Page 1 - Scialabba_alii_1999

ORIGINAL PAPER Eur. J. Histochem.
43: 147-154, 1999
© Luigi Ponzio e figlio - Editori in Pavia

Structural and histochemical changes during seed development of Brassica
macrocarpa Guss

l. A. Scialabba', C. DiLiberto', L. M. Bellani2, and S. Muccifora2
'Dipartimento di Scienze Botaniche. Università di Palermo, ltaly and ' Dipartimento di Biologia Evolutiva. Univer-
sità di Siena, ltaly

Accepted 6/4/99
Key words: Brassica macrocarpa, esterases, phosphatases, proteins, phenols. seed development

SUMMARY INTRODUCTION

During seed formation of Brassica macrocmpa Brassica macrocarpa Guss. is a species endemie
the development of the embryo precedes that of the to the Egadi islands (Italy) and is an interesting
integuments; structural changes and histochemical phytogenetic resource being a wild progenitor of
changes are associated. Esterases, acid phos- severa! cultivated cabbages (Heywood and Zohary,
phatases, phenols and starch follow a sigmoid pat- 1995). lt belongs to the B. rupestris - villosa com-
tern, increasing during embryogenesis and decreas- plex (Warwick and Black, 1991 ), of which nine
ing during seed maturation. In the mature seed, threatened species are found in Sicily (Raimondo et
esterase activity is localized in the embryo and in al., l992). B. macrocarpa is present in ruderal habi-
the cells of the mucilaginous, aleuronic and hyaline tats and has populations formed by a few individu-
layers. Acid phosphatases are present in the als scattered on cliffs.
mucilaginous cells, mainly in the column, the celi Seed development is an aspect of the plant !ife
walls delimiting intercellular spaces of the cortical cycle and prepares the plant for developmental
cylinder and the adhesion areas of the cotyledons. events that occur after germination. Thus, embryo-
Phenols are scanty in the root apex, mucilaginous genesis is nota separate and isolated event in the life
cells and the palisade layer, and abundant in the cycle of a piant, but the initiation of developmental
pigmented layer. Starch is absent in ripe seeds processes that continue throughout the life of the
which have lipid and protein reserves. The major plant (Kaplan and Cooke. l997). The knowledge of
classes of storage proteins have molecular weights structural and biochemical events during seed
of 21 , 22, 27 and 30 KD and accumu late in the late development can be helpful for understanding the
stages prior to complete drying. Esterases and acid role of the biology of reproduction in the distribu-
phosphatases in mucilaginous cells of the seed tion of species belonging to the B. rupestris- villosa
integument suggest that these enzymes are complex.
involved in hydrolytic processes occurring prior to In the present study, seed development of B.
germination and that mucilages have a metabolic macrocarpa was investigated in parallel with the
function in seed-soil interactions. appearance of esterases, acid phosphatases. phe-

Correspondence to: Anna Scialabba 147
E-mail: gerrnas@unipa.it