Root Morphology, Anatomy, and Mycorrhiza of Peristylus goodyeroides (D.Don) Lindl. (Orchidaceae) in Different Life Stages: Ecological Significance and Implication for Conservation

Orchid roots have vital functions for water absorption, nutrient uptake, a place of symbiosis with mycorrhizal fungi, adaptation, and survival. The aim of the present study was to investigate root traits in terms of root morphological, anatomical, and mycorrhizal features of a terrestrial orchid, Peristylus goodyeroides in relation to an ecological significance of root traits in survival of seedlings, juveniles, and adults of the orchid. Results showed that some morphological characters (root length and depth), anatomical features (cortical cell size, xylem number and diameter), and mycorrhizal features (peloton size and number) were significantly different between seedlings, juveniles, and adults. In relation to root functional traits, lowest root length, depth, xylem number and diameter, peloton size and number in seedlings can be associated with low capacity in water and nutrient acquisition that might explain low survival of seedlings relative to juveniles and adults. Present study has implication for orchid conservation suggesting high attention in low survival rate of seedlings related to specificity in some of their morphological, anatomical, and mycorrhizal features which can be associated with low capacity in water and nutrient acquisition. It is vital to ensure water availability for seedlings, particularly, during dry seasons to decrease high mortality of seedlings as such high mortality can have adverse impacts on long-term survival of the orchid population.

Modified Humic Substances as Soil Conditioners: Laboratory and Field Trials

The paper is devoted to the development and performance testing of a soil conditioner based on leonardite humic substances (LHS) modified with 3-aminopropyltriethoxysilane (APTES). The modified HS were obtained by adding APTES to LHS solution at different mass ratios of LHS and APTES, followed by the investigation of siloxane structures using 31Si NMR spectroscopy. The Urbic Technosol was used as a model soil. The size and amount of water-stable soil aggregates were estimated using wet sieving and laser diffraction, respectively. Toxicity was evaluated by monitoring microbial substrate-induced respiration (SIR) and seedling bioassay. Laboratory column experiments demonstrated an increase in water-stability of the 3–5 mm soil aggregates after LHS-APTES application. Field tests showed an increase in the average weighted diameter of micro aggregates (from 59 to 73 μm) and water-stable macroaggregates (from 1.6 to 2.9 mm) due to the LHS-APTES amendment. A substantial increase in SIR from 5 to 9 mg CO2 (kg h)−1 was detected. Better survival of seedlings was observed. The obtained beneficial results indicate that APTES-modified HS can be successfully used as a soil conditioner. The formation of extended siloxane networks was suggested as the main mechanism of the observed improvement in the structure of the amended soils.

The effect of cadaverine on redox homeostasis of wheat seedling roots and their resistance to damage heating

Polyamines are plant metabolites involved in many processes under physiologically normal and stressful conditions. Cadaverine is one of the least studied plant polyamines. The relationship between its physiological effects and the formation of signaling mediators, in particular, reactive oxygen species (ROS), has hardly been specially studied. The aim of this work was to study the possible protective effect of cadaverine on wheat (Triticum aestivum L.) seedlings under heat stress and its relationship with the formation and detoxification of ROS by antioxidant enzymes. Etiolated seedlings of soft winter wheat variety Doskonala were used in the work. We treated three-day-old seedlings with cadaverine at concentrations ranging from 0.05 to 2.5 mM by adding it to the root incubation medium. In some variants of the experiment, we treated seedlings with a hydrogen peroxide scavenger dimethylthiourea (DMTU - 150 μM), a diamine oxidase inhibitor aminogunidine (1 mM) or an inhibitor NADPH oxidase imidazole (10 μM), as well as the indicated inhibitors in combination with cadaverine. The hydrogen peroxide content and the activity of antioxidant enzymes were determined in the roots of seedlings a certain time after treatment with the studied compounds. One day after the treatment of seedlings with cadaverine, ROS antagonists, and a combination of effectors, the seedlings were subjected to damaging heating in a water thermostat (10 min at 45 °C). 24 h after heating, we assessed the content of the products of lipid peroxidation (LPO) in the roots and, after 3 days, the survival of seedlings. Incubation in the presence of cadaverine increased the resistance of seedlings to damaging heat (See Fig. 1). The highest relative number of surviving seedlings was observed in the variant with 1 mM cadaverine treatment. Under the effect of cadaverine, the content of hydrogen peroxide in the roots increased (See Fig. 2). We observed a noticeable effect 1-4 h after the start of treatment, with a maximum after 2 h. Treatment of seedlings with a scavenger of hydrogen peroxide DMTU removed the manifestation of the effect of an increase in the content of H2 O2 in the roots caused by the action of cadaverine (See Fig. 3). This effect was also completely eliminated by the diamine oxidase inhibitor aminoguanidine and was almost unchanged in the presence of the NADPH oxidase inhibitor imidazole. The effect of heat stress on seedlings caused an increase in the content of the LPO products in them. Treatment with cadaverine markedly reduced this manifestation of oxidative stress. The antioxidant DMTU and the diamine oxidase inhibitor aminoguanidine largely neutralized the protective effect of cadaverine (See Fig. 4a). At the same time, the NADPH oxidase inhibitor imidazole had almost no effect on the manifestation of the effect of cadaverine on the LPO products content in roots. Under the influence of DMTU and aminoguanidine, but not imidazole, the positive effect of cadaverine on the survival of seedlings after damaging heating was also leveled out (See Fig. 4b). The treatment of seedlings with cadaverine caused a change in the activity of antioxidant enzymes in the roots (superoxide dismutase - SOD, catalase, and guaiacol peroxidase) (See Fig. 5). DMTU and aminoguanidine neutralized the effect of cadaverine-induced increase in the activity of catalase and guaiacol peroxidase, but had almost no effect on the increase in SOD activity in roots induced by this diamine (See Fig. 6). The NADPH oxidase inhibitor imidazole did not significantly affect the manifestation of the effect of increasing the activity of antioxidant enzymes when seedlings are treated with cadaverine. We can conclude that one of the signaling mediators involved in the regulation activity of catalase and guaiacol peroxidase and in the induction of heat resistance of wheat seedlings by exogenous cadaverine is hydrogen peroxide, which is formed during the oxidation of cadaverine by diamine oxidase. At the same time, the modification of SOD activity in the roots of wheat seedlings with cadaverine, apparently, can occur without the participation of ROS.

NMR-Based Metabolomic Analysis and Microbial Composition of Soil Supporting Burkea africana Growth

Burkea africana is a leguminous tree used for medicinal purposes, growing in clusters, on soils impoverished from most nutrients. The study aimed to determine the factors responsible for successful reproduction and establishment of the B. africana trees in nature, as all efforts for commercial production has been proven unsuccessful. An investigation was carried out to determine the metabolomic profile, chemical composition, and microbial composition of the soils where B. africana grows (Burkea soil) versus the soil where it does not grow (non-Burkea soil). 1H-NMR metabolomic analysis showed different metabolites in the respective soils. Trehalose and betaine, as well as a choline-like and carnitine-like compound, were found to be in higher concentration in Burkea soils, whereas, acetate, lactate, and formate were concentrated in non-Burkea soils. Liquid Chromatography-Mass Spectrometry analysis revealed the presence of numerous amino acids such as aspartic acid and glutamine to be higher in Burkea soils. Since it was previously suggested that the soil microbial diversity is the major driver for establishment and survival of seedlings in nature, Deoxyribonucleic acid (DNA) was extracted and a BLAST analysis conducted for species identification. Penicillium species was found to be highly prevalent and discriminant between the two soils, associated with the Burkea soils. No differences in the bacterial composition of Burkea and non-Burkea soils were observed. The variances in fungal composition suggests that species supremacy play a role in development of B. africana trees and is responsible for creating a supporting environment for natural establishment and survival of seedlings.

Evaluation of Eucalyptus Clones Under Seasonal Waterlogging Conditions in South-Western Punjab

Eucalyptus is widely planted genus in many continents due to its rapid growth, several uses and good adaptability to climates and soil types. This study was based on nine Eucalyptus clones/progenies (C-413, C-3020, C-2135, C-7, C-2045, C-411, C-526, C-316 and seedlings) planted at farmers field experiencing seasonal waterlogging. The experiment was planted following randomized block design with plot size of 12 trees replicated four times. The survival of Seedlings, C-7, C-413, C-526 and C-316 was better and varied from 78.3 to 88.3 percent. Significant differences were found for tree height and diameter at age of 2 and 4 year, and volume index at age of 4 year. The tree height and diameter at breast height at 4 year age varied from 5.93 to 6.76 m and 56.4 to 87.6 mm, respectively. The relative ranking on basis of volume index was C-413>C-316>C-411>C-7>C-526. Clones C-413, C-316, C-7 and C-526 were promising based on adaptability and growth traits.

Survival and initial growth in the field of eucalyptus seedlings produced in different substrates

The objective of this work was to evaluate the survival and initial growth, in the field, of eucalyptus seedlings produced in different substrates. Eucalyptus benthamii seedlings produced in 36 substrates were evaluated in the field. The substrates consisted of mixtures, at different volumetric proportions, of: carbonized rice husk, charcoal with granulometry between 1.0-3.0 mm, charcoal with granulometry between 3.0-5.0 mm, coconut fiber, semi-decomposed pine bark, fine vermiculite, sewage sludge, and peat moss. At 1, 2, 3, 6, 12, 18, and 24 months after planting, survival, height, and diameter were determined. At 24 months after planting, height increment, diameter increment, transversal area, and basal area were also measured. The seedlings that showed 100% survival after 24 months under field conditions were those grown in the nursery in substrates with a higher proportion of fine vermiculite, sewage sludge, and peat moss, that is, in substrates with a higher microporosity. However, there is no effect of substrate characteristics on seedling initial growth in the field. A significant correlation is observed between the survival of seedlings at 6 months and their diameter at the end of the nursery period, evidencing the importance of this characteristic for the establishment of the plant in the field, regardless of the used substrate.

Native generalist consumers interact strongly with seeds of the invasive wild cucumber (Echinocystis lobata)

When alien plant species arrive in a new environment, they develop novel interactions with native biota that can range from negative to positive. Determining the nature and strength of these interactions is integral to understanding why some aliens are suppressed and others become highly invasive pests. For introduced terrestrial plants, seed and seedling interactions with native biota are crucial, because most nascent populations start from seed. Herein, we explored interactions between native generalist rodent and bird consumers and seeds of the invasive wild cucumber Echinocystis lobata by conducting seed-offering experiments in Poland. We also evaluated how interspecific competition from native plants and intraspecific competition from clustering of E. lobata seed (clustering resembling consumer seed caching) affected survival of seedlings and young plants. Native consumers interacted strongly with E. lobata seeds, with rodents removing 98% of seeds from ground locations and birds removing 24% of elevated seeds. Camera and live traps indicated that striped field mice Apodemus agrarius were the predominant rodent removing seeds. Camera traps and visual observations indicated that great tits Parus major and European jays Garrulus glandarius were the primary bird species removing elevated seeds. While some level of seed removal was likely attributable to seed predation, as indicated by seed coat remains, we also observed evidence that rodents may cache E. lobata seeds and Garrulus glandarius are known to cache and disperse seeds. Monitoring of seedlings indicated that increasing cover of native plants and clustering of E. lobata seedlings both reduced survival of seedlings and young plants due to inter- and intraspecific competition, respectively. Hence, caching by generalist consumers may disperse E. lobata seeds, which are heavy and lack dispersal adaptations, but such caching may also reduce individual seedling survival rates. Fully understanding invasion success of the E. lobata will require evaluating the net effects of generalist consumers on its recruitment and dispersal.

The influence of organic plant material on seed germination and development of Scots pine Pinus sylvestris L. seedlings

In this article we analysed the influence of plant-based organic admixtures on the germination process of seeds and the early development of Scots pine Pinus sylvestris L. seedlings. The intensity of dumpin-off diseases within the culture was recorded after applying each of the admixtures. Organic material of nettle Urtica dioica L., softwood litter, hardwood litter and peat were applied to the nursery substrate in two ways, either as an admixture in crushed form or in granulated form. None of the introduced admixtures influenced the germination of seeds or the survival rate of pine seedlings positively. The best results were obtained with a substrate without admixtures used as a control, which is the most common nursery substrate. The worst seed germination rate was observed on the substrate enriched with the organic material from nettles. In pots with granulated organic material from hardwood litter, significantly more seedlings showed signs of post-emergence dermatitis. In all other cases, there was no clear difference between the crushed or granulated admixture in either germination or survival of seedlings. We furthermore demonstrated that the process of granulating plant material leads to an approximately 10-fold increase in the bulk density of the granulated substance, which translates directly into volume reduction.

Resource Allocation, Pit Quality, and Early Survival of Seedlings Following Two Motor-Manual Pit-Drilling Options

Afforestation and reforestation operations constitute an important part of the forest management, being crucial for the sustainability of forests. In such operations, there are three options to prepare the planting holes: manual, partly mechanized, and fully mechanized. Given the high cost of mechanized planting and the ergonomic issues of manual planting, one option which is worth exploring is using of augers, because they have the potential to mitigate and/or eliminate intense physical effort and aspects of some of the ergonomic problems. This study examines the early survival of seedlings following the use of augers to prepare the planting pits. Working time, fuel consumption and physical quality of the pits were evaluated on nine sites for two drill types differentiated by their diameter (150 vs. 200 mm). Time consumption was systematically higher when using the larger drill, while fuel consumption was not found to be statistically different. The larger drill systematically produced pits characterized by less physical quality in terms of resistance to penetration and shear strength, but the early survival of seedlings was higher when using this drill size. Survival probability modeled by means of logistic regression showed that pit size was among the factors that may affect the early survival of seedlings. The study concludes that the larger drill would be more appropriate to plant seedlings, but further studies should be arranged to see if long-term survival would be affected in this case.