The Physiology of Flowering Plants - KHAM PHA MOI

Division frequencyElongation rate240 VEGETATIVE DEVELOPMENTABRoot hairEpidermisSteleCortexPericycleProcambiumRoot apical meristemQuiescentcentreEpidermisLateralroot capCap columellaC****EndodermisDCortexPericycle****Fig: 9:16 Root structure. (A) Exterior view of a developing root of Arabidopsis thaliana. Scale bar = 100 mm. (B) Generalized diagramshowing the typical structure of a developing root, indicating zones of cell division, expansion and differentiation. Ticks on the axis areat 1 mm intervals for maize (Zea mays) and 50 mm intervals for Arabidopsis. (C) Transverse section through an Arabidopsis root taken1 mm behind the tip. Cells have been shaded for clarity. The protoxylem and protophloem are shaded dark grey and lie at 908 to eachother. Epidermal cells overlying two adjacent cortical cells (indicated by *) have the potential to develop into a root hair. Scale bar = 25mm. (D) Longitudinal section through an Arabidopsis root tip. The columella and lateral root cap are shown in grey. The cells at thequiescent centre are hatched. The black arrow shows a cortex initial and its daughter cell. The white arrow shows the nextdevelopmental step, in which a lateral division has given rise to the cortex and endodermis. (A) from Dr Liam Dolan and (C) fromDolan et al. (1993). # Company of Biologists Ltd. (B) redrawn from Jacobs (1997). (D) redrawn from van den Berg et al. (1997).# Nature Publishing Group.