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6.5 Leaf Development — Test 1
Q1. Because plant cells have rigid walls and cannot migrate, leaf shape in the primordium is determined mainly by:✓ The planes of cell division (and oriented expansion)
Q2. Leaf primordia are initiated at the:✓ Peripheral (flank) zone of the shoot apical meristem
Q3. The adaxial-abaxial (upper-lower) polarity of a leaf is important because it:✓ Sets up different upper and lower tissues and the flat blade
Q4. The adaxial (upper) identity of a leaf is specified by genes such as:✓ PHABULOSA/PHAVOLUTA (HD-ZIP III)
Q5. The microRNA miR166 patterns the leaf by:✓ Restricting adaxial (HD-ZIP III) gene expression to the upper side
Q6. Trichomes are:✓ Epidermal hair-like outgrowths on leaves and stems
Q7. A GLABRA1 (GL1) mutant Arabidopsis plant shows:✓ Fewer or no trichomes
Q8. In trichome patterning, the TRY (TRYPTYCHON) protein acts as a:✓ Negative regulator that inhibits trichome fate in neighbouring cells
Q9. The flat blade of a typical leaf develops from the juxtaposition of:✓ Adaxial and abaxial domains
Q10. Leaf veins (vascular tissue) form in a pattern guided largely by:✓ Canalised auxin flow (with PIN proteins)
Q11. Programmed cell death (PCD) in leaf and plant development is responsible for forming:✓ Tracheary elements (xylem), and structures like leaf lobes/perforations
Q12. Leaf longevity is increased in ethylene-insensitive Arabidopsis mutants (e.g. ein2), showing that ethylene:✓ Promotes leaf senescence
Q13. During leaf senescence, the early events include:✓ Re-differentiation of chloroplasts and remobilisation of nutrients
Q14. Xylogenesis (wood/xylem formation) is an example of plant development that depends on:✓ Programmed cell death of the differentiating cells
Q15. The change in leaf shape during the juvenile-to-adult phase transition is associated with:✓ Differential methylation and changes in regulatory genes (e.g. miR156/SPL)
Q16. The juvenile-to-adult vegetative transition in Arabidopsis is controlled by a decline in:✓ miR156 (which allows SPL genes to rise)
Q17. KNOX gene expression must be switched OFF in incipient leaf primordia because KNOX:✓ Maintains the indeterminate meristem state, which leaves must escape
Q18. Compound (dissected) leaves versus simple leaves often differ because of:✓ Differences in KNOX gene re-expression in the leaf primordium
Q19. Leaf development illustrates a general plant principle that organ shape arises from:✓ Controlled cell division orientation and expansion within fixed cell walls
Q20. Leaf trichome and root-hair patterning both use similar logic in which a cell's fate depends on:✓ Lateral inhibition and cell position relative to neighbours