Silicon Differently Affects Apoplastic Binding of Excess Boron in Wheat and Sunflower Leaves

Monocots and dicots differ in their boron (B) requirement, but also in their capacity to accumulate silicon (Si). Although an ameliorative effect of Si on B toxicity has been reported in various crops, differences among monocots and dicots are not clear, in particular in light of their ability to retain B in the leaf apoplast. In hydroponic experiments under controlled conditions, we studied the role of Si in the compartmentation of B within the leaves of wheat (Triticum vulgare L.) as a model of a high-Si monocot and sunflower (Helianthus annuus L.) as a model of a low-Si dicot, with the focus on the leaf apoplast. The stable isotopes 10B and 11B were used to investigate the dynamics of cell wall B binding capacity. In both crops, the application of Si did not affect B concentration in the root, but significantly decreased the B concentration in the leaves. However, the application of Si differently influenced the binding capacity of the leaf apoplast for excess B in wheat and sunflower. In wheat, whose capacity to retain B in the leaf cell walls is lower than in sunflower, the continuous supply of Si is crucial for an enhancement of high B tolerance in the shoot. On the other hand, the supply of Si did not contribute significantly in the extension of the B binding sites in sunflower leaves. © 2023 by the authors

Methods for the assessment of background limits of Cd and Cr in the soil of Moravicki district

У раду су приказане различите методе одређивања границе природ ног садржаја Cr и Cd у земљишту Моравичког округа. Дистрибуција садр жаја испитиваних елемената је десно асиметрична, са високом дисперзијом, посебно садржаја Cr. Применом графичких метода (кумулативна крива–CDF и boxplot) добијене су границе природног садржаја за Cd 1,40 mg kg-1, и за Cr око 230 mg kg-1. За емпиријске методе коришћени су природни подаци и ло гаритамски трансформисани, при чему су добијене знатно веће вредности него у природној симулацији. Граничне вредности добијене различитим ме тодама се разликују. Карте показују да највећи део територије има релативно ниске концентрације испитиваних елемената чије границе природног садр жаја највише одговарају вредностима израчунатим методом [Median±2MAD] и ниже. На деловима територије са повећаним садржајима погодније су ра чунске методе [Mean±2Sd] и boxplot–обрачун горњег прага. Дате су границе природног садржаја за поједине хомогене геохемијске целине

Average leaf concentrations of the major soil polluting elements (S, Fe, Cu and Al) in the three major ecological groups of species along the induced soil gradient.

<p>Leaf Al concentrations are separately shown for two key species dominant on severely degraded soils (f). Species groups are defined by Indicator Species Analysis (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0114290#pone-0114290-g002" target="_blank">Figure 2</a>). Average group elemental concentrations were calculated by weighting the concentrations in each species by the relative proportion of a species in group biomass per m². Leaves were sampled when crop was at milky ripeness phase (Z71–75).</p

Response of the major groups of weeds to the pollution-induced soil gradient.

<p>Species envelope curves along the main ordination axis after NMS ordination of untransformed (a–c) and relativized (d–f) abundances are shown. Groups are defined after Indicator Species Analysis (IV>30%, <i>P</i><0.01) and subsequent classification (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0114290#pone-0114290-g002" target="_blank">Figure 2</a>). Species indicating relatively unaltered calcareous soil (a, d); species of broad valence dominant in the middle portions of the soil gradient (b, e); species indicating most severely altered, nutrient-poor acidic soils (c, f). NMS axes are scaled in standard deviations from the centroid in a normalized configuration. Relative abundance - % of the sum of OTV values in a sample.</p

Major ecological adaptations of weed vegetation along the soil gradient.

<p>Ellenberg Indicator Values (a); life form spectra (b); chorological spectra (c). Parameters are weighted by the species cover-abundance (OTV). Weighted mean values + SD marked by the same letter in each colour-coded category are not different at <i>P</i><0.05.</p

Assembly Processes under Severe Abiotic Filtering: Adaptation Mechanisms of Weed Vegetation to the Gradient of Soil Constraints

<div><p>Questions</p><p>Effects of soil on vegetation patterns are commonly obscured by other environmental factors; clear and general relationships are difficult to find. How would community assembly processes be affected by a substantial change in soil characteristics when all other relevant factors are held constant? In particular, can we identify some functional adaptations which would underpin such soil-induced vegetation response?</p><p>Location</p><p>Eastern Serbia: fields partially damaged by long-term and large-scale fluvial deposition of sulphidic waste from a Cu mine; subcontinental/submediterranean climate.</p><p>Methods</p><p>We analysed the multivariate response of cereal weed assemblages (including biomass and foliar analyses) to a strong man-made soil gradient (from highly calcareous to highly acidic, nutrient-poor soils) over short distances (field scale).</p><p>Results</p><p>The soil gradient favoured a substitution of calcicoles by calcifuges, and an increase in abundance of pseudometallophytes, with preferences for Atlantic climate, broad geographical distribution, hemicryptophytic life form, adapted to low-nutrient and acidic soils, with lower concentrations of Ca, and very narrow range of Cu concentrations in leaves. The trends of abundance of the different ecological groups of indicator species along the soil gradient were systematically reflected in the maintenance of leaf P concentrations, and strong homeostasis in biomass N:P ratio.</p><p>Conclusion</p><p>Using annual weed vegetation at the field scale as a fairly simple model, we demonstrated links between gradients in soil properties (pH, nutrient availability) and floristic composition that are normally encountered over large geographic distances. We showed that leaf nutrient status, in particular the maintenance of leaf P concentrations and strong homeostasis of biomass N:P ratio, underpinned a clear functional response of vegetation to mineral stress. These findings can help to understand assembly processes leading to unusual, novel combinations of species which are typically observed as a consequence of strong environmental filtering, as for instance on sites affected by industrial activities.</p></div

The mass ratio of N:P in weed vegetation and cereal crops along the soil pollution gradient.

<p>Leaf N:P along the complex soil gradient indicated by the pollution load (a); leaf N:P along the decreasing plant available P concentrations in polluted soils (b); biomass N:P in weed vegetation as a function of soil N:P ratio (c). <i>H</i> - regulatory coefficient, slope of the linear trend line. Leaf N and P concentrations are weighted by the relative proportion of a species in total biomass per m², sampled when crop was at milky ripeness phase (Z71–75).</p

Unconstrained ordination (NMS) of weed samples along the transects in cereal fields partially damaged by mine tailings.

<p>Data matrix: 84 species (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0114290#pone.0114290.s005" target="_blank">Table S4</a>) in 100 samples, maximal species abundances (OTV) recorded during 2 months-survey. Unrelativized OTV (a); relativized OTV (b). The values in parentheses denote the proportion of variance represented by each axis. Superimposed soil variables correlated by more than 10% with weed samples ordination are shown. The angles and lengths of the radiating lines indicate the direction and strength of relationships of the soil variables with the ordination scores. Crosses denote group centroids.</p

Visual symptoms in the cereal crops as a basis for sampling along the spatial gradient on soils affected by pyritic Cu tailings.

<p>−, none; +, low; ++, moderate; +++, severe.</p><p>Relative yield reduction was measured <i>a posteriori</i>.</p><p>Visual symptoms in the cereal crops as a basis for sampling along the spatial gradient on soils affected by pyritic Cu tailings.</p

Gradients in cereal fields partially damaged by the deposition of mining waste.

<p>Arrows indicate the direction of the increasing deposition of mining waste. Soil gradient before crop emergence (a); Zone 3, Cluster B weeds, facies with <i>Consolida regalis</i> (violet flowers) (b); Zone 4, Cluster C weeds, facies with <i>Persicaria lapathifolia</i>; 1 m×1 m quadrat for biomass harvest is shown (c); Zone 3, Cluster B, facies with <i>Papaver rhoeas</i> (red flowers) (d). <i>Rumex acetosella</i>, <i>Agrostis capillaris</i> and <i>Persicaria lapathifolia</i> can be observed at the highest soil pollution levels (the “green band”, marked by dashed line; b, c and d).</p