S. Karataglis

Responses of maize (Zea mays L.) plants to copper stress—I. Growth, mineral content and ultrastructure of roots

Changes in the morphology, physiology and ultrastructure of root systems of Zea mays cv. Aris under various Cu treatments were investigated. A progressive decrease of root length and biomass with increasing Cu in nutrient solution was observed. Mineral content and distribution were markedly affected by Cu. The roots accumulated significantly higher amounts of Cu than the above ground parts. Significant reduction of root calcium and iron contents as well as extensive damage to root epidermal cells occurred at the higher Cu concentration. In the remainder of the root, the effects of Cu (80 μM) varied within the same tissues. Thus, there were cortical or stelar cells with disintegrated cytoplasm, next to cells with well preserved plasmalemma, tonoplast and cytoplasm including cell organelles. Multi-lamellar bodies inside the vacuoles indicated an increased activity in digestion of the cytoplasmic components under Cu stress. Deposits of a less dense and less compact material were found behind the plasmalemma associated with the cell wall as well as an accumulation of dense material attached to the cell walls; cells with such deposits in their walls revealed extensive cytoplasmic damage. However, root ultrastructure was affected less than the morphology and physiology. The occurrence of well preserved cells indicates that Zea mays root cells do not respond uniformly to stressful conditions and suggests the development of a resistance strategy of maize roots to Cu-toxicity.

Field study of the effects of excess copper on wheat photosynthesis and productivity

Abstract Copper concentration in wheat plants growing in a Cu-contaminated area, was 3.5-times higher than that of the control, while the total chlorophyll (a + b) content of plants growing in an ore site was significantly reduced. The significant decline of the chlorophyll concentration in the Cu-stressed wheat plants in relation to the decrease in the chlorophyll a/b ratio was an indication of the poor condition of those plants and the lack of adaptive adjustment in pigment concentrations to high Cu levels. Plants grown in ore soils displayed a significantly smaller height and length of ear and produced significantly fewer seeds and spikelets per ear, while grain filling and development were negatively affected. The relative decrease in the assimilation rate for stressed plants was 90%. Increased Cu levels in the soil led to a decrease of the stomatal conductance (43%) and of the transpiration rate (10%). The water use efficiency (i.e. the ratio between leaf photosynthesis and transpiration) of the stre...

Comparative Responses of a Copper-tolerant and a Copper-sensitive Population of Minuartia hirsuta to Copper Toxicity

Summary The response of two populations of Minuartia hirsuta with different copper tolerance to an excess of copper was studied. The population originatin from copper contaminated sites showed a distinct tolerance to copper. A more vigorous growth of copper tolerant plants under increasing copper concentrations was found, since their root-length growth and chlorophyll content were higher than the control, as well as their unchanged percentage survival. In contrast, copper treatments caused progressive reduction in the above mentioned parameters in copper-sensitive plants. The total uptake of copper and its distribution between roots and shoots differ significantly between the two populations. At all external copper concentrations the sensitive plants took up more copper, and a higher percentage of the total copper concentration was allocated to the shoot, compared with the tolerant plants. A distinct population differentiation was observed with respect to the distribution of calcium, magnesium, iron and potassium in roots and shoot-leaves. Under copper treatments the sensitive population showed a direct relation to the calcium concentration both in roots and shoot-leaves, while the tolerant population revealed an inverse relation to calcium concentration in plant tissues. The magnesium concentration decreased in the presence of increasing copper levels both in tolerant and, especially, sensitive populations. The total iron concentration seems to be unaffected under an excess of copper in tolerant plants, while an inverse relation of iron concentration to external copper supply in the sensitive population was observed. The concentration of potassium dropped more in sensitive plants. It seems likely that a constitutive copper tolerance mechanism also operates both in shoot and root and that this also contributes to the increased copper requirements of tolerant plants.

Photoacoustic measurements of photosynthetic activities in intact leaves under copper stress

Abstract Photoacoustic spectroscopy was used to monitor Cu damage to photosynthesis by measuring photochemical energy storage (PES) at high frequency of 600 Hz and yield of O 2 evolution (Aox/Apt) at low frequency of 19 Hz in intact leaves of a Cu-tolerant ( Silene compacta ) and a non-Cu-tolerant ( Alyssum montanum ) species. The results indicated that Cu affected root growth (RRG), more severely than photoacoustic parameters in both species. Plants of S. compacta grown in lower Cu concentration revealed an enhancement phenomenon on RRG, PES and Aox/Apt, in contrast, plants of A. montanum revealed a slight decrease in the above mentioned parameters. A remarkable decline of PES and Aox/Apt for both species, was observed, at higher Cu concentrations, a fact considered to reflect inhibition of the photsynthetic e − flow in thylakoids. PES was less affected by Cu stress than O 2 evolution showing a differential sensitivity of two photosystems in Cu. Photosystem II (PSII) seemed to be more sensitive because of degradation and leakage of chloroplasts membranes, inducing a decline in yield of O 2 evolution. On the other hand, PES was appreciable because of cyclic e − transfer around the intact or less inhibited photosystem I (PSI).

Effect of heavy metals on isoperoxidases of Wheat

The influence of increasing concentrations of copper, zinc, lead, nickel, chromium and cadmium on 14-day-old seedlings of wheat (Triticum aestivum L. cv. Vergina) was studied. Plants were grown in 1/10 strength Rorison’s nutrient solution with increasing concentrations of each of the metals added separately. The toxicity of metals depressed shoot growth but the most evident symptoms were on roots. The concentration of each metal which caused inhibition of root growth was chosen to study the influence of metals on isoperoxidases of wheat shoots. The concentrations employed did not alter the number of peroxidase bands but almost in all cases enhanced the intensities of bands of pH 4.0-4.2 and 5.0-5.4, while they decreased the intensities of bands of pH 4.2-4.6 and 5.4-6.5.The similar effects of the different heavy metals employed may suggest similarity in metal action on wheat isoperoxidases. The increased intensities of peroxidase bands may be considered as an indication of enhanced senescence caused by the heavy metal treatments.Generally, our results suggest that the heavy metals employed have caused complex changes on the multiple forms of peroxidases.

Aluminum toxicity effects on durum wheat cultivars

Abstract The effects of aluminum on biomass, nutrients and kinases were studied in two durum wheat cultivare (Triticum durum Desf. cvs Sapfo, Capeiti 82) grown in nutrient solutions (pH 4.5) at seven Al levels (0, 9.3, 18.5, 37.1, 74.1, 148, and 297 μM). The most evident Al toxicity symptom was a reduction in root growth. Sapfo showed greater Al tolerance than Capeiti 82. However, both cultivare must be characterized as Al‐sensitives. Aluminum in the nutrient solution above 74.1 μM significantly (P<0.05) reduced root growth of both durum wheat cultivare. The concentration of 74.1 μM Al can be suggested for screening of durum wheats on the basis of tolerance to Al. The concentrations of the nutrients Ca, Mg, K, and Fe in the plant tissues of both cultivare decreased even at low Al levels. The decrease of Ca+2 content in leaves and roots of the two durum wheat cultivare was almost the same while the less sensitive cultivar Sapfo retained larger amounts of Mg+2 in roots and leaves compared with the more sens...

Pollen morphology in relation to the taxonomy and phylogeny of some native Greek Aegilops species

The pollen morphology of some native Greek Aegilops species is investigated in LM (quantitative pollen characters) and SEM (exine sculpture) using acetolysed material. Furthermore, quantitative data are subjected to a multivariate analysis. The tetraploid Ae. cylindrica and its diploid parent Ae. caudata show a distinct morphological affinity as regards their quantitative pollen profile and the features of the exine sculpture. The tetraploid Ae. triuncialis is morphologically divergent from both its parents Ae. caudata and Ae. umbellulata due to the very large values of its quantitative pollen characters. However, the SEM survey of the exine sculpture indicates a rather high degree of similarity between Ae. triuncialis and Ae. umbellulata. No significant differences have been found between the two varieties of Ae. caudata (caudata and polyathera) concerning the quantitative pollen characters as a total or the morphology of the exine sculpture. The resultant clustering of the taxa on the basis of the quantitative pollen characters as well as the recorded similarities of their exine pattern are related to their sectional classification based on cytogenetical and morphological data.

Biosystematic Study of the Genus Taeniatherum in Greece

Summary Two diploid taxa of the genus Taeniatherum, T. caput-medusae I and T. caput-medusae II, sometimes in coexistence, were collected in 16 localities in Greece and studied by combining karyotype analysis and seed protein profiles obtained by isoelectric focusing. The findings of the karyotype analysis suggest that the two taxa must be considered to be conspecific. The protein profile data are in agreement with this conclusion implying also that the two taxa might be in an effective phase of evolutionary change which will probably result in the formation of two different species.

Pollen Morphology and its Contribution to the Taxonomy of Some Native Greek aegilops Species.

Pollen morphological characters (mainly those of the exine sculpture) have been used as a means in studying the phylogeny and taxonomy of certain genera of the Gramineae family(Grant 1972, Rajendra et al. 1978, Sun and Liang 1991). In the present study some native Greek Aegilops species of the wider group of genomes C,U which comprises the diploids Ae. umbeUulata U and Ae. caudata var. typica and polyathera C. and tetraploid hybrids Ae. triuncial is UC and Ae. cylindrica DC (genome symbols after Kimber and Tsunewaki 1988) are investigated for their pollen quantitative characters. The results are compared to those of different taxonomical discriminations based on morphological (Zhukovsky 1928. Eig 1929) and cytogenetical data (Kihara 1954. Chennaveeraiah 1960).