Leaf Blade Area Research Articles

Adaptation of the C4 grass Panicum maximum to defoliation is related to plasticity of N uptake, mobilisation and allocation patterns

Dry mass production and persistence of Panicum maximum pastures depends on nitrogen supply. Defoliation influences N uptake and allocation patterns yet its effects on plasticity of N dynamics in P. maximum have not been investigated. Stable isotopes of N (15N) were used in order to test the hypothesis that defoliation in terms of proportion of the leaf area removed effects N mobilisation, uptake and allocation patterns in P. maximum. The plants were initially cut weekly to a height of either 0.15 m or 0.30 m for seven weeks. Eight weeks after the first defoliation, all plants were defoliated for a final time to remove 0, 25, 50, 75 or 100 % of the area of each individual leaf blade of the main tiller. Root N uptake was reduced when all leaf area was removed, but more lenient defoliation improved N uptake due to a positive effect on specific N uptake. Young leaves, side tillers and roots were the main sinks for N from root uptake. Roots of P. maximum became a net source of N for mobilisation immediately after severe defoliation. Root uptake was the main source of N for new growth in P. maximum plants. Allocation pattern of mobilised N was different from that of N derived from root uptake. It was concluded that adaptation of P. maximum to defoliation is related to plasticity of N uptake, mobilisation and allocation, but changes in N dynamics did not offset negative impacts of complete defoliation of the plants.

Size-dependent variability of leaf and shoot hydraulic conductance in silver birch

Variation in leaf and shoot hydraulic conductance was examined on detached shoots of silver birch (Betula pendula Roth), cut from the lower third (shade leaves) and upper third of the crown (sun leaves) of large trees growing in a natural temperate forest stand. Hydraulic conductances of whole shoots (K S), leaf blades (K lb), petioles (K P) and branches (i.e. leafless stem; K B) were determined by water perfusion using a high-pressure flow meter in quasi-steady state mode. The shoots were exposed to irradiance of photosynthetic photon flux density of 200–250 μmol m−2 s−1, using different light sources. K lb depended significantly (P < 0.001) on light quality, canopy position and leaf blade area (A L). K lb increased from crown base to tree top, in parallel with vertical patterns of A L. However, the analysis of data on shade and sun leaves separately revealed an opposite trend: the bigger the A L the higher K lb. Leaf anatomical study of birch saplings revealed that this trend is attributable to enhanced vascular development with increasing leaf area. Hydraulic traits (K S, K B, K lb) of sun shoots were well co-ordinated and more strongly correlated with characteristics of shoot size than those of shade shoots, reflecting their greater evaporative load and need for stricter adjustment of hydraulic capacity with shoot size. K S increased with increasing xylem cross-sectional area to leaf area ratio (Huber value; P < 0.01), suggesting a preferential investment in water-conducting tissue (sapwood) relative to transpiring tissue (leaves), and most likely contributing to the functional stability of the hydraulic system, essential for fast-growing pioneer species.

Common allometric response of open-grown leader shoots to tree height in co-occurring deciduous broadleaved trees.

Morphology of crown shoots changes with tree height. The height of forest trees is usually correlated with the light environment and this makes it difficult to separate the effects of tree size and of light conditions on the morphological plasticity of crown shoots. This paper addresses the tree-height dependence of shoot traits under full-light conditions where a tree crown is not shaded by other crowns. Focus is given to relationships between tree height and top-shoot traits, which include the shoot's leaf-blades and non-leafy mass, its total leaf-blade area and the length and basal diameter of the shoot's stem. We examine the allometric characteristics of open-grown current-year leader shoots at the tops of forest tree crowns up to 24 m high and quantify their responses to tree height in 13 co-occurring deciduous hardwood species in a cool-temperate forest in northern Japan. Dry mass allocated to leaf blades in a leader shoot increased with tree height in all 13 species. Specific leaf area decreased with tree height. Stem basal area was almost proportional to total leaf area in a leader shoot, where the proportionality constant did not depend on tree height, irrespective of species. Stem length for a given stem diameter decreased with tree height. In the 13 species observed, height-dependent changes in allometry of leader shoots were convergent. This finding suggests that there is a common functional constraint in tree-height development. Under full-light conditions, leader shoots of tall trees naturally experience more severe water stress than those of short trees. We hypothesize that the height dependence of shoot allometry detected reflects an integrated response to height-associated water stress, which contributes to successful crown expansion and height gain.

Determination of Merremia cissoids leaf area using the linear measures of the leaflets

Knowledge of the weed leaf area may give support to study the interference relationships between weeds and crops. The objective of this research was to determine a mathematical equation for M. cissoides leaf area estimation based on the relationship between the leaf blade linear measures. Leaves of the species were collected from a variety of agroecosystems at São Paulo State University, Jaboticabal, São Paulo State, Brazil, measuring the length (L), maximum width (W) and real leaf blade area of the three kinds of leaflets. Linear equations Y = a x (X) were estimated for each kind of leaflet. The confidence intervals of the primary leaflet equation overlapped those ones from the secondary leaflet equation, and then only one equation was considered for these leaflets. So, an equation of principal leaflet plus that one of primary + secondary leaflets were used to determine the M. cissoides leaf area. Thus, the leaf area of the species might be determined by the sum of the leaf areas of the principal leaflet with the primary + secondary leaflets, according to the equation LAest = 0.501 x (X) + 2.181 x (Z), where X indicates L x W of the principal leaflet and Z indicates medium L x W of the primary + secondary leaflets, respectively.

Development and plasticity of endangered shrubLindera melissifolia(Lauraceae) seedlings under contrasting light regimes

AbstractLindera melissifolia(Walt.) Blume seedlings were raised in a growth chamber to determine the effects of light availability on shoot growth pattern, and basic leaf and stem growth.Lindera melissifoliaseedlings exhibited a sympodial shoot growth pattern for 3 months following emergence from the soil medium, but this pattern was characterized by a reduction in leaf blade area approximately 30 days after emergence, followed by increases in leaf blade area. Seedlings receiving low light were 76% taller than seedlings receiving high light. Seedlings receiving low light also had larger leaf blade dimensions, blade area, seedling leaf area, and greater mass. Seedlings raised in high light had a greater proportional distribution of biomass in the roots, suggesting possible water stress from greater vapor pressure deficits. Furthermore, these seedlings displayed sharp angles of blade inclination and blade folding – acclimation that reduces exposure to light and subsequent higher leaf temperatures in open environments. These differences in morphological response to light resulted in high phenotypic variability inL. melissifoliaseedlings.Lindera melissifoliaseedling development showed a brief period of phenotypic plasticity, followed by ontogenetic plasticity. The short period of phenotypic plasticity may, however, have profound ecological implications for the conservation and recovery of this federally endangered shrub. Further experimentation should take into account the development of ontogenetic standards for comparisons of plant traits in addition to temporal standards.

Variações na morfoanatomia foliar de Aechmea lindenii (E. Morren) Baker var. lindenii (Bromeliaceae) sob distintas condições ambientais

Aechmea lindenii (E. Morren) Baker var. lindenii (Bromeliaceae-Bromelioideae) ocorre em restingas e Floresta Pluvial de Encosta Atlântica em Santa Catarina e Nordeste do Rio Grande do Sul, BR. Pode ser encontrada total ou parcialmente exposta à irradiação solar e em distintas formas de vida - terrícola, rupícola e epifítica. O objetivo deste trabalho foi comparar morfoanatomicamente às características de folhas de A. lindenii var. lindenii em distintas condições ambientais. Foram coletadas, na Ilha de Santa Catarina (Florianópolis, SC), folhas de plantas terrícolas em restinga herbácea (alta irradiação solar), rupícolas de costões rochosos (alta irradiação solar), terrícolas e epifíticas de sub-bosques (baixa irradiação solar) de restinga arbórea e rupícolas de sub-bosque (baixa irradiação solar) de Floresta Pluvial de Encosta Atlântica. Foram mensurados comprimento, largura, área da lâmina e bainha foliar, densidade estomática, comprimento e largura das células-guarda, espessura total e das estruturas constituintes na lâmina foliar. As características anatômicas qualitativas são semelhantes nas distintas condições analisadas. A baixa irradiação solar determina maior expansão da área foliar, decorrente do alongamento da lâmina. Lâmina e bainha foliares têm maior largura sob alta irradiação. A densidade estomática foi maior em folhas de plantas sob alta irradiação solar. A espessura total da lâmina foliar foi menor em plantas terrícolas sob alta irradiação, porém não mostrou diferenças estatísticas significativas entre as outras condições.

An investigation of differences in fruit yield and components contributing to increased fruit yield in Japanese and Dutch tomato cultivars

Tomato fruit yield per area in Japan is 88% lower than that in The Netherlands, because higher-yielding tomato cultivars are bred and cultivated in The Netherlands. In this study, we investigated differences between the Japanese common cultivar ‘Reiyou’ and the Dutch high-yielding cultivar ‘Levanzo’ in fruit yield and components contributing to an increase in fruit yield using the low-node-order pinching and high-density plant training system used in Japan. Fresh and dry fruit yield of ‘Levanzo’ were significantly higher than those of ‘Reiyou’. Estimated leaf blade area of the whole plant and solar radiation on individual leaves were higher in the ‘Levanzo’ canopy than in that of ‘Reiyou’. Although transpiration rate and stomatal conductance were similar in the two cultivars during the latter half of the fruit development period, the photosynthetic rate in ‘Levanzo’ was higher than that in ‘Reiyou’ during the fruit development period. The difference in photosynthetic rate was because chlorophyll a and b content had not decreased in ‘Levanzo’ compared with that in ‘Reiyou’ at 50 days after flowering, corresponding to the latter half of the fruit development period. Transcriptional levels of LeSUT1, which determines sucrose loading activity in source leaves, did not differ between the two cultivars. The higher tomato fruit yield of ‘Levanzo’ compared with that of ‘Reiyou’ was caused by a higher photosynthetic rate, increased solar radiation on individual leaves, and the large sink size due to numerous fruits, but not by sucrose loading activity.

Aspectos estruturais de folhas de indivíduos de &lt;I&gt;Guapira opposita&lt;/I&gt; (Vell) Reitz (Nyctaginaceae) ocorrentes em Restinga e na Floresta Ombrófila Densa&lt;p&gt;doi: 10.5007/2178-4574.2010v39p59

Guapira opposita is a tree species that occurs in the shaded and humid environment of the Floresta Ombrofila Densa and in sunny and dry sandbank areas. This work had as objective to compare the anatomical characteristics of the leaves from forest and sandbank, looking for differences that can favor the survival of the species in such different environments. The results showed that the variation of some characteristics between forest and sandbank leaves help to explain the adaptation of the species to these environments, as leaf area, stomatal density, chlorophyll contents and thickness of epidermal cells, cuticle membrane and leaf blade. The form of leaves, the guard cell dimensions and stomatal pore size, on the other hand, did not show clear behaviour related to the variation in the light intensity.

Anatomical and physiological characteristics relating to ionic relations in some salt tolerant grasses from the Salt Range, Pakistan

Populations of three salt tolerant forage grasses (Cynodon dactylon, Imperata cylindrica, and Sporobolus arabicus) were collected from the salt-affected soils of the Salt Range and normal non-saline soils of the Faisalabad region to assess their mechanism of adaptation to saline stress by determining ion relations and some specific anatomical modifications. The population of S. arabicus from the Salt Range showed increased growth (root and shoot length, and root and shoot dry weights) under saline conditions. Salt tolerance in this species was related to structural modifications such as increased area of root, stem, leaf blade, and leaf sheath for toxic ion accumulation, increased vesicular hair density in leaves and aerenchyma formation in leaf sheath for ion exclusion. Uptake of toxic ions was high in the Salt Range population of C. dactylon and salt tolerance was related to ion exclusion through specific leaf structural modifications such as vesicular hairs. Salt tolerance in the Salt Range population of I. cylindrica was mainly associated with restricted uptake of toxic Na+ and Cl− at root level, and accumulation of toxic ions via increased succulence in leaf blades and leaf sheaths in addition to some excretion of toxic ions through leaf sheath aerenchyma.

Predicting the Leaf Area ofVitis viniferaL. cvs. Cabernet Sauvignon and Shiraz

The planimetric area of grapevine leaf blades (LA) is required as input data in many grapevine growth models and quantitative studies of the soil/plant/atmosphere continuum. A subset of 300 scanned grapevine leaves was used to identify and compare allometric statistical models predicting the leaf area of grapevines (cultivars Cabernet Sauvignon and Shiraz). The mean absolute error (MAE), root mean square error (RMSE), and Δ (RMSE – MAE) were used as discriminatory criteria. Six families of models drawn from the literature were compared with stepwise regression using up to six possible predictor variables. Each family was fitted to each cultivar for three vineyard sites. Generic models were computed by aggregating the data across sites and cultivars. The Queensland (stepwise regressions) family performed best, closely followed by Elsner2 and Montero. The MAE of some generic models was at times less than that of their components because of the influence of sites and/or cultivars. Site- and cultivar-specific stepwise regressions are generally the most accurate methodology for estimating leaf surface area. Simple models were generally less accurate than models integrating several predictor variables.

Sequence of Anatomical Symptom Observations in Citrus Affected with Huanglongbing Disease

This study was undertaken to develop a better understanding of the relationship between symptom development and the nature of the citrus disease, huanglongbing. The most characteristic symptom of huanglongbing (HLB) is the non-symmetrical mottled chlorosis of leaf blades. Starch accumulation and phloem collapse have been associated with symptom development in this disease presumed to be caused by Candidatus Liberibacter asiaticus. Several hypotheses regarding phloem disruption to starch accumulation to chlorosis evolved concerning symptom development. These were tested using light and Transmission Electron Microscopy (TEM). Samples collected and fixed for TEM with various stages of HLB symptoms, revealed the following: starch accumulation occurred after phloem plugging and cell collapse and therefore, localized carbohydrate deficiency may be a factor. Starch packing of chloroplasts did not rupture the outer membranes, but the inner grana structure was disrupted thus, leading to chlorosis. This occurred only in parts of the leaf where phloem plugging occurred. Sieve elements were obstructed by both amorphous and filamentous materials and both occurred in readily observed amounts, while bacteria were insufficient to directly cause plugging. The amorphous material was positively identified as callose by immunoassay with gold labeling. Phloem protein 2 was identified in the filamentous plugging material using immunoassay with gold labeling. This information supports the development of HLB symptoms in the following sequence: phloem plugging and necrosis with cell wall swelling of sieve elements and companion cells followed by some phloem cell collapse, presumed sugar backup in localized leaf blade areas leading to starch accumulation until chloroplast structure is disrupted with resulting chlorosis.

Influence of cormorant Phalacrocorax carbo colony on biometrical parameters of three-nerved sandwort Moehringia trinervia (Caryophyllaceae) leaves and seeds

Żolkoś K., Meissner W.: Influence of cormorant Phalacrocorax carbo colony on biometrical parameters of three-nerved sandwort Moehringia trinervia (Caryophyllaceae) leaves and seeds. Ekologia (Bratislava), Vol. 29, No. 1, p. 55–64, 2010. Investigation on the influence of fertilization on enlargement of leaf dimensions and seed production of Moehringia trinervia was carried out in July 2006 on Vistula spit, within the largest European breeding colony of cormorant Phalacrocorax carbo, where multiple enhancement of NPK in the soil due to deposition of guano was noted. The control sample was taken from place located ca. 500 m away from the colony, where cormorants never nested. Leaves from the area within the colony were significantly larger and more rounded than leaves of plants growing outside the colony. Enlargement of leaf blade area allows plant to develop assimilation apparatus, which in turn affects on improvement of ability to absorb and transform greater amounts of nitrogen into organic compounds. It had probably an influence on extension of seed number, because plants within the colony area produced significantly more seeds than plants outside the colony. However seeds from the colony were twice lighter seed from the control sample, which may facilitate their dispersal and occupancy on larger area. Probably in this way Moehringia trinervia adapts to the unlimited availability of nutrients coming from bird excrements.

RESPONSE OF BARLEY PLANTS TO ORGANIC MANURE AND NITROGEN FERTILIZATION UNDER SANDY SOILS CONDITION

Two field experiments were carried out at one of the farm of EL Zawiah Zone , Libya during 2006 / 2007 and 2007/2008 season to study the response of barley plants cv California mariot to cheep manure ( 0, 50, 75 and 100 m3/ hectare )and nitrogen fertilizer such as, urea (46 % N ) (100 ,150 and 200 kg N / hectare). A split-plot design with three replicates was used in both growing seasons. The results revealed that, application of organic manure at the rate of 75m3/hectare gave highest values on vegetative characters(plant height, number of tillers/m3,number of spikes/m3,spike length and flag leaf blade area) and total chlorophyll, as well as yield and its components(1000-grain weight, grain yield Ardab/hectare and straw yield). By increasing the nitrogen fertilization level up to 200 kg N/hectare gave too the highest values of the characters above mentioned. Regarding the interaction effect, the treatment of 75m3 cheep manure/hectare and 200kg N/hectare, was recorded the highest values of most studied characters in this respect.

IMPROVING WATER USE EFFICIENCY AND YIELD OF MAIZE (Zea mays, L.) BY FOLIAR APPLICATION OF GLYCINEBETAINE UNDER INDUCED WATER STRESS CONDITIONS

Two field experiments were conducted in a sandy soil in the extension field in El-Kassasein, Ismailia Governorate, Egypt during 2007 and 2008 summer seasons. The work aimed to study the effect of five levels of glycinbetaine (0, 5, 10, 15, 20mM/fad) on the response of SC 10 maize hybrid to three rates of drip irrigation water (1.00. 0.80 and 0.60 of the estimated crop evapotranspiration, which represented 2625, 2100 and 1575 m3water/fad, respectively). The most important findings could be summarized as follows: Irrigation by 1575 m3/fad instead of 2625 m3/fad reduced significantly ear leaf blade area, total chlorophyll, relative water content and leaf water potential, except the content of GB in leaves which was significantly increased in both seasons. Meanwhile, increasing the level of glycinebetaine (GB) up to 15 mM/fad increased these traits and the content of GB in leaves compared with their untreated analogues. Decreasing the amount of irrigation water from 2625 to 1575 m3/fad reduced significantly the grain yield, protein yield and water use efficiency (IWUE). While, the relative increase percentages due to application of 15mM GB/fad compared with zero GB were 28.47 and 25.30%, 54.53 and 47.25%, and 27.61 and 25.10% for these traits in both seasons, respectively. The interaction between both studied factors showed that under moderate water stress condition (2100 m3/fad) without GB addition the responses of these traits were only 11.59 and 10.77 ardab/fad, 135.29 and 119.69 kg/fad and 0.773 and 0.718 kg m-3 compared with 14.31 and 13.49 ardab/fad, 195.07 and 176.25 kg/fad and 0.954 and 0.899 kg m-3 when the concentration of GB was increased to 15mM GB/fad in both seasons, respectively.

Fatores que afetam a oviposição de Bemisia tabaci (Genn.) biótipo B (Hemiptera: Aleyrodidae) em pimentão

Bemisia tabaci (Gen.) biotype B is considered a pest of economical importance for several vegetables. The oviposition behaviour of the whilefly was evaluated in sweet pepper plants. The trials were carried out under greenhouse condition and in the Laboratory of Entomology of DEFERS/UNESP, Campus of Ilha Solteira-SP, with the sweet pepper Magali-R genotype. The effect of plant age on the whitefly oviposition was evaluated in free-choice tests, in plants, 25, 30, 35, 40 and 45-day-old, as egg distribution in the plant and on the leaf blade was evaluated in 35-days-old plants. In a no-choice tests, 35-day-old plants were used to evaluate the effect of the densities of 50, 100, 150, 200 and 250 adults per plant on the number of eggs laid by insects. The silverleaf whitefly preferred to oviposit on the third to sixth leaflets, of the medium and superior part of plants of sweet pepper; the leaf blade areas, located in the lobes right and left close the base of the leaf were the preferential site for whitefly oviposition. Older plants, 40- and 45-day-old, were preferentially used for oviposition, and 200 and 250 adults per plant were both enough to lay a number of eggs that allowed to differentiate among sweet pepper genotypes with different whitefly resistance levels.

A mutation in the uvi4 gene promotes progression of endo‐reduplication and confers increased tolerance towards ultraviolet B light

We have isolated and characterized a new ultraviolet B (UV-B)-resistant mutant, uvi4 (UV-B-insensitive 4), of Arabidopsis. The fresh weight (FW) of uvi4 plants grown under supplemental UV-B light was more than twice that of the wild-type. No significant difference was found in their ability to repair the UV-B-induced cyclobutane pyrimidine dimers, or in the amount of UV-B absorptive compounds, both of which are well-known factors that contribute to UV sensitivity. Positional cloning revealed that the UVI4 gene encodes a novel basic protein of unknown function. We found that the hypocotyl cells in uvi4 undergo one extra round of endo-reduplication. The uvi4 mutation also promoted the progression of endo-reduplication during leaf development. The UVI4 gene is expressed mainly in actively dividing cells. In the leaves of P(UVI4)::GUS plants, the GUS signal disappeared in basipetal fashion as the leaf developed. The total leaf blade area was not different between uvi4 and the wild-type through leaf development, while the average cell area in the adaxial epidermis was considerably larger in uvi4, suggesting that the uvi4 leaves have fewer but larger epidermal cells. These results suggest that UVI4 is necessary for the maintenance of the mitotic state, and the loss of UVI4 function stimulated endo-reduplication. Tetraploid Arabidopsis was hyper-resistant to UV-B compared to diploid Arabidopsis, suggesting that the enhanced polyploidization is responsible for the increased UV-B tolerance of the uvi4 mutant.

The effect of etiolation and shading of stock plants on rhizogenesis in stem cuttings of Cotinus coggygria

In order to improve vegetative propagation of a difficult to root Cotinus coggygria the stock plants were subjected to: etiolation, shading and spraying with IBA, combined with the application of two commercially available rooting powders. The IBA treatment was more suitable for rooting of C. coggygria cuttings than the NAA application and it enhanced rhizogenesis regardless of the form of auxin application (foliar application to a stock plant or a rooting powder used directly on cuttings) and the amount of light provided to stock plants. Etiolation did not improve rhizogenesis in stem cuttings, however, reduction of light intensity by 50% and 96% of the ambient prior to harvest of cuttings affected rooting positively. Positive effects of shading can be ascribed to changes in shoot anatomy, i.e. a weaker sclerenchyma development. Synergistic effect of shading and foliar auxin application can result from the increase in leaf blade area and/or thinner lower epiderm. Enhanced rooting in cuttings from shoots grown out under reduced light intensity was accompanied by decrease in the contents of total soluble sugars, soluble proteins and free ABA and by increase in total chlorophyll, free amino acids, polyphenolic acids and free IAA contents.

Crescimento de espécies do gênero Brachiaria sob alagamento em casa de vegetação

Objetivou-se avaliar a tolerância ao alagameto de quatro espécies de Brachiaria (B. decumbens,B. brizantha, B. humidicola e B. mutica), a partir de suas características morfogênicas, fisiológicas e produtivas. Os tratamentos foram arranjados segundo esquema fatorial 4 x 3 quatro espécies de Brachiaria e três níveis de disponibilidade de água no solo (capacidade de campo, lâmina d'água de 1 e 10 cm acima do solo). O delineamento experimental foi de blocos completos ao acaso, com três repetições. O experimento foi instalado em casa de vegetação, utilizando-se colunas de PVC com 60 cm de altura x 30 cm de diâmetro. Os níveis de alagamento foram impostos a partir do 22º dia de rebrota após corte de uniformização. O acréscimo de água aos vasos, necessário para satisfazer a lâmina d'água a 1 e 10 cm do nível do solo nos respectivos vasos, foi controlado com o auxílio de furos presentes nas paredes dos vasos a 1 e 10 cm acima do nível do solo, respectivamente. O alagamento comprometeu a taxa de alongamento e acentuou a taxa de senescência das lâminas foliares, independentemente da espécie. Observou-se controle estomático das trocas gasosas em folhas de todas as espécies. O alagamento reduziu a fotossíntese líquida das espécies de Brachiaria, exceto de B. mutica, que superou as demais espécies sob a lâmina d'água de 10 cm acima do solo. Também diminuiu significativamente a área e o peso das lâminas foliares verdes, exceto em B. mutica, que apresentou apenas ligeira tendência de queda. A B. muticaapresentou numerosas raízes adventícias, que, possivelmente, lhe conferiram superior tolerância ao alagamento.

Accumulation of biomass and some macroelements in tomato plants grown in media with (+)-usnic acid

The results of studies on the effect of (+)-usnic acid synthesized by lichens on the growth, biomass accumulation and content of some macroelements in the organs of tomato plants are presented in this paper. The plants were grown hydroponically with (+)-usnic acid added to the media at various concentrations over a period of 21 days (from 10 days to 31 days after germination). At the highest subletal concentration of (+)-usnic acid (40 μM) under which the plants survived, the mean length of shoot, roots and leaf blade area attained about 13.6%, 11.5% and 0.5%, respectively, of the control values. In these conditions, the accumulation of dry matter was about 1.6%, 5.5% and 8.1% for leaves, stem and roots, respectively. The computed growth parameters (stem to roots, specific leaf weight and relative growth rate) were inversely proportional to the concentration of (+)-usnic acid in the medium, finally reaching a three to four times lower value than that determined in the control. Usnic acid reduced the content of the macroelements present in the plant tissues. In plants grown in media with an addition of 40 μM (+)-usnic acid, the macroelement content decreased by 25–35%, 48–55%, 65–69% and 60–70% for calcium, nitrogen, phosphorus and potassium, respectively, in comparison with the control.

Lead-Induced Histological and Ultrastructural Changes in the Leaves of Soybean (Glycine max (L.) Merr.)

The seedlings of the soybean (Glycine max. (L.) Merr.) cv. Polan were investigated by subjecting them to water culture for a period of 14 d. To the Knop nutrient solution, lead was added as PbCl2 at four concentrations: 0, 10, 20 and 40 mg dm−3. Observations of soybean leaf tissues were carried out by light microscopy, transmission electron microscopy and scanning electron microscopy. The Pb levels used in the present study reduced the area of cotyledons and leaf blades of the soybean plants. Pb-induced changes in the leaf epidermis structure involved a reduction in the cell size, more abundant wax coating, and an increase in the number of stomata and trichomes per unit area with simultaneous reduction in the size of the guard cells. The lead treatment resulted in the reduction in the thickness of the leaf blades, reduction in the area of xylem and phloem in the vascular bundles and in the diameter of the xylem vessels. Under Pb stress, the leaf mesophyll cells were characterized by the presence of altered chloroplasts with a reduced lamellar system and multidirectional pattern of the thylakoid system. Burst stroma of the thylakoid system and cracked chloroplast envelopes were also observed. The importance of the increase in the number of stomata and trichomes for plants under the metal stress was examined.