Read Sun and Shade Acclimation
Read the leaf's nitrogen budget to distinguish sun- and shade-acclimated plants, then practise the linked NSEB PYQ.
Photosynthesis uses light energy to make food in green plant cells; transport tissues move water and sugar where they are needed.
Track what enters, leaves and moves inside
H₂O rises from roots in xylem · sugar travels from the leaf in phloem
CO₂ enters through stomata; water arrives from roots; oxygen leaves the leaf. Sugar moves from the source leaf to use or storage sites.
Where leaf nitrogen is invested
Sun-grown leaves commonly invest a greater share of nitrogen in RuBisCO and carbon-fixation capacity. Shade-grown leaves tend to invest proportionally more in light-harvesting proteins to capture scarce light. Compare the fractions in the figure rather than relying on total nitrogen alone.
Read the chart before naming the plants
In the linked NSEB figure, M allocates 25% of leaf nitrogen to RuBisCO and 18% to light-harvesting protein; N allocates 9% to RuBisCO and 26% to light-harvesting protein. This allocation pattern, and the official final key, identify M as sun-grown and N as shade-grown.
Read pigment response to a light switch
A pigment that rises after transfer to full sun and falls after transfer to shade is a photoprotective xanthophyll-cycle pigment: here pigment II can be violaxanthin. A pigment that remains high with only modest change can be a constitutive photoprotector such as lutein: here pigment I. Read each curve's response to the switch before assigning a role. Choose A and C.
OlympIQ exam lens
- ✓Compare the RuBisCO and light-harvesting fractions separately.
- ✓Do not mistake this sun/shade comparison for a C3/C₄ comparison.
- ✓A rapid sun-induced pigment rise signals photoprotection, not necessarily light harvesting.
Similar nitrogen-allocation patterns can tempt a C3/C₄ interpretation; here the source's final answer key and the tested sun/shade pattern identify option B.
Ready to try the pattern?
100% coverage across the 2 linked questions.
Practise 2 linked questions