Anatomical Changes In Roots Research Articles

Anatomical changes, osmolytes accumulation and distribution in the native plants growing on Pb-contaminated sites.

Native plants growing on heavy-metal-contaminated sites are the potential candidates for phytoremediation of contaminated sites due to their tolerance and adaptation to toxic environment. For better application of the technology, in-depth knowledge and understanding of the anatomy and physiology of these plant species are essential. In this study, anatomical changes in roots and leaves of various plant species growing on Pb-contaminated sites as well as osmolytes (proline, PR; glycine betaine, GB; and phenolics, PH) production and distribution in different plant parts were investigated. The soil and plant samples were collected in triplicates from two different Pb-contaminated sites, while control plants were collected from the University of Ibadan. The plants were washed and partitioned into different parts for anatomical and biochemical studies, and soil adhering to the roots of different plant species was collected for the determination of Pb contents. Sporobolus pyramidalis, Cynodon dactylon, Imperata cylindrica, Eleusine indica, Gomphrena celosioides, Rhinconspora corymbosa and Echinochloa colona are the plant species common to these contaminated sites. Though with variations based on the site, thick epidermis and sclerenchyma, pronounced and numerous vascular bundles as well as trichomes were some of the anatomical characteristics of these metallophytes from contaminated sites compared to their counterparts from uncontaminated site. These plants also produced PR, GB and PH, with PH being the highest followed by PR and GB. Accumulation in different parts of the plants also varied depending on the plant species and the osmolyte. They were more in the leaf than other plant parts. Among the plant species, Sporobolus pyramidalis had the highest value of proline (3.26 and 2.63µg/g FW) and glycine betaine (3.44 and 2.23µg/FW) in the leaf and stem, respectively, followed by Cynodon dactylon having 2.20 and 0.89µg/g FW proline and 2.02 and 0.94µg/g FW glycine betaine. On the Pb accumulation in plant, more lead (Pb) was found in the roots than other plant parts. Gomphrena celosioides accumulated the highest Pb (4537.50 and 1081.50mg/kg) in the root and shoot, respectively, followed by Eleusine indica (3988 and 699.00mg/kg), while the lowest values were recorded for Echinochloa colona (36.87 and 5.97mg/kg). In rhizospheric soils, G. celosioides had the highest Pb content (34,405.00mg/kg) which was higher than other rhizospheric soils. In conclusion, phenolics were produced more in these metallophytes and all the osmolytes were more in leaf than root. Anatomical modifications in response to heavy metal exposure differed between plant species and level of contamination. Lead accumulation in plant also varied depending on plant species.

Quantification of cliff retreat in coastal Quaternary sediments using anatomical changes in exposed tree roots

AbstractSea cliffs represent 80% of the world's coasts and can be found virtually in all types of morphogenetic environments. Most studies on rocky environments focused on the impacts of modern sea level rise on cliff stability derived from sequential surveys, direct measurements or erosional features in anthropogenic structures. In this study, we explore the potential of dendrogeomorphic techniques to quantify multidecadal changes in coastal environments on Porquerolles Island (France). We sampled a total of 56 cross‐sections from 16 Pinus halepensis Mill. roots growing on former alluvial deposits and on sandy‐gravelly cliffs to quantify mean annual cliff retreat rates as well as changes in cliff geometry. Anatomical changes in roots have been used successfully in the past to quantify continuous denudation rates on slopes, channel incision and gullying processes but the approach has not been used so far in a coastal cliff context. At Porquerolles Island, reconstructed rates of cliff retreat cover 30–40 years and show average erosion rates between 0.6 and 3.9 cm yr−1 (average: 2.1 cm yr−1). Highest rates are observed at Pointe de la Tufière (2.6–3.9 cm yr−1), a small rock promontory that is more exposed to wave and storm surges than the remainder of the study area. By contrast, lower erosion rates are recorded at cliffs protected by the La Courtade pocket beach (0.6–1.9 cm yr−1). This contribution demonstrates that dendrogeomorphic analyses of roots clearly have a significant potential and that they are a powerful tool for the quantification of multidecadal rates of cliff retreat in areas where measurements of past erosion are lacking. More specifically, the approach also has clear advantages over the shorter time series obtained with repeat monitoring (e.g. terrestrial laser scanning, sensors, erosion pins) or over longer, but more coarsely resolved records obtained from aerial photographs or radio‐nuclides. © 2018 John Wiley & Sons, Ltd.

Cambios anatómicos en raíces e hipocótilos de plántulas de Prosopis ruscifolia (Fabaceae) sometidas a estrés salino

Prosopis ruscifolia is a pioneer tree species in flooding or saline areas. The aim of this work was to assess anatomical changes in roots and hypocotyls of P. ruscifolia seedlings induced to saline stress under controlled conditions. Seeds, collected in natural forests of Western Chaco region in Argentina, were sown on paper towels moisturized with saline solutions of 100, 200 and 300 mM of NaCl, and a control group with distilled water. Four repetitions of 50 seeds per treatment were sown, located in hermetic polystyrene boxes, and included in a seeding chamber, at 27 ºC and 12 hours photoperiod. Were studied 35 seedlings from each saline concentration; these seedlings were processed 12 days after sown to obtain microscopic samples. The anatomical variables measured in roots and hypocotyls were the following: main root diameter (µm), bark thickness (µm), number of cell strata in bark, central cylinder diameter (µm), pith diameter (µm), number of cell strata in the pericycle and the tangential diameter of vessels (µm). ANOVA analysis were performed with hypocotyl and root diameters as the dependent variable, and bark thickness (µm), number of cell strata in the bark, the central cylinder diameter (µm), the pith diameter (µm), number of cell strata in the pericycle, the tangential diameter of vessels and the saline concentration as independent variables. Results showed that the root diameter decreased with increasing saline concentrations (P < 0.0001). The bark thickness decreased at 100 mM (P < 0.0001) and the number of cell strata of bark increased to 300 mM (P < 0.0002). The central cylinder diameter decreased at 100 mM saline concentration (P < 0.0001) and the number of cell strata of the pericycle and the pith diameter reduced progressively until 300 mM. The tangential diameter of vessels decreased at 300 mM. These anatomical changes suggested alterations in the expansion and cell division caused by the salinity, and could limit lateral roots formation and reserves storage. Hypocotyls did not show significant anatomical changes in response to increasing salinity, with exception of stomata position and an increase of the hypodermis thickness. These changes indicated that the water stress imposed by low osmotic potential is caused by increasing saline concentration. The seedlings of P. ruscifolia experienced anatomical changes in response to tested saline concentrations in traits related to reserve storage, the absorption and conduction of water, and lateral roots formation.

English

The current study was undertaken to determine the effects of arsenic on&nbsp;Colocasia esculentum. Rhizomes were grown in pots containing 2.5 kg of garden soil with increasing concentration of arsenic. Arsenic accumulation was more in shoots compared to roots at higher concentrations. High arsenic concentration caused reduction in plant growth along with induction of few antioxidants.&nbsp;C. esculentum&nbsp;has a strong antioxidative and physiological defense mechanism. Under arsenic stress, an increase in catalase, peoxidase, few non-enzymatic antioxidants and an induction of few stress induced protein were observed, along with some anatomical changes in roots.&nbsp;The increase in antioxidant stress enzyme activities in response to&nbsp;arsenicexposure may be taken as evidence for an enhanced detoxification capacity of&nbsp;C. esculentum,&nbsp;a herbaceous monocot&nbsp;plant, towards reactive oxygen species (and derivatives) that might be generated in the stressed plants. Key words:&nbsp;Arsenic,&nbsp;Colocasia esculentum, antioxidant, metal, root

Ecophysiological and anatomical changes due to uptake and accumulation of heavy metal in Brachiaria decumbens

The growth and developmental characteristics of grasses and their high biodiversity make such plants suitable for remediation of areas contaminated by heavy metals. Nevertheless, heavy metal toxic effect on the plants may cause alteration in their metabolic pathways, such as photosynthesis, respiration, and growth, modifying plant anatomy. This work aimed to evaluate the effect of levels of soil contamination (0, 7.5 % and 15 % m³ m-3) on biomass production, on photosynthetic characteristics and on anatomical changes in roots and leaves of brachiaria (Brachiaria decumbens Stapf.). After seeds were planted, seedlings were uprooted and replanted in vases containing soil at different contamination levels, being left to rest for 120 days. At the end of that time, plants presented reduced yield of root and shoot dry matter, contents of chlorophyll a, chlorophyll b, total chlorophyll and potential photosynthesis with increased of soil contamination. The cell layers of endodermis and exodermis in the root tissues and the cell walls of the xylem and cortical parenchyma all thickened as contamination increased. In the leaf tissues, the adaxial and abaxial epidermis presented increased thickness while the leaf blade presented reduced thickness as contamination increased with consequent change in the root growth rate. In general, the effects of heavy metal increased with the metal concentration. Some results indicate that B. decumbens seems to have some degree of heavy metal tolerance.

Anatomical Development of Cell Structure Including Casparian Strip during Root Growth in Grapevines

Morphological and anatomical changes in roots associated with their development were investigated in grapevines. When new roots initiated from the suberized structural root in grapevines, the tip of the root expanded outward and the suberized outer layer was detached from the surface of the root tip. At the onset of root initiation, the cell nucleus reappeared in the apical meristem, and cell division occurred. Once approximately five xylem vessels per pole had appeared, the Casparian strip appeared as a dot in the center of the radial wall of the endodermis. At a point 150 mm from the root tip, the endodermis was completely suberized and the number of xylem vessels per pole increased. In younger roots, suberization of the exodermis was observed earlier than in the endodermis, although the Casparian strip could not clearly be detected in the exodermis. As the root aged, a gap formed between the endodermis and pericycle. Before the endodermis was sloughed off from pericycle layers, cell division was observed in the pericycle and the suberized pericycle layers increased.

Morphophysiological responses and programmed cell death induced by cadmium in Genipa americana L. (Rubiaceae)

Cadmium (Cd) originating from atmospheric deposits, from industrial residues and from the application of phosphate fertilizers may accumulate in high concentrations in soil, water and food, thus becoming highly toxic to plants, animals and human beings. Once accumulated in an organism, Cd discharges and sets off a sequence of biochemical reactions and morphophysiological changes which may cause cell death in several tissues and organs. In order to test the hypothesis that Cd interferes in the metabolism of G. americana, a greenhouse experiment was conducted to measure eventual morphophysiological responses and cell death induced by Cd in this species. The plants were exposed to Cd concentrations ranging from 0 to 16 mg l(-1), in a nutritive solution. In TUNEL reaction, it was shown that Cd caused morphological changes in the cell nucleus of root tip and leaf tissues, which are typical for apoptosis. Cadmium induced anatomical changes in roots and leaves, such as the lignification of cell walls in root tissues and leaf main vein. In addition, the leaf mesophyll showed increase of the intercellular spaces. On the other hand, Cd caused reductions in the net photosynthetic rate, stomatal conductance and leaf transpiration, while the maximum potential quantum efficiency of PS2 (Fv/Fm) was unchanged. Cadmium accumulated in the root system in high concentrations, with low translocation for the shoot, and promoted an increase of Ca and Zn levels in the roots and a decrease of K level in the leaves. High concentrations of Cd promoted morphophysiological changes and caused cell death in roots and leaves tissues of G. americana.

Salt-induced changes in the vegetative anatomy ofProsopis strombulifera(Leguminosae)

Seedlings of Prosopis strombulifera (Lam.) Benth. were grown hydroponically in Hoagland's solution with addition of 25 mmol/L NaCl every 48 h until final salt concentrations of 250, 500, and 700 mmol/L were reached. Control plants were grown without salt. Salinity induced anatomical changes in roots (young and mature zones), hypocotyls, young stems, and leaflets. The diameters of the young zone of roots of plants grown in increasing salt concentrations were smaller than those of controls, with reduced number of cortex layers and reduced size of the vascular system. The roots from tolerant plants showed precocious suberization and (or) lignification of the endodermal cells and early activity of the pericycle. Hypocotyl diameter was reduced along with a reduction in secondary phloem. Roots and hypocotyls showed abundant phellem formation. The stem diameter of young tolerant plants was notably diminished and less tissue lignification occurred. In stems and leaflets of treated plants, NaCl stimulated the production of tannins. In the leaflets, vascular bundles were similar in size. Groups of elongated parenchyma cells with many chloro plasts surrounded the bundles. These results suggest that in the absence of secretory organs, the anatomical modifications in this species are related to metabolic adaptations, such as an early development of the endodermal barrier for ion exclusion, to allow survival in high salinity.Key words: Prosopis strombulifera, anatomical changes, hydroponics, NaCl.

Effect of ozone and aluminum on pitch pine (Pinusrigida) seedlings: anatomy of mycorrhizae

Newly germinated pitch pine (Pinusrigida Mill.) seedlings inoculated with a mycorrhizal fungus (Pisolithustinctorius (Pers.) Coker &amp; Couch) were grown for 13 weeks in sand irrigated with nutrient solution (pH 4.0) containing 0, 12.5, 25, or 50 mg/L aluminum (Al) in growth chambers fumigated with 0, 50, 100, or 200 ppb ozone. Anatomical changes in roots stressed by ozone and Al, singly and in combination, were determined by light and electron microscopy. All ozone concentrations reduced the percentage of mycorrhizal colonization. In contrast, Al increased the percentage of colonization at low concentration, reducing it only at the highest level. Aluminum caused more overall deterioration of root cortex than ozone, though both treatments adversely affected the mycorrhizal fungus. Increased vacuolation in the root meristem was caused by both ozone and Al. Additional effects of ozone on cells in the meristem were the swelling of the nuclear membrane and invaginations in the plasmalemma. Intracellular fungal hyphae were observed at the highest level of ozone and (or) Al. The combined effect of ozone and Al on the anatomy of mycorrhizae was greater (possibly synergistic) than the effect of each pollutant alone. Similar cellular alterations have also been observed in forests damaged by pollution.