DROUGHT-INDUCED SHORT ROOTS ARABIDOPSIS-THALIANA - STRUCTURAL CHARACTERISTICS

In Arabidopsis thaliana, as in other Brassicaceae species, a progressi ve drought stress induced changes in root morphogenesis: from a thresh old plant water deficit, the new emerging roots remain short, hairless and often take a tuberized shape at their base while drought persists . The organization of these drought-induced roots was examined in ligh t microscopy in Arabidopsis thaliana, Columbia wild-type ecotype, and compared to the normal, well-watered lateral roots. The main structura l traits were the absence of elongation zone, the arrest of cell cap e xpansion, the lack of root hairs (despite epidermal differentiation in trichoblasts and atrichoblasts) and the radial enlargement of epiderm al and cortical cells. The early differentiation, close to the short r oot apex, of large and highly lignified metaxylem elements, the absenc e of starch accumulation in hypertrophied cortical cells appeared to b e characteristic of the species Arabidopsis, as compared to other Bras sicaceae. These structural alterations are discussed in terms of droug ht-induced changes in gene expression with regard to similar modificat ions described in root morphogenesis and root hair-defective Arabidops is mutants.