Anatomical studies on the adventitious roots of the geophyte
Urginea maritima (L.) Baker |
SHARAF AL-TARDEH,
THOMAS SAWIDIS, BARBARA-EVELIN DIANNELIDIS and STYLIANOS
DELIVOPOULOS*
Department of Botany, School of Biology, Aristotle
University, Thessaloniki 541 24, Greece |
Abstract
The anatomy and histochemistry of the adventitious roots of Urginea
maritima (L.) Baker and the plant's adaptive strategies to the
Mediterranean climate were investigated. The adventitious roots of U.
maritima are bounded by a multiple-layered velamen, responsible for
rapid water uptake. Both the epidermis and endodermis of the root are
uniseriate. The cortex is 741.3 µm thick and is composed of numerous
large parenchyma cells with storing character. In the cortex, scattered
idioblastic cells containing numerous raphides of calcium oxalate exist.
The average length of the calcium oxalate needles is 72±22 ìm. The
presence in the cortex of cells containing in their vacuoles soluble
polysaccharides is conspicuous after employing the Schiff's staining
technique. Also, numerous cortical cells are filled with lipids and
become intensely stained brown to black when treated with sudan black B.
Morphometric studies have shown that idioblastic cells occupy 19.83% of
the cortex relative volume, cells containing lipids 14.38%, and cells
containing polysaccharides 11.27%. The cortex storage cells occupy
34.11% of the total root volume. The average volume of the cortical
cells is 73143 ìm3. The vascular cylinder is usually 10-arched. The root
xylem consists of vessels in short radial rows. The phloem consists of
sieve elements located between the vessel rays. Urginea maritima
possessing adventitious roots proves to be efficient in storing water
during the long summer drought, less susceptible to climatic stress and
well synchronized with the climatic fluctuations. Specialized features
of U. maritima adventitious roots are, at least in part,
responsible for the species' occurrence and frequent dominance in a wide
array of semiarid ecosystems of the Mediterranean region.
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