Periderm Thickness Research Articles

Effect of Persistent Salt Stress on the Physiology and Anatomy of Hybrid Walnut (Juglans major × Juglans regia) Seedlings.

Soil salinization has become one of the major problems that threaten the ecological environment. The aim of this study is to explore the mechanism of salt tolerance of hybrid walnuts (Juglans major × Juglans regia) under long-term salt stress through the dynamic changes of growth, physiological and biochemical characteristics, and anatomical structure. Our findings indicate that (1) salt stress inhibited seedling height and ground diameter increase, and (2) with increasing salt concentration, relative water content (RWC) decreased, and proline (Pro) and soluble sugar (SS) content increased. The Pro content reached a maximum of 549.64 μg/g on the 42nd day. The increase in superoxide dismutase (SOD) activity (46.80-117.16%), ascorbate peroxidase (APX) activity, total flavonoid content (TFC), and total phenol content (TPC) under salt stress reduced the accumulation of malondialdehyde (MDA). (3) Increasing salt concentration led to increases and subsequent decreases in the thickness of palisade tissues, spongy tissues, leaves, and leaf vascular bundle diameter. Upper and lower skin thickness, root periderm thickness, root diameter, root cortex thickness, and root vascular bundle diameter showed different patterns of change at varying stress concentrations and durations. Overall, the study concluded that salt stress enhanced the antireactive oxygen system, increased levels of osmotic regulators, and low salt concentrations promoted leaf and root anatomy, but that under long-term exposure to high salt levels, leaf anatomy was severely damaged. For the first time, this study combined the anatomical structure of the vegetative organ of hybrid walnut with physiology and biochemistry, which is of great significance for addressing the challenge of walnut salt stress and expanding the planting area.

Graphene oxide affected root growth, anatomy, and nutrient uptake in alfalfa

The increasing application of carbon nanomaterials has resulted in their inevitable release into the environment. Their toxic effects on plant roots require careful investigation. In the present study, alfalfa (Medicago sativa L.) was exposed to graphene oxide (GO) at levels of 0.2 %, 0.4 %, and 0.6 % (w/w) in potting soil. This study aims to better understand the impact of GO on the root growth, structure, and physiology of alfalfa in the soil matrix. The results demonstrated that GO significantly affected the development and structure of alfalfa roots, and the effect varied with GO level. The highest level of GO (0.6 %) reduced the root length, diameter, volume, dry weight, number of lateral roots, and root activity by 36.1 %, 31.3 %, 60.0 %, 89.6 %, 55.8 %, and 72.3 % (p < 0.05), respectively, and the vascular cylinder diameter, periderm thickness, vessel diameter, and phellem thickness decreased by 51.5 %, 50.7 %, 80.9 %, and 49.1 % (p < 0.05), respectively. These observations might be associated with GO-induced oxidative stress, which was indicated by the activity of antioxidant enzymes. Furthermore, high GO levels (0.4 % and 0.6 %) inhibited the uptake of N, P, K, Mg, Zn, Fe, Mo, Si, and B in roots. Our findings indicate that GO at high levels has a negative impact on root growth and development by inducing oxidative stress, structural impairment, and nutritional imbalance. Careful soil GO management should be emphasized.

Physiological, Anatomical, and Agronomic Responses of Cucurbita pepo to Exogenously Sprayed Potassium Silicate at Different Concentrations under Varying Water Regimes

Drought is one of the major environmental stresses that devastatingly impact squash development, growth, and productivity. Potassium silicate can attenuate the injuries caused by water stress. Hence, this study was designed to investigate the influence of three concentrations of potassium silicate; 10, 15, and 20 g/L on squash plants versus untreated control under three irrigation regimes; 100, 75, and 50% of estimated crop evapotranspiration (ET). The obtained results indicated that moderate (75% ET) or severe (50% ET) drought stress conditions gradually declined photosynthetic pigments, relative water content (RWC), mineral content, physiological parameters, and anatomical characteristics. These deleterious impacts were reflected on all growth and yield traits, i.e., plant height, fresh and dry weight of root and shoot, and fruit yield. On the other hand, the antioxidant enzyme activities; superoxide dismutase (SOD), catalase (CAT), and peroxidase (POX) significantly increased under severe drought stress at 50% ET followed by 75% ET. However, all evaluated exogenous applications of potassium silicate substantially enhanced photosynthetic pigments, RWC, N, P, and K content, antioxidant enzyme activities, and anatomical characters (periderm thickness, cortex thickness, midrib thickness, mesophyll thickness, number of xylem vessels per main vascular bundle, thickness of vascular bundle, thickness of collenchymatous tissue and upper epidermis, and thickness of collenchymatous tissue and lower epidermis). These desirable impacts were reflected in enhancing all growth and yield parameters. Conclusively, this study alludes that the exogenously applied of potassium silicate, particularly at 20 g/L, can alleviate the deleterious effects of drought stress and enhance the growth and productivity of squash plants, especially in arid environments.

Physical and mechanical properties of cassava (Manihot esculenta Crantz) cultivars: Implications for the design of mechanical peeling machines

AbstractThe data on physical and mechanical properties of short and long‐duration cassava cultivars are limited to design an efficient continuous type peeling machine for small‐scale processing. Short duration cultivars included Sree Jaya, Sree Vijaya, and Sree Swarna, as well as long duration cultivars included M‐4, Sree Athulya, Sree Suvarna, H‐226, Sree Raksha, Sree Pavithra, and Sree Vishakam, were investigated. The moisture content, girth, proximal diameter, middle diameter, cylindricity, and tuber surface taper angle were the highest for long‐duration cultivar H‐226. The maximum length was observed in the short‐duration cultivar Sree Swarna. The periderm thickness was the highest for Sree Suvarna, whereas the highest proximal cortex thickness, middle cortex thickness, and distal cortex thickness were observed in Sree Athulya, Sree Vijaya, and M‐4 cultivar, respectively. The highest bulk density, true density, and porosity were observed in the long‐duration cultivars; Sree Raksha, Sree Athulya, and Sree Suvarna, respectively. The highest hardness, shear force, and rupture force were recorded for cassava peelings in the cultivar Sree Athulya. Similarly for cassava flesh, the highest hardness, shear force, and rupture forces were recorded in the Sree Suvarna cultivar. A strong positive correlation for true density with bulk density and proximal diameter and moisture content with cylindricity and middle‐end diameter was found from the multivariate correlation analysis. Statistical analysis showed that the reported physical and mechanical properties of the cultivars were highly significant (p &lt;.01).Practical ApplicationsEngineering properties such as physical and mechanical properties are important for designing machines, storage structures, and processes. Cassava tuber peeling by the manual method is time‐consuming, labor‐intensive, and has a low capacity. Thus, the design of a peeling machine for small‐scale processing becomes important. The physical and mechanical characteristics of cassava flesh and peelings are critical design considerations for developing peeling machines for small‐scale processing. The physical and mechanical properties investigated here would provide technical and scientific data for designing continuous shearing type cassava peeling machine units such as tuber feeder length, peeling knife selection, peeling knife angle, and adjustable spring with required tension for holding rotary type peeling knife.

Structural Adaptation of Deverra tortuosa (Desf.) DC. to Its Natural Habitats in Egypt

DEVERRA tortuosa (Desf.) DC. is a common medicinal, grazing, and salt-tolerant desert plant that can grow in a variety of habitats. The current study aims to detect anatomical adaptation to stress factors in different organs of the D.tortuosa plant (salinity, and drought). The plant was collected in Egypt from 17 different locations representing seven different habitats (sand dunes, sand flats, salt marshes, wadi bed & slope, roadsides and cultivated lands). The effect of soil factors (soil texture, pH, EC, and organic matter) on the anatomical features of various plant organs (root, stem, and leaf) was investigated. Variations in plant anatomical features were observed in response to significant differences in soil parameters (EC, organic carbon, and ionic content) between desert habitats. According to CCA analysis, periderm thickness is correlated with changes in ion concentrations (Ca+2, K+, and Na+), whereas cortex width is correlated with changes in pH and organic matter content in roots. Meanwhile, the degree of salinity in the habitats is correlated with sclerification in the stem and the widest chlorenchyma cells. Thick epidermis and a large xylem area are required for salt excretion in leaf development, and water conservation is related to changes in moisture content. Reducing plant water loss in the studied desert habitats could explain D. tortuosa’s successful growth and survival under such harsh conditions.

Root structural plasticity enhances salt tolerance in mature olives

Roots are the first plant organ to encounter, sense, and respond to soil salinity. Like for many moderately salt tolerant species, roots of olive (Olea eurpaea) trees are the principal players in salt tolerance. We studied roots of mature olive trees in order to illuminate the yet vague mechanism(s) of root salt exclusion.Root structural traits were examined in olive trees grown in lysimeters and from a long-term salinity field trial. The distribution of salts was detected in root cross-sections using scanning electron microscopy combined with energy dispersive spectroscopy.Increased soil salinity caused a continuous decline in specific root length and an increase in root diameter, periderm thickness, and specific hydraulic conductivity. While periderm cell number was not modified, cell diameter increased linearly by a total of 50 % as root zone salinity increased nearly eight-fold. Strong compartmentation of Na within the periderm was found, with highest content in the outer periderm layer and lowest content in the stele. Increase in soil salinity was associated with decrease in stele area, yet, hydraulic conductivity was doubled due to higher fraction of large diameter xylem vessels.Our results indicate significant root structural plasticity, which underlies the salt resistance mechanisms. The dominant trait enabling salt tolerance of olive trees is the enlarged periderm serving as an apoplastic barrier that enhances salt compartmentation and exclusion from the vascular tissues.

ECOPHYSIOLOGY OF THE TREE SPECIES Cedrela fissilis Vell. (Meliaceae) SUBMITTED TO FLOODING

ABSTRACT Soil water saturation requires different adaptative strategies by tree species that live under such conditions. We aimed to study the responses that ensure flooding tolerance by tree species and so provide support for recovery projects with degraded areas subject to flooding. We evaluated the ecophysiology of Cedrela fissilis under different water saturations, including anatomical traits, gas exchange parameters, antioxidant system analysis and growth. We subjected 100 day-old plants to three treatments: Control (FC) where the substrate was kept at field capacity; Flooded Roots (FR), where the substrate remained submerged but with no surface layer of water, and Flooded Stem (FS), with a water layer accumulation of around 3.0 cm over the substrate, flooding part of the stems. The plants were kept under such conditions for 90 days. Plants survived in all treatments due to a marked development of cortical intercellular spaces in flooded plants. However, photosynthesis and other gaseous exchange were limited under FR and FS treatments. In addition, the periderm thickness was reduce by flooding and there was an accumulation of starch grains in the parenchyma cells of the xylem, cortex and pith of the stem. There was also a significant lipid peroxidation on the leaves under FR and FS treatments. The superoxide dismutase activity was decreased, but the activities of the ascorbate perioxidases and catalase in the leaves were increased. We concluded that young Cedrela fissilis plants partially tolerate flooding since they developed ecophysiological changes in order to survive in this condition. Consequently, this species is a good candidate for the reforestation projects in environments where intermittent flooding occurs, such as riverside and riparian forests.

Anatomical Adaptations to Salinity in Spergularia marina (Caryophyllaceae) from Turkey

The present paper deals with the salt effect on root, stem and leaf anatomy of Spergularia marina. Salt tolerant populations of Spergularia marina from low (2.0–4.2 dS/m), medium (9.3–10.7 dS/m) and highly (18.4–26.2 dS/m) saline soils were evaluated for anatomical modifications. Root anatomical characteristics as cortex thickness and xylem vessel diameter were decreased in high saline environments. Increased aerenchyma and periderm thickness in the root were critical for checking water loss and enhancing water storage capability. In stem, higher salinity decreased the thickness of the epidermis and cortex. Increased aerenchyma and increased thickness of vascular tissue seemed to be crucial for its better survival under saline environments. The thickness of sclerenchyma was unchanged under low and moderate salinity but considerably increased under high salinity. Leaf anatomy shows that salt stress resulted in an increase of cuticle and parenchyma thickness as well as an increase of vascular bundle sheath thickness. The presence of the cells with calcium oxalate crystals in the stem and leaf increased at higher salinity. Additionally, under high salinity it was observed that both stomatal index and stomatal dimensions were considerably reduced. These results show that salinity stress shows significant anatomical modifications in Spergularia marina.

Adaptive plasticity of Laguncularia racemosa in response to different environmental conditions: integrating chemical and biological data by chemometrics

Mangroves are dynamic environments under constant influence of anthropic contaminants. The correlation between environmental contamination levels and possible changes in the morphology of plants, evaluated by multivariate statistics helps to highlight matching between these variables. This study aimed to evaluate the uptake and translocation of metals and metalloids in roots and leaves as well as the changes induced in both anatomy and histochemistry of roots of Laguncularia racemosa inhabiting two estuaries of Espírito Santo (Brazil) with different pollution degrees. The analysis of 14 elements in interstitial water, sediments and plants followed by multivariate statistics, allowed the differentiation of studied sites, showing good match between levels of elements in the environment with the corresponding in plants. L. racemosa showed variations in their root anatomy in different collection areas, with highest values of cortex/vascular cylinder ratio, periderm thickness and air gap area in Vitória Bay, the most polluted sampling area. These three parameters were also important to differentiate the mangrove areas by linear discriminant analysis. The development stage of aerenchyma in roots reflected the oxygen availability in the water, being found a negative correlation between these variables. The combined use of chemical and biological analyses responded quite well to different pollution scenarios, matching morphological responses to physical and chemical parameters, measured at different partitions within the estuary. Thus, L. racemosa can be confirmed as a reliable sentinel plant for biomonitoring of estuaries impacted by anthropic pollution.

Comparison of root anatomy and xylem vessel structure in rain-fed and supplementary irrigated ‘Yaghooti-Syah Shiraz’ grapevine (Vitis vinifera L.)

Changes in environmental conditions may lead to modifications in structural development of plant root. Effects of supplementary irrigation and soil depths (0–90 cm) on anatomical changes in xylem were investigated in rain-fed Vitis vinifera L. cv. Yaghooti-Syah Shiraz. Irrigated and control roots were prepared according to routine histological procedure. Light microscopic observations revealed the structural features of drought tolerant control roots and their changes after the treatment. Irrigated roots were characterized by the absence of starch grains in parenchyma cells, uniformity of parenchymatous pith cells, and a decrease in periderm thickness. Morphometric investigation of xylem showed that irrigated and deep roots had larger mean and maximum vessel diameter and fewer vessel number than rain-fed and shallow roots, at every soil depth of every treatment. Secondary xylem vessel diameter and number were more affected by irrigation and soil depths than metaxylem. Grape roots responded to supplementary irrigation and increasing soil depth by reducing protective and supporting tissues and increasing vessel diameter.

Atributos Morfológicos de Tubérculos en Genotipos de Solanum Phureja Juz et Buk y su Relación con la Incidencia de la Sarna Polvosa

&lt;p&gt;El objetivo de este trabajo es determinar si existe relación entre las características morfológicas de genotipos de &lt;em&gt;Solanum phureja &lt;/em&gt;de la colección de trabajo de la Universidad Nacional de Colombia y la respuesta al ataque de la sarna polvosa en tubérculos. Se evaluaron 93 genotipos y de cada uno se cosecharon diez tubérculos en el municipio de La Unión (Ant). Se determinó la densidad y el área de las lenticelas, el grosor de la peridermis, el color y forma de los tubérculos. Los datos obtenidos se confrontaron con la información de la incidencia de la sarna polvosa en tubérculos, bajo condiciones de campo. Se encontró que existe una amplia variabilidad genética en la colección evaluada para todas las características morfológicas de tubérculos. Los tubérculos de color negro presentaron mayor densidad y área de lenticelas y el menor grosor de peridermis, mientras que los genotipos rojizos presentaron menores densidades y área de lenticelas y valores intermedios para el grosor de la peridermis. Por otro lado los tubérculos alargados presentan mayor densidad de lenticelas y menor grosor de peridermis, mientras que los tubérculos ovalados presentan el comportamiento contrario. Igualmente se encontró que los tubérculos redondos presentaron bajos valores de densidad de lenticelas y grosor de la peridermis. No se encontró relación entre las características morfológicas evaluadas y la incidencia de la sarna polvosa en campo.&lt;/p&gt;

Auxin-Induced Resistance to Common Scab Disease of Potato Linked to Inhibition of Thaxtomin A Toxicity.

Production of the phytotoxin thaxtomin A by pathogenic Streptomyces spp. is essential for induction of common scab disease in potato. Prior studies have shown that foliar application of sublethal concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D) and other auxin or auxin-like compounds significantly reduced severity and occurrence of common scab in subsequently produced tubers. However, the means of disease suppression by these compounds was not known. We confirm the disease suppressive activity of 2,4-D. Detailed tuber physiological examination showed that lenticel numbers, lenticel external dimensions, and periderm thickness and structure, physiological features believed to be critical to Streptomyces scabiei infection, were not substantially changed by 2,4-D treatments, negating a possible mechanism for disease suppression through alteration of these structures. In contrast, our studies show accumulation of 2,4-D in tubers of treated plants occurs and is associated with an enhanced tolerance to thaxtomin A. Applying 2,4-D to cultures of S. scabiei did not significantly alter in vitro growth of the pathogen. Thaxtomin A production by the pathogen was inhibited by 2,4-D, but only at the highest rate tested (1.0 mM), which is at least 200-fold more than is found in 2,4-D treated tubers. These data suggest 2,4-D has no direct effect on the pathogen or its virulence. Confirmatory evidence from studies with Arabidopsis thaliana seedlings demonstrated that the auxins 2,4-D and IAA ameliorate thaxtomin A toxicity. The evidence presented whereby auxin treatment inhibits toxicity of thaxtomin A secreted by the pathogen suggests a novel indirect means of disease suppression.

The Histology of Hybrid Poplar Clones Inoculated with Septoria musiva.

Septoria musiva causes stem cankers that severely limit production of susceptible hybrid poplars in eastern North America. A field experiment was conducted with resistant clone DN34 and susceptible clone NC11505 in order to (i) identify tissues colonized by the pathogen, (ii) describe tissue responses to S. musiva, and (iii) determine whether tissue responses to S. musiva differed between hybrid poplar clones. Branches of each clone were inoculated by removing the fourth or fifth fully expanded leaf and placing an agar plug colonized by an aggressive isolate of S. musiva over the wound. Seven weeks after inoculation, branches were harvested and prepared for histology. Data from nonwounded control, wounded control, and wounded and inoculated stems were collected and analyzed for effects of clone and treatment. In general, fungal colonization was more extensive in NC11505 and exophylactic and necrophylactic periderms (NPs) of clone DN34 were significantly thicker than those of NC11505, regardless of treatment. The number of NPs produced and the distance from the epidermis to the outermost layer of phellem were significantly affected by the pathogen. Inoculated stems of clone DN34 developed a single NP that formed closer to the wound surface than in wounded controls. In contrast, inoculated stems of NC11505 developed successive NPs and the first NP formed further from the wound surface than in wounded controls. These two host responses to inoculation, as well as measures of exophylactic and necrophylactic periderm thickness, may be useful as markers for the selection of poplar resistant to damage by S. musiva.

Influence of mefluidide on tuber development, maturity, and storage of Russet Burbank and Norland potatoes

Mefluidide {N-[2,4-dimethyl-5-[[(trifluoromethyl) sulfonyl] amino] phenyl] -acetamide}, a chemical with plant growth regulator properties, was applied to the foliage of potatoes (Solanum tuberosum L.) in field experiments to determine its effects on tuber development, maturity, and storage of the cultivars Russet Burbank and Norland. The rate of sucrose loss before harvest was reduced in mefluidide-treated plants. Total and marketable yields generally were lower in treated plants. Specific gravity tended to increase in Russet Burbank with application rates up to 1.0 kg ai/ha mefluidide. Preharvest treatments of mefluidide resulted in an increase in periderm thickness and russeting. However, weight loss during storage was greater in tubers from treated plants. Less sprouting occurred in storage in tubers from mefluidide-treated plants. Mefluidide resulted in a lower anthocyanin content and consequently an undesirable color change in Norland tubers.

Analysis of variation in leaf and twig characters of Abies lasiocarpa and A. amabilis from north-coastal British Columbia

To investigate the extent and causes of natural variation within and among populations of Abies amabilis and Abies lasiocarpa collected from north-coastal British Columbia, morphological and anatomical data were analyzed using principal components analysis, canonical analysis, and regression analysis. The results indicate that hybridization does not occur between these two species, even in areas modified by natural or artificial disturbance. Within A. lasiocarpa there is an indication of evolutionary divergence of populations correlated with latitude and (or) local environmental conditions. Specimens of A. lasiocarpa and A. amabilis collected from a lava bed were found to be differentiated from forest-grown populations, apparently as a result of either phenotypic plasticity or local selection pressures affecting the survival of newly established seedlings. Regression analysis demonstrated that twig periderm thickness in A. amabilis correlates significantly with altitude suggesting the presence of clinal variation.

Sweetpotato Periderm Failure in Response to Soil Moisture and Temperature1

Abstract Results of tests to evaluate periderm peeling and failure forces of container-grown roots of sweetpotato (Ipomea batatas, Lam. cv. Nemagold), conditioned to various environments, were erratic. With field-grown roots, peeling and failure forces varied with soil temperature and soil moisture and were generally highest for warm dry conditions. Temperature and moisture had approximately equal effects on periderm peeling resistance within the ranges tested. Periderm thickness decreased and peeling resistance increased as soil temperature increased, but the number of cell layers remained fairly constant.

Susceptibility of potato varieties to skin spot (Oospora pustulans) in relation to the structure of the skin and eye

Tubers of 30 commercial potato varieties, grown in two different soils, were inoculated withOospora pustulans and incubated in two different conditions in two successive years. Varietal differences in skin and eye susceptibility were in general agreement with those previously recorded in field experiments. There was no consistent varietal difference in symptom expression but in some cases a superficial or slightly depressed skin neerosis developed in addition to the normal pustules. Over all the varieties, there was a significant correlation between surface and eye infection. Skin infection was little influenced by the temperatures of incubation which fluctuated over the range 33–50 F (0.6–10 C). Eye infection tended to be lower where the maximum temperature was higher. Thickness of the tuber periderm and of the suberised layer, and the content of crude fibres in the periderm were all negatively correlated with susceptibility to skin infection. No obvious relation was found between the structure of the eyes and susceptibility to eye infection. The two types of soil used did not influence any of the periderm characters observed or skin or eye susceptibility to skin spot. In the 9 varieties tested, immature and mature tubers showed no significant difference in mean skin susceptibility or in mean periderm thickness.