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6.3 Shoot Apical Meristem — Test 1
Q1. In Arabidopsis, the gene that maintains the stem-cell population at the shoot apical meristem (SAM) is:✓ WUSCHEL (WUS)
Q2. The CLAVATA3 (CLV3) peptide at the shoot meristem is perceived by which receptor?✓ CLAVATA1 (CLV1)
Q3. The WUS-CLV feedback loop maintains a stable stem-cell pool because WUS:✓ Promotes stem-cell fate and induces CLV3, which in turn restricts WUS
Q4. Loss of CLAVATA (CLV1 or CLV3) function in Arabidopsis produces a shoot meristem that is:✓ Enlarged (because WUS is no longer restricted)
Q5. Over-expression of CLV3 in Arabidopsis leads to a shoot meristem that is:✓ Smaller (stem cells are depleted)
Q6. The shoot apical meristem is the source of:✓ Leaves, stems and (later) floral organs
Q7. The central zone of the shoot apical meristem is characterised by:✓ Slowly dividing stem cells that replenish the meristem
Q8. Shoot axillary (lateral) meristems arise from the:✓ Shoot apical meristem, during leaf primordium differentiation
Q9. Leaf primordia are initiated at the:✓ Peripheral zone (flanks) of the shoot apical meristem
Q10. The positions at which successive leaves form around the stem (the leaf arrangement) is called:✓ Phyllotaxy
Q11. KNOX (e.g. SHOOTMERISTEMLESS, STM) genes are important because they:✓ Maintain the indeterminate, undifferentiated state of the shoot meristem
Q12. The phytohormone that generally promotes shoot meristem activity and cytokinesis at the SAM is:✓ Cytokinin
Q13. The WUS protein is unusual in that it:✓ Moves from the organising centre up into the stem cells to maintain them
Q14. If WUSCHEL (WUS) function is lost in Arabidopsis, the shoot meristem:✓ Terminates prematurely (stem cells are not maintained)
Q15. The shoot apical meristem is described as 'indeterminate' because it:✓ Continues to produce organs throughout the plant's life
Q16. The transition of the shoot apical meristem to a floral meristem involves a switch from indeterminate to:✓ Determinate growth (a fixed number of organs is made)
Q17. In the SAM, the boundary between the stem-cell pool and the differentiating organs is sharpened by:✓ The opposing actions of WUS (stemness) and CLV3 (restriction)
Q18. The tunica-corpus organisation of the shoot meristem refers to:✓ Outer layers (tunica) dividing anticlinally over an inner core (corpus)
Q19. Apical dominance, where the shoot tip suppresses axillary bud growth, is mediated largely by:✓ Auxin produced at the shoot apex
Q20. The shoot and root apical meristems are functionally similar in that both:✓ Contain a self-renewing stem-cell niche organised by signalling centres