Root Substrate Research Articles

Comparison of the efficiency of synthetic auxins and biostimulants and two types of substrate in rooting of shoot cuttings in ‘Pi-ku 1’ rootstock

The low-cost propagation of semi-dwarf cherry rootstock is an essential issue in the production of maiden trees of this species. Among the promising rootstocks is ‘Pi-ku 1’, obtained in Germany. However, the possibility of its propagation using shoot cuttings has not been investigated. It was the purpose of this study. Two ways of cuttings treatment before placing them in the substrate were assessed. One used two preparations in powder (Rhizopon AA and Ukorzeniacz AB), and the second used two alcoholic auxin solutions (IAA and IBA). Instead of synthetic auxins, foliar spraying with two biostimulants was performed (Goteo and Bispeed). All the applied treatments increased the rooting percentage of ‘Pi-ku 1’ rootstock cuttings compared to the control from 5% for Rhizopon AA to 18.2% for auxin IBA. The exception was the lack of a positive effect of the Bispeed biostimulant (less than 5.2%). The use of synthetic auxins increased the number of utting roots more than three times (IBA) or almost twice (Ukorzeniacz AB) and their length more than twofold (IAA, Rhizopon AA) in proportion to the control. The effect of synthetic auxin treatments on the remaining growth parameters under study was also positive. Foliar treatment of cuttings with biostimulants did not change their growth. Only in one of the two years of the study did the fresh mass of cuttings improve after using Goteo biostimulant (7.5%). As part of the experiment, the effect of two substrate types – peat mixed with perlite and peat with sand – was also tested. During the two years of research, the cuttings were rooted several percent better in peat and sand (2.7% – 2018 and 4.4% – 2019). Using peat with sand as a rooting substrate significantly improved the number and length of roots (11.90 and 125.10) of Pi-ku 1 rootstock cuttings compared to the second one (9.23 and 109.08, respectively). All treatments applied to cuttings, except two biostimulants, increased the amount of chlorophyll in the leaves.

Distinct orchid mycorrhizal fungal communities among co-occurring Vanilla species in Costa Rica: root substrate and population-based segregation.

Despite being the second largest family of flowering plants, orchids represent community structure variation in plant-microbial associations, contributes to niche partitioning in metacommunity assemblages. Yet, mycorrhizal communities and interactions remain unknown for orchids that are highly specialized or even obligated in their associations with their mycorrhizal partners. In this study, we sought to compare orchid mycorrhizal fungal (OMF) communities of three co-occurring hemiepiphytic Vanilla species (V. hartii, V. pompona, and V. trigonocarpa) in tropical forests of Costa Rica by addressing the identity of their OMF communities across species, root types, and populations, using high-throughput sequencing. Sequencing the nuclear ribosomal internal transcribed spacer (nrITS) yielded 299 fungal Operational Taxonomic Units (OTUs) from 193 root samples. We showed distinct segregation in the putative OMF (pOMF) communities of the three coexisting Vanilla hosts. We also found that mycorrhizal communities associated with the rare V. hartii varied among populations. Furthermore, we identified Tulasnellaceae and Ceratobasidiaceae as dominant pOMF families in terrestrial roots of the three Vanilla species. In contrast, the epiphytic roots were mainly dominated by OTUs belonging to the Atractiellales and Serendipitaceae. Furthermore, the pOMF communities differed significantly across populations of the widespread V. trigonocarpa and showed patterns of distance decay in similarity. This is the first report of different pOMF communities detected in roots of wild co-occurring Vanilla species using high-throughput sequencing, which provides evidence that three coexisting Vanilla species and their root types exhibited pOMF niche partitioning, and that the rare and widespread Vanilla hosts displayed diverse mycorrhizal preferences.

Modeling the Mechanical Properties of Root–Substrate Interaction with a Transplanter Using Artificial Neural Networks

The mechanical properties of a plug seedling substrate determine whether it will crush during the transplantation, thereby affecting the integrity of the root system and the survival rate of transplanted seedlings. In this study, we measured eight morphological parameters of pepper seedlings using machine vision and physical methods, and the corresponding substrate mechanical parameters of the plug seedlings were tested using a texture analyzer. Based on the experimental data, a BPNN framework was constructed to predict the substrate mechanical properties of plug seedlings at different growth stages. The results indicate that the BPNN with a framework of [8, 15, 15, 1] exhibits higher R2 and lower errors. The mean absolute error (MAE), mean squared error (MSE), and mean absolute percentage error (MAPE) values are 7.669, 88.842, and 9.076%, respectively, with an R2 of 0.867. The average prediction accuracy of 20 test data set is 90.472%. Finally, predictions and experimental validations were conducted on the substrate mechanical properties of seedlings grown for 47 days. The results revealed that the BPNN achieved an average prediction accuracy of 93.282%. Additionally, it exhibited faster speed and lower computational costs. This study provides a reference for the non-intrusive estimation of substrate mechanical properties in plug seedlings and the design and optimization of transplanting an end-effector.

Fine root decomposition in forest ecosystems: an ecological perspective.

Fine root decomposition is a physio-biochemical activity that is critical to the global carbon cycle (C) in forest ecosystems. It is crucial to investigate the mechanisms and factors that control fine root decomposition in forest ecosystems to understand their system-level carbon balance. This process can be influenced by several abiotic (e.g., mean annual temperature, mean annual precipitation, site elevation, stand age, salinity, soil pH) and biotic (e.g., microorganism, substrate quality) variables. Comparing decomposition rates within sites reveals positive impacts of nitrogen and phosphorus concentrations and negative effects of lignin concentration. Nevertheless, estimating the actual fine root breakdown is difficult due to inadequate methods, anthropogenic activities, and the impact of climate change. Herein, we propose that how fine root substrate and soil physiochemical characteristics interact with soil microorganisms to influence fine root decomposition. This review summarized the elements that influence this process, as well as the research methods used to investigate it. There is also need to study the influence of annual and seasonal changes affecting fine root decomposition. This cumulative evidence will provide information on temporal and spatial dynamics of forest ecosystems, and will determine how logging and reforestation affect fine root decomposition.

Leaf yield and mineral content of mizuna in response to cut-and-come-again harvest, substrate particle size, and fertilizer formulation in a simulated spaceflight environment

The Veggie plant-growth unit deployed onboard the International Space Station (ISS) grows leafy vegetables to supplement crew diets. “Cut-and-come-again” harvests are tested to maximize vegetative yield while minimizing crew time. Water, oxygen, and fertilizer delivery to roots of leafy greens growing in microgravity have become the center of attention for Veggie. Current Veggie technology wicks water into particulate root substrates incorporating controlled-release fertilizer (CRF). Mizuna mustard (Brassica rapa) was grown under ISS-like environments in ground-based Veggie-analogue units comparing crop response to combinations of two different substrate particle sizes, two different fertilizer formulations, and three leaf-harvest times from each plant. Fine-particle porous ceramic substrate (Profile©) was compared with a 40:60 mix of fine-particle porous ceramic Profile© + coarse porous ceramic Turface© substrate. Identical 18-6-8 (NPK) CRF formulations consisting of [50% fast-release (T70) + 50% intermediate-release (T100) prills] vs. [50% fast-release (T70) + 50% slow-release (T180) prills] were incorporated into each substrate, and leaf tissues were harvested from each treatment combination at 28, 48, and 56 days after sowing. The combination of T100 CRF in 100% Profile© substrate gave the highest fresh mass (FM) and leaf area (LA) across harvests, whereas T180 CRF in 40% Profile© gave the lowest. Dry-mass (DM) yields varied with effects on leaf area. Tissue nitrogen (N) and potassium (K) specific contents declined across harvests for all treatment combinations but tended to be highest for T100 CRF/100% Profile©, and lowest for T180 CRF/40% Profile©. These major macronutrients were taken up faster by roots growing in small particle-size substrate incorporating intermediate-rate CRF, but also were depleted faster from the same treatment combination, suggesting it may not continue to be the best combination for additional harvests. Micronutrients did not decline in tissue specific content across treatment combinations, but manganese (Mn) accumulated in leaf tissue across treatments and apparently comes mainly from the ceramic substrate, regardless of particle size. Substrate leachate analysis following final harvest indicated that pH remained in the range for nominal availability of mineral nutrients for root uptake, but electro-conductivity measurements suggested depletion of fertilizer salts from root zones, especially from the treatment combination supporting the highest yields and major macronutrient contents. Although 100% Profile© was the better growth substrate for mizuna in combination with intermediate-rate CRF and three cut-and-come-again harvests in ground-based studies, mixed-particle-size substrates may be a better choice for plant growth under microgravity conditions, where capillary forces predominant and tend to cause saturation of a fine medium with water. Since there were no statistically significant interactions between substrate and fertilizer in this study, our ground-based findings for CRF choice should translate to the best substrate choice for microgravity, but if NASA wants to consider additional cut-and-come-again harvests from the same mizuna plants, more complex CRF formulations likely will have to be investigated.

Manganese indicates root decomposition rates across soil layer, root order, and tree species: Evidence from a subtropical forest

Different spatial locations provide different external conditions for root decomposition, while species and root order cause obvious differences in root substrate quality. Both differences in internal and external conditions may determine root decomposition rate. We explored the effects of decomposition position, root order, and species differences on root decomposition, and determined the role of manganese (Mn) in root decomposition. We conducted a fine root decomposition experiment using roots from Schima superba, Cleyera japonica, and Eurya loquaiana (separated into orders 1−3, 4−5, and 6) in the litter layer, and at 0−10 cm, 20−30 cm, and 40−50 cm soil depth in a subtropical forest. Root mass and concentration of C, N, P, Mn, condensed tannins and total phenolics were measured during two years of decomposition. Root decomposition rates decreased with increasing soil depth for all root samples. Compared to decomposition at 0−10 cm soil depth, remaining mass (% of initial) declined by 7%–34% in the litter layer and increased by 17%–37% at 40−50 cm soil depth. Lower-order roots had a higher decomposition rate than higher-order roots in the litter layer, but at 40−50 cm soil depth, we observed the opposite. Root litter Mn concentration and remaining mass were negatively correlated during the whole decomposition period including the early, middle, and late stages. Initial root Mn content was negatively correlated with remaining mass after two years of decomposition in the litter layer, and at 20−30 cm, 40−50 cm soil depth. However, no significant relationship between mass remaining and initial root N, P, condensed tannins and total phenolics were observed in the subsoil. Variance partitioning showed that the soil layer contributes significantly to the variance in remaining root mass, C, and Mn, whereas root order group contributed more than the soil layer to remaining root N and P. Our results indicate that soil depth is more important than root order for fine root decomposition rate at a site scale. Relative root decomposition rate between lower- and higher-order roots depends on the decomposition environment. Overall, this study strongly suggests that root Mn concentration (whether in initial or other decomposition stages) was much more consistently correlated with mass remaining than traditional predictors of N, P, condensed tannins, or total phenolics. Root Mn concentration greatly indicates root decomposition rates across soil layers, root orders, and species. Initial root Mn concentration and Mn supply capacity of the decomposition environment jointly control root decomposition rates throughout the decomposition process.

Effects of Exogenously Applied Copper in Tomato Plants’ Oxidative and Nitrogen Metabolisms under Organic Farming Conditions

Currently, copper is approved as an active substance among plant protection products and is considered effective against more than 50 different diseases in different crops, conventional and organic. Tomato has been cultivated for centuries, but many fungal diseases still affect it, making it necessary to control them through antifungal agents, such as copper, making it the primary form of fungal control in organic farming systems (OFS). The objective of this work was to determine whether exogenous copper applications can affect AOX mechanisms and nitrogen use efficiency in tomato plant grown in OFS. For this purpose, plants were sprayed with ‘Bordeaux’ mixture (SP). In addition, two sets of plants were each treated with 8 mg/L copper in the root substrate (S). Subsequently, one of these groups was also sprayed with a solution of ‘Bordeaux’ mixture (SSP). Leaves and roots were used to determine NR, GS and GDH activities, as well as proline, H2O2 and AsA levels. The data gathered show that even small amounts of copper in the rhizosphere and copper spraying can lead to stress responses in tomato, with increases in total ascorbate of up to 70% and a decrease in GS activity down to 49%, suggesting that excess copper application could be potentially harmful in horticultural production by OFS.

Root hypoxia aggravates the effects of saline tailings water on the growth and physiology of woody plants

AimsOil sands mining in the boreal forest produces large volumes of liquid tailings. Forestry research has generally focused on the thickness and composition of the soil layers to be placed on top of the tailings during reclamation. However, tailings release water, which may seep into the root zone and affect plants. Furthermore, the interactions and combined effects of root hypoxia and root substrate chemistry on plant responses are poorly understood.MethodsThe effects of the aqueous phase of novel tailings (Non-Segregating Tailings—NST) were studied under well-aerated and hypoxic conditions in three relatively waterlogging tolerant tree species [tamarack (Larix laricina), black spruce (Picea mariana), and balsam poplar (Populus balsamifera)] and three relatively sensitive tree species [lodgepole pine (Pinus contorta), jack pine (Pinus banksiana), and aspen (Populus tremuloides)] by growing them in hydroponic solutions in a controlled environment.ResultsRoot hypoxic conditions further reduced the survival, growth, and physiology of plants exposed to NST. Our results confirm that NST water produces the same deleterious effects in plants as previously reported in the amalgamated oil sands tailings. Root hypoxia inhibited salt sequestration in trembling aspen and may have inhibited an osmoregulative mechanism in black spruce needles.ConclusionsOur results highlight the potential impact of water seepage from buried tailings on reclamation success. Furthermore, hypoxic conditions can aggravate these effects by inhibiting salt stress mechanisms. We suggest that the preparation of reclamation sites impacted by tailings water should involve efforts to enhance soil aeration to minimize the detrimental effects on plants.

Potential Use of Cardunculus Biomass on Pleurotus eryngii Production: Heteroglycans Content and Nutritional Properties (Preliminary Results)

The new perspective of using waste biomass to cultivate mushrooms as a source of protein for human nutrition, in line with the circular economy principles, is receiving increasing attention in the scientific community and represents great wealth in terms of environmental sustainability. Pleurotus eryngii is a mushroom also known as cardunculus mushroom due to its ability to grow on this plant. This study explores the potential intrinsic properties of cardunculus (for example, the presence of inulin in the roots) as raw material for the growth of cardunculus mushrooms, and the influence on heteroglycan content and nutrition parameters of the fruiting bodies. Both mycelium and fruiting bodies were used to determine the heteroglycan content in the presence of inulin or cardunculus roots rich in inulin. To produce heteroglycans from P. eryngii in greater quantities and shorter times without having to wait for the formation of the fruiting bodies, the mycelium could be used. The results showed that the presence of cardunculus biomass positively influences the heteroglycan content of P. eryngii. In terms of nutritional parameters, higher contents of polyphenols, flavonoids, anthocyanins, and antioxidant activity were detected in P. eryngii grown on the cardunculus stem and root substrate. In conclusion, recycling cardunculus biomass to generate growth blocks for edible mushrooms is a winning choice due to the opportunity to use this biomass waste, which is gaining more and more attention due to the increase in cultivated areas and the use of fruiting bodies of P. eryngii as a functional food and source of molecules with potential biological activities.

Contrasting patterns of nitrogen release from fine roots and leaves driven by microbial communities during decomposition

Leachate from decaying root and leaf litter plays crucial roles in soil biogeochemical processes in forest ecosystems. Unlike for leaf litter, however, the chemical composition and microbial community of root litter leachate are poorly understood. We hypothesized that both leachate nitrogen (N) composition and microbial communities differ between plant organs and decomposition stages and that leachate composition affects microbial community composition. We conducted a 2.5-year laboratory incubation using root and leaf substrate from Cryptomeria japonica and Chamaecyparis obtusa. We monitored the N forms released and used metabarcoding to characterize the microbial communities. Leachate N accounted for 40 % and 30 % of net N losses from C. japonica and C. obtusa roots, respectively; the remainder was probably lost in gaseous forms. In contrast, leaves absorbed N during the incubation regardless of tree species. The predominant N form in root leachate was nitrate (NO3−); cumulative NO3− quantity was 22.6 and 25.5 times greater in root than in leaf leachate for C. japonica and C. obtusa, respectively. A nitrifying bacterium was selected as the indicator taxon in root substrates, whereas many families of N-fixing bacteria were selected in leaf substrates. At the end of the incubation period, bacterial taxonomic diversity was high in both organs from both tree species, ranging from 177 to 339 taxa and increasing with time. However, fungal diversity was low for both organs (72 to 155 taxa). Shifts in bacterial community structure were related to NO3− concentration and leachate pH, whereas shifts in fungal community structure were related to leachate pH. These results suggest that the contrasting N dynamics of root and leaf substrates are strongly affected by the characteristics of and the microbes recruited by their leachates. Understanding organ-specific litter N dynamics is indispensable for predicting N cycling for optimal management of forest ecosystems in a changing world.

Biochar granulation, particle size, and vegetation effects on leachate water quality from a green roof substrate.

Biochar, due to its favourable physiochemical properties, has been promoted as an ideal substrate additive on green roofs, with potential benefits to hydrological function. However, biochar is susceptible to water erosion, which may result in biochar loss and water pollution. The use of granulated biochars or biochars in large particle sizes could potentially alleviate biochar erosion loss, but effects on leachate quality have not been investigated. Also, biochar type and particle size influence plant performance, and effects on discharge quality may vary with vegetation. We assessed the effects of unprocessed and granulated biochars at five (0.25-0.5mm, 0.5-1mm, 1-2mm, 2-2.8mm, 2.8-4mm) and four (1-2mm, 2-2.8mm, 2.8-4mm, and 4-6.3mm) particle size ranges, respectively, on leachate quality on a typical green roof substrate, with presence and absence of vegetation (Agastache foeniculum - a drought-tolerant native forb). We evaluated integrated leachate quality using the CCME Water Quality Index (WQI). Unprocessed biochars reduced nutrient leaching due to increased water retention capacity (WRC) and total porosity. In contrast, granulated biochars, although showing less pronounced mitigation of nutrient leaching, reduced total suspended solids (TSS) and improved WQI in leachate due to enhanced plant performance. In addition, small biochar particles better reduced nutrient leaching and particle loss than large biochar particles, possibly due to increased WRC and formation of water-stable aggregates. The presence of vegetation generally reduced the leaching of nutrients and TSS, consistent with plant nutrient uptake and root substrate stabilization. However, plant biomass was correlated with increased total N leaching, likely due to litter inputs and rapid litter decomposition. We conclude that applications of granulated biochars may best improve discharge quality from green roofs through sorption effects and by enhancing plant performance.

Secondary metabolite changes in Maymars juniper cuttings (Juniperus sabina) under different treatments of propagation (IBA, substrate and harvest time of cutting)

The Endemic Juniper of Maymars (Juniperus sabina) is one of the most valuable plants in forested areas. The objectives of this experiment were: I) to determine the best conditions for stem cutting propagation of this species, and II) to examine changes in some of the secondary metabolites during the four months (the first of each season): January, April, July, and October, after rooting of cuttings. The research was done with the treatment of five levels of Indole Butyric Acid, including: 0, 1000, 2000, 4000, and 8000 ppm in four rooting substrates, including perlite, perlite-cocopeat (1:1), pumice, and a mixed rooting substrate (sand, perlite, cocopeat, vermicompost, and potash; 1:1:1:1:1) in the four seasons of the year, with stem cuttings having an average length of 15 cm. The best treatment with more than 50% rooting was seen in April at levels of 4000 and 1000 ppm, and the best substrate was perlite cocopeat. Using lower levels of IBA led to a reduction in total phenol content in the cuttings during the rooting period. The flavonoid content of the cuttings varied across different seasons. Based on these results, we recommend this way of propagation for Juniperus sabina production. This propagation method takes less time in comparison with sexual propagation from seed.

Effects of New Compounds into Substrates on Seedling Qualities for Efficient Transplanting

Automating vegetable seedling transplanting has led to labor-saving opportunities and improved productivity. Some changes in seedling agronomy are necessary for efficient transplanting. In this study, the local nursery substrates were added with the herbaceous peat, the sphagnum peat, and the coir peat, respectively. Effects of the new compound substrates were investigated on the seedling growth qualities and the root substrate strength. In the results, we found that the addition of three compound mediums significantly affected the physiochemical properties of the original substrates. Under the same conditions of cultivating seedlings, appropriate additions of new compounds promoted the seedling growth. Moreover, deficient or excessive additions inhibited the growing development of seedlings and their roots. The corresponding additions also improved the structural characteristics of the root lumps. Compared with the two other compounds, the nursery substrates added with the sphagnum peat were optimized in contribution to the seedling qualities and the root substrate strengths. As the local substrate and the sphagnum peat were mixed at a volume ratio of 2:1, the dry matter accumulation of seedlings was 2.18 times more than the original. Their root lumps had the best consolidation strength. This new compound of substrates may be an effective application for the necessary qualities of seedlings for automatic transplanting.

Early production of strawberry in aquaponic systems using commercial hydroponic bands

Aquaponics is emerging as an interesting alternative for sustainable agriculture which meets the philosophy of circular economy, decreasing not only the need of external resources but also increasing their use efficiency. Several studies can be found dealing with the analysis of different fish species combined with a great variety of crops in systems with diverse sophistication levels. Strawberry crop may be interesting for aquaponics systems. However, early production and the quality of the fruit, which are crucial factors affecting crop profitability, have not been previously assessed in aquaponics systems. This work aimed at evaluating these factors together with the consumption of resources in strawberry production using commercial multi-layer NFT channels coupled with tench production in an aquaponic system. Production of tench with low density of fish (700–1300 g m−3) was associated to 2 hydroponic lines where plants were transplanted in rockwool plugs or bare roots. Despite the fact that the transplanting of the strawberries was performed one month later than usual for this crop, the extra-early production was 31.9 and 33.6 g per plant for rockwool and bare root substrates, respectively. No significant differences were found neither in strawberry production nor in fruit quality for the two types of substrates studied. However, parameters related to earliness varied differently along time between bare root and rockwool. The cultivation of bare root plants is recommended, since it involves lower costs by saving in the acquisition of the substrate and less environmental and health problems for workers. Despite the fact that tench is a species very well adapted to the weather conditions in the production area, its low average daily gain ratios and its long growth cycle makes it unsuitable for combination with the cultivation of strawberry. However, the combination of a joint production of fish and plants in simple aquaponic systems would allow savings in fertilizer and water, within a production framework of circular economy.

Comparison of two controlled-release fertilizer formulations for cut-and-come-again harvest yield and mineral content of Lactuca sativa L. cv. Outredgeous grown under International Space Station environmental conditions

Red Romaine leaf lettuce (Lactuca sativa L. cv. Outredgeous) was grown in ground-based analogues of the Veggie plant-growth units used to grow salad vegetables for astronauts on the International Space Station (ISS). Plants were grown for 56 days with three “cut-and-come again” leaf harvests from the same plants. Six Biomass-Production-Systems-for-Education (BPSe) units were used to grow ‘Outredgeous’ (‘OR’) lettuce in a walk-in growth chamber under temperature, humidity, and LED-lighting conditions similar to those occurring in Veggie on ISS. Because of the ISS micro-gravity environment, both Veggie and ground-based BPSe units utilize one-way capillary wicking of water into an arcillite clay root substrate. In the present study, two different controlled-release fertilizer (CRF) formulations incorporated into the arcillite were compared for effects on ‘OR’ growth rate, overall yield, and mineral content of leaves harvested from the same plants 28, 48, and 56 days after planting. Both CRF treatments had a rapid-releasing T70 component that kept growth rate equivalent over the first two harvests. Growth rate for both CRF treatments increased from the first to the second harvest, but then declined from the second to the third harvest, more so for the slower-releasing T180 CRF than for the moderately-releasing T100 CRF. Tissue content of the macro-nutrients N, P, and K declined at each harvest for both CRFs, while content of the micro-nutrients B, Zn, and Mn increased. Although pH did not go out of the nominal range for availability of mineral nutrients to roots over the cropping cycle, and electrical-conductivity of rootzone salts was neither excessive nor depleted, tissue macronutrient depletion and micro-nutrient accumulation may have contributed to yield declines. Although either CRF formulation can support adequate yield of ‘OR’ lettuce over a 56-day period, the moderately-releasing T100 formulation tends to give slightly higher yield, especially during the last growth increment, and with non-deficient mineral content.

Phi thickenings in Brassica oleracea roots are induced by osmotic stress and mechanical effects, both involving jasmonic acid.

Phi thickenings are peculiar secondary cell wall thickenings found in radial walls of cortical cells in plant roots. However, while thickenings are widespread in the plant kingdom, research into their development has been lacking. Here, we describe a simple system for rapid induction of phi thickenings in primary roots of Brassica. Four-day-old seedlings were transferred from control agar plates to new plates containing increased levels of osmotica. Phi thickening development occurred within a narrow region of the differentiation zone proportional to osmolarity, with cellulose deposition and lignification starting after 12h and 15h, respectively. However, osmoprotectants not only failed to induce phi thickenings, but inhibited induction when tested in combination with thickening-inducing osmotica. An independent, biomechanical pathway exists regulating phi thickening induction, with root growth rates and substrate texture being important factors in determining thickening induction. Phi thickening development is also controlled by stress-related plant hormones, most notably jasmonic acid, but also abscisic acid. Our research not only provides the first understanding of the developmental pathways controlling phi thickening induction, but also provides tools with which the functions of these enigmatic structures might be clarified.

Millicompost: Sustainable substrate for the production of dragon fruit seedlings (Selenicereus undatus)

The success of the production of dragon fruit seedlings propagated vegetatively depends on several factors, such as the appropriate choice of the substrate for rooting. It has been verified that the millicompost has contributed to the production of seedlings of some species, however, there are no reports for the dragon fruit. Thus, the objective was to evaluate the efficiency of the millicompost generated by the activity of the diplopods Trigoniulus corallinus in the cuttings of the red dragon fruit. The substrates used were: S1) millicompost, S2) sand + bovine manure and S3) Biomix®. Characterizations of the physical-chemical, chemical, and physical properties of the substrates were carried out. The phytotechnical parameters evaluated in the cuttings of dragon fruit were: number of shoots, length of the largest shoot, fresh and dry masses of the shoot and roots. The millicompost had physicochemical, chemical, and physical properties, promoting greater development of dragon fruit, whose levels of nutrients and physical characteristics, in addition to being superior to the other substrates, were able to provide seedlings of higher quality and size compared to seedlings from the other two substrates tested. The millicompost represents an alternative as an organic substrate in the vegetative propagation of the dragon fruit tree by providing increments of the vegetative characters and biomass production, confirmed by the greater inputs of nutrients accumulated in its plant tissue.

Changes in the chemical properties of coir dust with increasing aging time and development of a method for determining moderate aging degree

The objective of this study was to create a method to evaluate the aging of coir dust. A rainproof plastic house was used to monitor the fresh coir dust for 24 weeks, and the samples were collected every 2 weeks during aging. The aging effects on coir dust were investigated with the changes in mineral nutrient contents and plug seedling growth in four different vegetables. Experiments were conducted to determine the appropriate degree of aging by analyzing the changes of total phenol and tannin contents, color, and near-infrared spectral characteristics as influenced by the aging duration of coir dust. The pH, electrical conductivity (EC), and cation exchange capacity (CEC) values of the non-aged coir dust were 5.04, 9.19 dS m−1, and 75.2 cmol+ kg−1, respectively. The concentrations of Cl and K in the non-aged coir dust were 4061.8 and 3487.4 mg kg−1, respectively. The contents of total phenol and tannin in the non-aged coir dust were 168.8 and 38.8 mg kg−1, respectively. The pH rose continuously to 5.94 at 24 weeks, and the EC decreased to 1.8 dS m−1 after 4 weeks of aging and then remained at a similar level. The concentrations of elements decreased drastically except for NH4+ and NO3− until 4 weeks of aging, and later they remained at a similar level. The total phenol content decreased greatly at 2 weeks of aging, and the tannin content decreased continuously from 38.8 mg kg−1 in week 0 to 0.15 mg kg−1 at 24 weeks of aging. The color indicators b* and C* decreased until 12 weeks of aging, and after that, they remained at a similar level. The optimum aging of coir dust was judged based on b* and C* values. The spectral analysis showed that the coir dust aged over 18 weeks could be distinguished from the earlier stage of aging with 91% accuracy. When the coir dust with varied aging durations was used as a root substrate, the fresh weights of radish, Korean cabbage, tomato, and red pepper increased quadratically as the aging period of the coir dust became longer (R2 = 0.7824, 0.7529, 0.4718, and 0.5458 in radish, Chinese cabbage, tomato, and red pepper, respectively; p ≤ 0.001).

Influence of pre-plant root substrate nitrogen levels on growth of selected fruit bearing vegetable seedlings in cylindrical paper pots

In raising vegetable seedlings using cylindrical paper pots, the root substrates inside paper pots dry out fast mainly due to air spaces between paper pots created by chinks between the pot’s exterior and the holding tray. Frequent watering is necessary that contributes to the loss of nutrients by leaching during seedling production. This study was carried out to investigate the appropriate concentration of nitrogen required as a pre-planting fertilizer for growing fruit-bearing vegetable seedlings in cylindrical paper pots. For the experiment, the paper pots were made with the root substrate containing perlite (1–3 mm) and peat moss (10-mesh, 10–20% by volume) and they were placed into the 40-cell trays. The concentrations of all essential elements except nitrogen was equal in all treatments and the N concentration was adjusted to 0, 150, 250, 500, and 750 mg L−1 during the substrate formulation. Then, seedling grafts of cucumber, watermelon and tomato were transplanted and seeds of hot pepper were sown directly into the paper pots. The growth of cucumber, watermelon, and tomato plants were measured at 15, 18, and 21 days after transplanting and pepper at 5 weeks after seed sowing. The concentrations of macro-elements, pH, and EC of root substrates were analyzed every week. The pH of root substrates gradually increased during the seedling growth, but the differences in pH among N treatments is not significant. The EC in all treatments did not changed until one week after the transplanting of cucumber, watermelon, and tomato seedling grafts and 3 weeks after seed sowing of pepper. The concentration of Ca remained similar over time during the entire experimental period, but the concentration of Mg and K decreased 3 weeks after the seed sowing for the pepper growing root substrate. The concentrations of Ca, Mg, and K gradually decreased after one week of transplantation (cucumber, watermelon, and tomato). Based on the results, the optimal concentration of N required is 250 mg L−1 for tomato and 500 mg L−1 for cucumber, watermelon, and pepper respectively. In summary, the appropriate N concentration in the root substrate of paper pot is 250–500 mg L−1, and post-planting fertilization period is 1 week after transplanting for cucumber, watermelon and tomato and 3 weeks after seed sowing for hot pepper.

Changes in fine root decomposition of primary Pinus koraiensis forest after clear cutting and restoration succession into secondary broad-leaved forest

Fine root decomposition is one of the primary mechanisms by which nutrient uptake and C exchange occur in terrestrial ecosystems, which will be likely affected by forest succession. Herein, we compared the fine root decomposition rates of primary Korean pine forest (PK) and secondary broad-leaved forest (SF) using the litter bag method; then conducted an in-depth analysis of differences in the PK and SF fine root decomposition process. Our results demonstrated that the fine root decomposition in PK was significantly faster than that in SF. In general, the percent (%) mass of the main nutrient elements remaining in SF fine roots was significantly higher than that in PK, indicating that PK can more efficiently return soil nutrients through fine root decomposition. We also found that the succession of PF to SF induced significant alternation of the microbial community composition and decreased activities of soil enzymes. Structural equation modeling further demonstrated that fine root K and lignin were the key substrate-level factors affecting fine root decomposition, while actinomycetes and fungi PLFA biomass change played the most important role among all the functional groups. Finally, we determined that fine root degradation was driven by polyphenol oxidase and acid phosphatase enzymatic activities. This study elucidates the complex interactions between fine root substrate and soil physiochemical properties and demonstrates how they affect fine root decomposition via soil microorganisms. Given that these changes continue over long time scales, the secondary forest will experience increased difficulty return to the original primary Korean pine broad-leaved forest vegetation.