Sequence of morphological and physiological events during natural ageing and senescence of a castor bean leaf: sieve tube occlusion and carbohydrate back-up precede chlorophyll degradation.

The development of castor bean (Ricinus communis L. var. sanguineus) leaves from bud break to abscission was studied to determine whether senescence of phloem precedes or follows chlorophyll degradation in the course of natural ageing of leaves.

Cloning of the cDNA for glutaredoxin, an abundant sieve-tube exudate protein from Ricinus communis L. and characterisation of the glutathione-dependent thiol-reduction system in sieve tubes.

Sieve-tube exudate protein (STEP) from Ricinus communis L. seedlings consists of a characteristic set of more than 100 different polypeptides, against which a complex antiserum was raised. This antiserum cross-reacted with dominant protein species (molecular weights 10-30 kDa) present in the sieve-tube exudate and, to a lesser extent, with proteins in tissue extracts of Ricinus and a wide range of other plant species.