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6.4 Root Development — Test 1
Q1. In plants, lateral roots are initiated from the:✓ Pericycle
Q2. A mutation in the SCARECROW (SCR) gene disrupts radial root patterning, producing roots that:✓ Lack the layer that normally forms both cortex and endodermis
Q3. The PLETHORA (PLT) transcription factors are important for:✓ Specifying the root stem-cell niche and delimiting meristematic/elongation zones
Q4. The group of cells that generates the root vascular tissues, including the pericycle, is the:✓ Procambium
Q5. The stele initials in the root apical meristem give rise to:✓ The root vascular system, including the pericycle
Q6. If a mutation causes MORE lateral roots to form, the wild-type gene product most likely acts as a:✓ Negative regulator of lateral root formation
Q7. The quiescent centre (QC) of the root is:✓ A group of slowly dividing cells just above the root cap that organises the stem-cell niche
Q8. Root epidermal cells that are incapable of forming root hairs are called:✓ Atrichoblasts
Q9. The lateral (vascular) cambium in roots and shoots is responsible for:✓ Secondary growth (increase in girth)
Q10. The root cap functions to:✓ Protect the root meristem and sense gravity as the root grows
Q11. SHORT-ROOT (SHR) protein is notable because it:✓ Moves from the stele into the adjacent layer to activate SCR and specify the endodermis
Q12. An auxin maximum at the root tip is important because it:✓ Positions and maintains the root stem-cell niche
Q13. The three zones of a growing root from tip to base are the:✓ Meristematic zone, elongation zone and maturation zone
Q14. Root hairs (which greatly increase absorptive surface) form in the:✓ Maturation zone of the root
Q15. Lateral root formation is triggered locally by:✓ An auxin signal that activates pericycle founder cells
Q16. The endodermis, with its Casparian strip, controls:✓ The selective movement of water and solutes into the stele
Q17. The columella cells of the root cap sense gravity using dense organelles called:✓ Statoliths (starch-filled amyloplasts)
Q18. The radial pattern of the root (epidermis → cortex → endodermis → stele) is set up largely by:✓ The SHR/SCR and auxin/PLT gene networks
Q19. Compared with the shoot meristem's WUS-CLV system, the root meristem is organised by:✓ The quiescent centre and WOX5, maintaining surrounding initials
Q20. Secondary growth in a woody root produces wood, which is:✓ Secondary xylem laid down by the vascular cambium