Light‐controlled growth of the maize seedling mesocotyl: Mechanical cell‐wall changes in the elongation zone and related changes in lignification

Abstract

Cell extension in the mesocotyl elongation zone (MEZ) of maize (Zea mays L.) seedlings is inhibited by light. The growth inhibition by blue light in the MEZ was reversible upon transfer to darkness. This experimental system was used for investigating the modification of mechanical cell‐wall properties and the role of cell‐wall lignification in cell elongation. The occurrence of lignin in the cortex and vascular bundle tissues of the MEZ was demonstrated by the isolation of diagnostic monomers released after thioacidolysis of the cell walls. Concomitantly with the inhibition of growth, blue light induces an increase in cell‐wall stiffness (tensile modulus) as well as an increase in extractable lignin in the outer MEZ tissues (cortex+epidermis). Both effects are reversed when growth is resumed in the MEZ in darkness after a period of growth inhibition induced by 3 h light. In the vascular bundle light produces no comparable change in lignin content. Appearance and disappearance of phenylpropanoid material in MEZ cell walls in the light, or in darkness following a brief light treatment, respectively, can be visualized under the fluorescence microscope by characteristic changes in autofluorescence of tissue sections upon excitation with UV radiation. It is concluded from these results that light‐induced lignification of primary walls is involved in cell‐wall stiffening and thus inhibition of elongation growth in the MEZ of maize seedlings. Resumption of growth upon redarkening may be initiated by wall loosening in the uppermost MEZ region which displaces the lignified cell walls towards the lower mesocotyl region.

Aluminum tolerance and aluminum-induced deposition of callose and lignin in the root tips of Melaleuca and Eucalyptus species

“…Callose and lignin deposition in the cell wall could reduce cell-wall extensibility, a factor that regulates cell elongation (Matsumoto 2000;Schopfer et al 2001). Thus, both Al-induced callose and lignin deposition are possible causes of the inhibition of root elongation by Al treatment.…”

Early changes in root characteristics of maize (Zea mays) following seed inoculation with the PGPR Azospirillum lipoferum CRT1

“…For instance, the brittleness of barley (Hordeum vulgare L.) mutants is caused by smaller number of cellulose molecules in the cell wall (Kokubo et al 1991) and tobacco with modiWed lignin biosynthesis pathways has much diVerent mechanical behaviour than wildtypes (Hepworth and Vincent 1998). Schopfer et al (2001) demonstrated that lignin of juvenile nonwoody tissues represents a highly variable polymer whose amount and chemical composition are under developmental control. They found a sharp increase in lignin in the cortex and epidermis of young (4-day-old) maize epicotyle, which showed a close correlation to the time course of cell-wall stiVening.…”

Relationship of growth cessation with the formation of diferulate cross-links and p -coumaroylated lignins in tall fescue leaf blades

“…Lignification of primary walls has also been associated with reduced extensibility and growth of coleoptiles (Musel et al 1997;Schopfer et al 2001). Lignins in grasses are acylated with p-coumarate, which is attached primarily to syringyl units (Ralph et al 1994a;Grabber et al 1996;Lu and Ralph 1999).…”