Investigation on the effect of benzyladenine on the germination, radicle growth and meristematic cells of Nigella sativa L. and Allium cepa L.

The effect of different benzyladenine (BA) treatments which is a phyto-regulator or plant hormone on the cytology and growth of Nigella sativa L. (Black seed) and Allium cepa L. (onion) were investigated. Six concentrations of benzyladenine ranging from 5 to 55 ppm were applied for 6, 12, 18, 24, 36 and 48 h. The treatments elevate the germination percentages of Nigella sativa L. and Allium cepa L. and increase the root growth of both plants. In contrast concentrations higher than 60 ppm for 48 h were caused an inhibition effect for both plant. The root growth initiation was concentration and/or time dependent. The applied concentrations of BA showed a promotor effect on cell division in root tips of both plants and caused an increase in their mitotic index values (MI). The elevation in MI values in root tips of Nigella sativa L. was more evident than that of Allium cepa L. All treatments changed the frequency of mitotic phases as compared with the control values. All the applied concentrations of BA significantly induced a number of chromosomal aberrations in root tip cells of Nigella sativa L. and Allium cepa L. The total percentages of abnormalities in Nigella sativa L. root tip cells were more than that in Allium cepa L. with all concentrations of BA. The most dominant types of observed abnormalities were stickiness, bridges, and C-mitosis. BA treatments produced a number of mitotic abnormalities in dividing cells in root tips of both plants resulting from its action on the spindle apparatus such as C-mitosis, lagging chromosomes and multipolar at ana-telophases. Also, BA induced vacuolated nuclei and irregular prophases. The induction of chromosomal stickiness and chromosomal aberrations such as bridges indicates its action on the chromosome. Also, the induced chromosomal bridges at ana-telophases indicates true clastogenic potential of this chemical. It may be concluded that BA causes toxic effect on root tip cells of Nigella sativa L. and Allium cepa L. and this toxicity induces different types of genic and chromosomal variations

Comparative anatomical studies on some species of the genus Amaranthus (Family: Amaranthaceae) for the development of an identification guide

A study of anatomical features of mature leaves and stems (at fruiting stage) of 12 Amaranthus taxa (Family: Amaranthaceae) shows high variation between them and supplied new characters. The internal structures were evaluated to clarify their effectiveness in solving taxonomic complexity and identification difficulty in this genus. Observation of the transections of blades showed that the epidermis is uniseriate, ground tissue consists of angular collenchyma and thin parenchyma. The vascular bundles shape has three patterns crescent, ring, ovate. Also they may be united or separated while the midrib shape in cross section has two patterns in which U-shaped, cordate or crescent bundle occurs. All leaves are petiolate. The examination of the petioles exhibits new and varied characters such as petiole shape (cross section), vascular bundles (shape, number, arrangement). While the resulted characters from the observation of the stem structure showed less variation. Nineteen qualitative characters with 38 character states resulted from leaf anatomy. Only (8) characters were sufficient to generate an identification anatomical key. DELTA program was used in key-generation. Also different measurements were carried out by a photo analysis program (Image J), such as lamina thickness, mesophyll thickness, area of upper and lower epidermal cells and thickness of upper and lower epidermal cells to exhibit most possible dissimilarities between the studied species

Differential Salt Tolerance Strategies in Three Halophytes from the Same Ecological Habitat: Augmentation of Antioxidant Enzymes and Compounds

Understanding the salt tolerance mechanism in obligate halophytes provides valuable information for conservation and re-habitation of saline areas. Here, we investigated the responses of three obligate halophytes namely Arthrocnemum macrostachyum, Sarcocornia fruticosa and Salicornia europaea to salt stress (0, 100, 200, 400 and 600 mM NaCl) during their vegetative growth with regard to biomass, ions contents (Na+, K+ and Ca2+), chlorophyll contents, carotenoids, phenolic compounds, flavonoids, and superoxide dismutase, peroxidase and esterase activities. S. europaea showed the lowest biomass, root K+ content, Chl a/b ratio, and carotenoids under salinity. This reduction of biomass is concomitant with the increase in proline contents and peroxidase activity. On the other hand, the promotion of growth under low salinity and maintenance under high salinity (200 and 400 Mm NaCl) in A. Macrostachyum and S. fruticosa are accompanied by an increase in Chl a/b ratio, carotenoids, phenolics contents, and esterase activity. Proline content was decreased under high salinity (400 and 600 mM NaCl) in both species compared to S. europaea, while peroxidase showed the lowest activity in both plants under all salt levels except under 600 mM NaCl in Arthrocnemum macrostachyum compared to S. europaea. These results suggest two differential strategies; (1) the salt tolerance is due to activation of antioxidant enzymes and biosynthesis of proline in S. europaea, (2) the salt tolerance in A. macrostachyum, S. fruticosa are due to rearrangement of chlorophyll ratio and biosynthesis of antioxidant compounds (carotenoids, phenolics and flavonoids) which their cost seem to need less energy than activation of antioxidant enzymes. The differential behavior in halophytes of the same habitat confirms that the tolerance mechanism in halophytes is species-specific which provides new insight about the restoration strategy of saline areas