Higher carbon dioxide curve sits above a lower carbon dioxide curve	Carbon dioxide was limiting in the lower curve.	More carbon dioxide allows a higher rate until another factor limits the reaction.
Very high temperature causes the rate to fall	Enzymes are affected by heat.	Photosynthesis slows because enzymes involved in the reactions are denatured.

Factor change	Effect on transpiration	Reason to write
Higher light intensity	Usually increases	Stomata open for gas exchange, so more water vapour can diffuse out of the leaf.
Higher temperature	Increases	Water evaporates faster from mesophyll cell surfaces, and water molecules diffuse faster.
Lower humidity	Increases	The water-potential gradient between the leaf air spaces and outside air becomes steeper.
Stronger wind	Increases up to a point	Moving air removes moist air near the leaf surface, maintaining a steep diffusion gradient.
Very dry conditions causing wilting	May decrease after stomata close	Guard cells lose turgor, stomata close, and water loss is reduced even if the air is dry.

Condition	Guard-cell state	Stomatal aperture	What changes next	Common trap
Bright light and enough water	Guard cells become turgid	Stoma opens	More carbon dioxide enters for photosynthesis, but more water vapour can diffuse out	Saying light opens stomata without mentioning guard cells
Darkness	Guard cells become less turgid	Stoma closes	Less water vapour is lost, and gas exchange for photosynthesis falls	Saying stomata close only when the plant is dry
Very dry soil or wilting	Guard cells lose turgor	Stoma closes	Transpiration is reduced, but carbon dioxide entry is also reduced	Saying stomatal closure helps photosynthesis
Hot, dry, windy air before stomata close	Water evaporates and diffuses out faster	Stoma may still be open at first	Transpiration increases until water stress triggers closure	Ignoring the switch from faster loss to stomatal closure

Scenario	Source to name	Sink to name	Common trap
Daytime leaf making sugar	Photosynthesising leaf	Growing shoot, root, fruit, or storage organ	Saying xylem carries the sugar because it moves upward.
Germinating seed using stored food	Storage tissue in the seed	Growing embryo and young shoot	Assuming the leaf must always be the source.
Storage organ filling after photosynthesis	Leaf	Storage root, tuber, or fruit	Treating every underground organ as a water-only structure.
Storage organ feeding new growth	Storage root or tuber	New shoot or developing leaves	Thinking phloem can move in only one direction.

IP Biology Notes: Nutrition and Transport in Flowering Plants (Upper Sec 10)

What you must know

Sources

Detailed notes

Root hair uptake checkpoint

Photosynthesis limiting-factor checkpoint

Transpiration factor checkpoint

Guard-cell cause-effect checkpoint

Source-sink checkpoint

Xylem versus phloem transport checkpoint

Worked walkthroughs

Pitfalls and fixes

Practice drills

Quick applications

Exam cues

Next steps

Related Posts

Question clue	Tissue to name	Reason to write	Common trap
Water and mineral ions move from roots to leaves	Xylem	Dead, hollow vessels with lignin carry water upward and resist collapse under transpiration pull.	Saying xylem carries food because it is in the vein.
Sucrose or amino acids move from a leaf or storage organ to growing tissue	Phloem	Living sieve tubes and companion cells move dissolved food from source to sink using energy.	Saying phloem always moves downward.
Wilting or high transpiration changes water movement	Xylem	Faster evaporation from leaves increases the pull on the continuous water column.	Saying roots actively pump water up the stem.
Ringing removes bark and swelling appears above the ring	Phloem	Sugars made in leaves cannot pass the removed phloem, so they accumulate above the ring.	Blaming xylem if water can still move through the inner wood.