Jinhua Zou

Effects of Cd2+ on seedling growth of garlic (Allium sativum L.) and selected physiological and biochemical characters

In this study, we determined the effects of Cd(2+) (from 10(-5) to 10(-3)M) on the growth of leaves and roots of garlic seedlings in Hoaglands nutrient solution. We also characterized the influences of Cd(2+) on a few key cellular activities, e.g., antioxidant enzymes, content of malondialdehyde (MDA), composition of photosynthetic pigments and fluorescence properties of chlorophyll on day 5, 10 and 15. The results indicated that the presence of 10(-3)M Cd(2+), but not other tested Cd(2+) concentrations, significantly decreased the development of leaves and roots of the seedlings. This level of Cd(2+) increased the activities of antioxidant enzymes and the level of MDA. With the exception of carotenoid on day 5, the presence of 10(-3)M Cd(2+) showed no significant effects on the contents of photosynthetic pigments. Intermediate concentrations of Cd(2+) caused variable effects, ranging from lowering to increasing the pigments in garlic seedlings. The presence of 10(-3)M Cd(2+), but not other tested concentrations, decreased efficiency of energy harvesting associated with photosystem II as measured by the ratio of variable to maximum chlorophyll fluorescence of intact leaves. However, Cd(2+) generated no definitive trends on photochemical quenching. Possible significance of experimental findings in relation to Cd(2+) level in garlic seedling is discussed.

Accumulation and cellular toxicity of aluminum in seedling of Pinus massoniana

BackgroundMasson pine (Pinus massoniana) is one of the most important timber species with adaptable, fast growing, versatile advantages in southern China. Despite considerable research efforts, the cellular and molecular mechanisms of A1 toxicity and resistance in P. massoniana are still poorly understood. The effects of Al on uptake and translocation of Al and other minerals, cell division and nucleolus in P. massoniana were investigated.ResultsThe results indicated that Al accumulated mainly in the roots, and small amounts were transported to aboveground organs. In the presence of Al, the contents of Mg and Fe in stems increased and decreased in roots. Accumulation of Mn in the organs was inhibited significantly. Evidence from cellular experiments showed that Al had an inhibitory effect on the root growth at all concentrations (10-5 - 10-2 M) used. Chromosome fragments, chromosome bridges, C-mitosis and chromosome stickiness were induced during mitosis in the root tip cells. Al induced the formation of abnormal microtubule (MT) arrays, consisting of discontinuous wavy MTs or short MT fragments at the cell periphery. MT organization and function of the mitotic spindle and phragmoplast were severely disturbed. The nucleolus did not disaggregate normally and still remained its characteristic structure during metaphase. Nucleolar particles containing argyrophilic proteins were accumulated and leached out from the nucleus to the cytoplasm. Evidence confirmed that these proteins contained nucleophosmin (B23), nucleolin (C23) and fibrillarin. Western immunoblot analysis revealed that the contents of three nucleolar proteins increased significantly.ConclusionBased on the information provided in this article, it is concluded that root tips of plants are the most sensitive organ to environmental stresses and the accumulation of Al ions primarily is in roots of P. massoniana, and small amounts of Al are transported to aboveground. Root apical meristems play a key role in the immediate reaction to stress factors by activating signal cascades to the other plant organs. Al induces a series of the cellular toxic changes concerning with cell division and nucleolus. The data presented above can be also used as valuable and early markers in cellular changes induced by metals for the evaluation of metal contamination.

Determination of Pb genotoxic effects in Allium cepa root cells by fluorescent probe, microtubular immunofluorescence and comet assay

AimsIn order to further understand the toxic effects of Pb on root tip cells of Allium cepa var. agrogarum, root growth, Pb uptake, cell division, DNA damage and MT cytoskeleton were investigated.MethodsFluorescence labeling; Carbol Fuchsin-staining; indirect immunofluorescent microscopy; comet assay.ResultsPb ions entered A. cepa root meristem cells within hours of exposure. The mitotic index (MI) decreased progressively with increasing of Pb concentration. Chromosomal segregation and motility are inhibited, which is directly correlated with the disorganization of the corresponding MT arrays. Pb may interact with tubulin and hinder the polymerization process, resulting in defective mitotic spindles. Pb induced DNA damage in A. cepa root nuclei.ConclusionRoot tips of plants are the most sensitive organ to environmental stresses. Root apical meristems play a key role in the immediate reaction to stress factors by activating signal cascades to the other plant organs. The data presented above can be used as valuable and early markers in cellular changes induced by metals for the evaluation of metal contamination and can be used as early warning signals for general or particular stress.

Effects of Lead on the Morphology and Structure of the Nucleolus in the Root Tip Meristematic Cells of Allium cepa L.

To study the toxic mechanisms of lead (Pb) in plants, the effects of Pb on the morphology and structure of the nucleolus in root tip meristematic cells of Allium cepa var. agrogarum L. were investigated. Fluorescence labeling, silver-stained indirect immunofluorescent microscopy and western blotting were used. Fluorescence labeling showed that Pb ions were localized in the meristematic cells and the uptake and accumulation of Pb increased with treatment time. At low concentrations of Pb (1–10 μM) there were persistent nucleoli in some cells during mitosis, and at high concentration (100 μM) many of the nucleolar organizing regions were localized on sticky chromosomes in metaphase and anaphase cells. Pb induced the release of particles containing argyrophilic proteins to be released from the nucleus into the cytoplasm. These proteins contained nucleophosmin and nucleolin. Pb also caused the extrusion of fibrillarin from the nucleus into the cytoplasm. Western blotting demonstrated the increased expression of these three major nucleolar proteins under Pb stress.

Cadmium’s Effect on the Organization of Microtubular Cytoskeleton in Root Tips Cells of Salix matsudana Koidz

The toxic effects of Cd on microtubule (MT) organization in root tip cells of S. matsudana were investigated in the present study using tubulin immunolabeling and fluorescence microscopy. Cell damage and expression level of the SmTUA1 gene in the root tips were also examined by means of propidium iodide (PI) staining and quantitative real-time PCR (qRT-PCR) technology. The MT arrays were very sensitive to Cd. At interphase, under 50 μmol/L Cd treatment for 48 h, some cortical MTs were discontinuous, inducing numbers of differently sized fragments. With increased Cd concentrations and duration of treatment, peripheral MTs appeared to be broken gradually, and the degree of disorder was enhanced. Spindle fibers even formed condensed MT at 10 μmol/L Cd for 48 h. During anaphase/telophase, there was a small part of MT absent, MT fibers were stuck to each other (even forming lumps) and could not form phragmoplast at 50 μmol/L Cd for 48 h. The cell damage of S. matsudana root tips increased with enhanced Cd concentrations and prolonged treatment time. Expression level of SmTUA1 analyzed by qRT-PCR further validated the results by indirect immunofluorescence staining. The data obtained here will be very useful to understand the mechanisms of Cd-induced cell toxicity.

Characterisation of early responses to cadmium in roots of Salix matsudana Koidz

ABSTRACT This study deals with the characterisation of early responses of roots of Salix matsudana in respect to oxidative stress, subcellular distribution, and chemical forms when exposed to 50 μmol/L Cd. Within 12 h, the root length is reduced and the contents of O2•−, H2O2, and malondialdehyde are increased by 49%, 43%, and 35%. Cd is mainly retained in the cell walls; small amounts are distributed into other cell organelles. The largest proportion of Cd is found in the NaCl extractable, pectate-, and protein-integrated fraction.

Response to NaCl Stress in Salix matsudana Koidz Seedlings

The effects of different NaCl concentrations (0.1, 0.2, and 0.4%) on plant growth, the enzymatic antioxidant system, lipid peroxidation, and cell damage were investigated in Salix matsudana Koidz to better understand the tolerant mechanism under NaCl stress. The results indicate that cell damage was induced in roots by NaCl stress as early as after just 1 h of exposure, which increased with increasing NaCl concentration and prolonged treatment. The activities of SOD, POD, and CAT in S. matsudana under NaCl stress were enhanced except for the SOD activity in leaves under 0.4% NaCl at day 28, and CAT activities in leaves exposed to 0.4% NaCl on days 21 and 28. NaCl exposure caused increasing O2 − and H2O2 contents. The MDA content in roots exposed to 0.2 and 0.4% NaCl increased except for that in 0.2% NaCl on day 14 compared with control. The MDA level in leaves of control was lower than that of all NaCl treatments. The soluble protein contents in roots increased significantly (P<0.05), except for that 0.1% NaCl during days 21 to 28. It increased significantly in leaves exposed to 0.4% NaCl, but decreased