Changes in chlorophyll, polyamines and chloroplast ultrastructure of Puccinia striiformis induced 'green islands' on detached leaves of Triticum aestivum

Biochemical and ultrastructural features of 'green islands' were investigat ed using detached wheat leaves infected with the yellow rust Puccinia strii formis. Chlorophylls appear to culminate 10 d after inoculation at which po int 'green islands' were fully developed. These changes were paralleled by an increase in spermidine and spermine content which play an important role in formation of 'green islands'. Retention of chlorophyll was demonstrated in leaf tissues of wheat plants supplied with exogenous putrescine, spermi dine and spermine. Putrescine was least and spermidine and spermine most ef fective in retarding loss of chlorophylls. Ultrastructural observation reve aled that chloroplasts were regenerated in 'green islands' where many propl astids were detected. The regeneration of chloroplasts coincided with the h igh concentration of chlorophylls and polyamines particularly spermidine an d spermine. The ultrastructural changes of chloroplasts in leaf cell contai ning infection structures were parallel to physiological changes. (C) 2000 Editions scientifiques et medicales Elsevier SAS.