Chapter 5
Roots
© 2012 by John Wiley & Sons, Ltd.
Functional Biology of Plants
Martin J. Hodson and John A. Bryant
© 2012 by John Wiley & Sons, Ltd.
Figure 5.1 (a) The Sarah Racine Root Research Laboratory at the Botanical
Gardens of Tel-Aviv University, Israel. Date palm (Phoenix dactylifera). A shoot in the
upper half of the laboratory. (b) Fibrous roots in the lower half of the laboratory.
Photos: Prof. Yoav Waisel.
Functional Biology of Plants
Martin J. Hodson and John A. Bryant
© 2012 by John Wiley & Sons, Ltd.
Figure 5.2 Taproot of parsnip (Pastinaca sativa) adapted as a storage organ.
Photo: MJH.
Functional Biology of Plants
Martin J. Hodson and John A. Bryant
© 2012 by John Wiley & Sons, Ltd.
Figure 5.3 Cross section of a primary root. From Weier et al., 1974. (Reprinted with
permission of John Wiley & Sons, Inc.)
Functional Biology of Plants
Martin J. Hodson and John A. Bryant
© 2012 by John Wiley & Sons, Ltd.
Figure 5.4 Meadow buttercup (Ranunculus acris). Cross section of triarch root, light
micrograph. Key: Cortex (Co), Passage cell (P), Endodermis (En), Pericycle (Pe),
Phloem (Ph), Protoxylem (Px), Metaxylem (Mx). Photo: Prof. Thomas Rost.
Functional Biology of Plants
Martin J. Hodson and John A. Bryant
© 2012 by John Wiley & Sons, Ltd.
Figure 5.5 Primary growth of a root illustrating the four main parts, going from the
apex backwards: root cap; zone of cell division; zone of cell elongation; and zone of
cell differentiation. From Campbell, Neil A., BIOLOGY, 2nd Edition © 1990.
Reprinted by permission of Pearson Education, Inc., Upper Saddle River, NJ.
Functional Biology of Plants
Martin J. Hodson and John A. Bryant
© 2012 by John Wiley & Sons, Ltd.
Figure 5.6 Arabidopsis thaliana. Longitudinal section of root tip, light micrograph.
Key: Root apical meristem (RAM), Root cap (RC), Epidermis (EP). Photo: Prof.
Thomas Rost.
Functional Biology of Plants
Martin J. Hodson and John A. Bryant
© 2012 by John Wiley & Sons, Ltd.
Figure 5.7 Cross section of a willow (Salix sp.) root, showing a lateral root
emerging. Key: Epidermis (Ep), Hypodermis (Hy), Cortex (Co), Lateral Root (LR),
Vascular Bundle (VB). Photo: Prof. Thomas Rost.
Functional Biology of Plants
Martin J. Hodson and John A. Bryant
© 2012 by John Wiley & Sons, Ltd.
Figure 5.8 Primary and secondary active transport across membranes. This
diagram shows the primary active transport of protons across the membrane. ATP
energy is used and the transport generates a membrane potential, ΔE. The proton
gradient is used to drive other transport systems. Here uptake is through a uniporter
(K+) or a symporter (sucrose), and efflux is through an antiporter (Na+). From
Flowers & Yeo, 1992. (Reprinted with kind permission from Springer
Science+Business Media B.V.)
Functional Biology of Plants
Martin J. Hodson and John A. Bryant
© 2012 by John Wiley & Sons, Ltd.
Figure 5.9 Pathway of mineral transport in roots. This diagram shows that there are
two paths for mineral transport in roots: symplastic, through the cell protoplasts; and
apoplastic, through the cell walls and intercellular spaces. The apoplastic pathway is
blocked at the Casparian strips in the endodermis, and at this point ions must cross
the plasmalemma if they are to continue into the stele. From Campbell, Neil A.,
BIOLOGY, 2nd Edition © 1990. Reprinted by permission of Pearson Education, Inc.,
Upper Saddle River, NJ.
Functional Biology of Plants
Martin J. Hodson and John A. Bryant
© 2012 by John Wiley & Sons, Ltd.
Figure 5.10 Casparian bands (arrows) in Glyceria maxima exodermis stained with
berberine-toluidine blue in basal parts of a root. Key: Epi, epidermis. Micrograph
from Soukup et al., 2007. (Reprinted with the permission of Blackwell Publishing)
Functional Biology of Plants
Martin J. Hodson and John A. Bryant
© 2012 by John Wiley & Sons, Ltd.
Figure 5.11 A typical root infected with an ectomycorrhizal fungus (a). In some
cases the sheath encircles the root without penetrating the root cortex (b), while in
other associations, the cortex is penetrated up to the endodermis (c). From Scott,
2008. (With kind permission from John Wiley & Sons Ltd.)
Functional Biology of Plants
Martin J. Hodson and John A. Bryant
© 2012 by John Wiley & Sons, Ltd.
Figure 5.12 Longitudinal section of a mature Medicago truncatula root nodule.
Regions of the nodule visible using confocal microscopy: 1, nodule meristem;
2, prefixation zone; 3, interzone; 4, nitrogen-fixation zone. *, Stele of root.
Micrograph from Haynes et al., 2004. (Reprinted with the permission of Blackwell
Publishing)
Functional Biology of Plants
Martin J. Hodson and John A. Bryant
© 2012 by John Wiley & Sons, Ltd.
Figure 5.13 The nitrogenase reaction in bacteroids, where electron flow is from left
to right. The main electron donor is ferredoxin, which is reduced via respiration.
Functional Biology of Plants
Martin J. Hodson and John A. Bryant
© 2012 by John Wiley & Sons, Ltd.