TITLE:
Ergastic Substances (Calcium Oxalate Crystals) in the Leaf of Combretum Loefl. (Combretaceae) Species in Nigeria
AUTHORS:
Chimezie Ekeke, Ikechukwu O. Agbagwa
KEYWORDS:
Combretum, Calcium Oxalate Crystals, Crystal Sand, Druses, Mesophyll
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.5 No.15,
July
10,
2014
ABSTRACT: Leaves of twenty-two
(22) species of Combretum in Nigeria
were examined for occurrence and distribution of different types and sizes of
ergastic substances (calcium oxalate crystals). Fresh and herbarium specimens
were used for the study. These specimens were wax embedded, sectioned, mounted
and micro-photographed using Leica WILD MPS 52 microscope camera on Leitz
Diaplan microscope. Results revealed two types of calcium oxalate crystals—crystal
sand and druses. Based on the observed differences in the size of the crystals,
three groups of calcium oxalate crystals are reported [large crystals: 180.0 -
360.0 μm (241 ± 44.57 μm), moderate crystals: 90.0 - 144.0 μm (117.0 ± 20.60
μm), and small crystals: 18.0 - 72.0 μm (50.21 ± 20.42 μm)]. Crystal sand was
found only in Combretum sp. 1 but
druses of varying sizes predominated amongst species of the genus. Crystals
were distributed within the spongy mesophyll, palisade mesophyll, sub-epidermis
adaxial, sub-epidermis abaxial and between the palisade and spongy mesophyll.
The findings of this work provide information on the occurrence and
distribution of the crystals in the leaf epidermis of these taxa in Nigeria.
The formation, occurrence and distribution of the crystal type in the Combretum species constitute dependable
taxonomic character especially when combined with other characters.