Biology Reference
In-Depth Information
as well as the influence of genetically selected grasses for lignin traits on
development and lignification.
II. SPATIO-TEMPORAL DEPOSITION OF
LIGNINS IN GRASSES
A major event in the development of land plants is the lignification of cell
walls. This process serves several functions including the regulation of water
flow and the establishment of tissue hydrophobicity, protection against pests
and pathogens and also contributes to tissue and plant mechanical strength
and rigidity (
Campbell and Sederoff, 1996; Kenrick and Crane, 1997
). As
these properties are necessary for the longevity and health of vascular plants,
it is not surprising that many tissues undergo, to some degree, lignification
(
Fig. 1
). Although the events of lignin deposition, both temporally and
spatially, can vary between species of plants and individual cell populations
(
Campbell and Sederoff, 1996; Whetten and Sederoff, 1995
), commonalities
are found suggesting that several underlying mechanisms of cell wall lignifi-
cation are conserved.
For nearly a century, the role of lignin in plant development has been
studied, primarily in non-grass samples and most often in woody species
(softwoods or hardwoods) due to their economic importance as raw materi-
als for chemical pulping. Over the past two decades, more attention has been
given to understand the process of lignin biosynthesis in grass species,
particularly in maize. The recent interest in the lignification of grass cell
A
B
aSc
iSc
mXy
Ep
pXy
cSc
Sc
mXy
lPa
sSc
pXy
En
Fig. 1. Lignified tissues in roots and internodes of Brachypodium distachyon.
Thirty micrometre cross-sections of root (A) and internode (B) were stained with
phloroglucinol-HCl. Only lignified tissues are labelled: mXy, metaxylem; pXy,
secondary metaxylem; En, endodermis; Ep, epidermis; Sc, sclerenchyma; aSc, scleren-
chyma adjacent to vascular bundle; sSc, sheath sclerenchyma; cSc, pseudo-cambial
sclerenchyma between xylem and phloem; iSc, interfascicular sclerenchyma; lPa,
lignified parenchyma.
