Root Length Production Research Articles

Initial Development of Corn Seedlings after Seed Priming with Nanoscale Synthetic Zinc Oxide

Nanofertilizers are increasingly explored for sustainable micronutrient delivery in agriculture. Pre-treating seeds with nanofertilizers prior to planting (i.e., seed priming) reduces concerns about nanoparticle (NP) fertilizer non-target dispersion; however, priming formulations and concentrations must be carefully selected to avoid germination inhibition and toxicity. Here we investigate changes in corn seed germination and seedling development after seed priming with ZnO NPs, ZnO bulk and ZnCl2. To evaluate the effects sterile seeds were immersed in priming solutions of 0, 20, 40, 80, 160 mg L−1 Zn for the three Zn sources. Following an 8 h priming the seeds were evaluated for germination and vigor for 5 days on germination paper. Root and shoot lengths were measured as well as fresh and dry biomass. Compared to the control, the ZnO NP and ZnCl2 seed priming promoted beneficial effects. ZnO NP seed-priming exhibited a concentration dependent profile in improving seedling growth, with greatest benefit around 80 mg L−1, providing 17%, 25% and 12% higher values than control for germination, root length, and dry biomass production, respectively. In contrast, seeds primed with bulk ZnO did not differ from the control. These findings support NP-seed priming as an alternative to delivery of essential micronutrients, such as zinc, to corn seedlings.

Pioneer root invasion and fibrous root development into disturbed soil space observed with a flatbed scanner method

Fine roots with thick diameter preferentially elongated into disturbed soil space, indicating positive invasion of pioneer roots that recolonize distal root systems. Fine roots and their morphological traits are related to below-ground resource dynamics at physiological and ecological levels. Established approaches for investigating fine root dynamics inevitably cause artificial soil disturbance due to root excavation or instrument installation into the soil. Soil disturbance can have considerable effects on fine root dynamics. The aim of the present study was to clarify the temporal changes of morphological traits of fine roots produced after soil disturbance. The flatbed scanner method was employed in cypress (Chamaecyparis obtusa Endl.) and deciduous oak (Quercus serrata Thunb.) stands, and changes in length and diameter of elongated roots were measured for 4 years after soil disturbance. In both stands, specific trends of diameter and length production of fine roots were observed. Root length production increased extensively, and diameter was greater in an initial phase after soil disturbance. However, temporal patterns varied between the two stands. Soil disturbance affected fine root dynamics for a longer duration in the cypress stand, but more intensively in the oak stand. These results indicate that soil disturbance can affect fine root morphology and can induce invasion of thick fine roots, which are traditionally grouped as pioneer roots. Moreover, the results showed high length production continued for a longer period than that of larger diameter roots, suggesting recolonization of fine root systems by elongating pioneer roots followed by the branching of absorptive fibrous roots in order to recover root uptake capacity lost due to soil disturbance.

Morpho-physiological and biochemical responses of finger millet (Eleusine coracana (L.) Gaertn.) genotypes to PEG-induced osmotic stress

Abstract The effect of PEG-induced (0–25%) osmotic stress was studied in twelve diverse indigenous finger millet genotypes under various levels. With the increasing PEG concentration germination percentage, shoot length, root length, and biomass production decreased in all the genotypes. Among all the genotypes evaluated, reduction in germination percentage, seedling growth, and biomass production was more in FM/RT/01 and less in FM/ST/01. Principal component analysis (PCA) resulted in the formation of three distinct clusters, stress-sensitive (FM/RT/01, FM/RT/03, FM/SD/01, and FM/ST/02), stress-tolerant (FM/ST/01, FM/ST/03, and FM/KP/02) and moderately tolerant/sensitive (FM/KP/01, FM/RT/02, FM/RT/04, FM/RT/05, and FM/RG/01). Based on the germination percentage and growth parameters, FM/RT/01 was considered as PEG-induced osmotic stress-sensitive, and FM/ST/01 as stress-tolerant genotype. PEG-induced stress increases membrane damage (MDA content) and osmolyte accumulation (free proline, glycine betaine, and total soluble sugars) in both the genotypes. Damage to the membrane was found more in the stress-sensitive genotype (FM/RT/01) compared to stress-tolerant (FM/ST/01). The magnitude of increase in osmolyte accumulation was more in FM/ST/01 than FM/RT/01. Antioxidative enzyme activities (SOD, CAT, APX, and GPX) significantly increased with increasing PEG 6000 concentration up to 15% PEG but decreased at higher concentrations (20 and 25%) in both the genotypes. Our findings suggests, genotype FM/ST/01 genotype can be exploited for different crop improvement programs.

24-epibrassinolide triggers cadmium stress mitigation in Cucumis sativus through intonation of antioxidant system

The core objective of current study was to find out the potential of 24-epibrassinolide (24-EBL) in alleviation of cadmium (Cd) induced stress in cucumber (Cucumis sativus L.). C. sativus seeds were primed with 5 μM 24-EBL and allowed to grow in Cd spiked petri dishes for 15 days. The Cd-driven stress exhibited noticeable injurious effects on growth parameters of C. sativus seedlings. The oxidative stress pledged due to overproduction of malondialdehyde (MDA) and reactive oxygen species (ROS) severely affected morphological features besides gas exchange parameters, leaf relative water content (LRWC) and amount of photosynthetic pigments in C. sativus seedlings under Cd stress. Nevertheless, 24-EBL reduced Cd contents in cucumber foliage and elucidated the vital role of this biomolecule in Cd translocation. The exogenous application of 24-EBL improved shoot length, root length and biomass production of Cd-stressed plants. Alternatively, 24-EBL triggered reduction in lipid peroxidation besides increased synthesis of ethylene and indole acetic acid (IAA). Furthermore, 24-EBL modulated the expression level of ethylene receptor genes including CS-ERS, 1-aminocyclopropane-1-carboxylate oxidase2 (CsAOX), 1-aminocyclopropane-1-carboxylate oxidase1 (CSACO1), 1-aminocyclopropane-1-carboxylate oxidase2 (CSACO2), and indole acetic related CS 453. Altogether, these physiological vicissitudes advocate that 24-EBL augmented antioxidative capability contributes in the advancement of Cd tolerance in cucumber seedlings.

2-Hydroxymelatonin induced nutritional orchestration in Cucumis sativus under cadmium toxicity: modulation of non-enzymatic antioxidants and gene expression

2-Hydroxymelatonin (2-OHMT) is an important metabolite produced through melatonin interaction with oxygenated compounds. 2-OHMT pretreated seeds (50 µM, 100 µM, and 150 µM) were grown in soil contaminated with 50 mg kg−1 cadmium. Cadmium imposed stress reduced seed germination, growth, biomass production, and chlorophyll (Chl) content in Cucumis sativus seedlings. 2-OHMT application emphatically revamped germination, shoot length, root length, and plant biomass production. The 2-OHMT pretreatment modulated expression levels of plasma membrane H+-ATPase genes of C. sativus including CsHA2, CsHA3, CsHA4, CsHA8, and CsHA9. This biomolecule amplified the accumulation of antioxidants such as glutathione, proline, phenolics, and flavonoids. The reduced Cd-uptake in 2-OHMT treated C. sativus seedlings encouraged uptake of essential plant nutrients. Furthermore, conjugated increase of indole acetic acid contents and ethylene production rate were observed in 2-OHMT treated seedlings in a dose-dependent manner. The improved nutritional content in 2-OHMT applied seedlings was ascribed to enhanced expression of H+-ATPase regulating genes besides increased amount of non-enzymatic antioxidants in Cd-stressed plants. The present novel study elucidates the potential of 2-OHMT in improving nutritional content in cucumber plants by modulation of non-enzymatic antioxidants and gene expression.

Root production, mortality and turnover in soil profiles as affected by clipping in a temperate grassland on the Loess Plateau

Abstract Aims Clipping or mowing for hay, as a prevalent land-use practice, is considered to be an important component of global change. Root production and turnover in response to clipping have great implications for the plant survival strategy and grassland ecosystem carbon processes. However, our knowledge about the clipping effect on root dynamics is mainly based on root living biomass, and limited by the lack of spatial and temporal observations. The study aim was to investigate the effect of clipping on seasonal variations in root length production and mortality and their distribution patterns in different soil layers in semiarid grassland on the Loess Plateau. Methods Clipping was performed once a year in June to mimic the local spring livestock grazing beginning from 2014. The minirhizotron technique was used to monitor the root production, mortality and turnover rate at various soil depths (0–10, 10–20, 20–30 and 30–50 cm) in 2014 (from 30 May to 29 October) and 2015 (from 22 April to 25 October). Soil temperature and moisture in different soil layers were also measured during the study period. Important Findings Our results showed that: (i) Clipping significantly decreased the cumulative root production (P < 0.05) and increased the cumulative root mortality and turnover rates of the 0–50 cm soil profile for both years. (ii) Clipping induced an immediate and sharp decrease in root length production and an increase in root length mortality in all soil layers. However, with plant regrowth, root production increased and root mortality decreased gradually, with the root production at a depth of 30–50 cm even exceeding the control in September–October 2014 and April–May 2015. (iii) Clipping mainly reduced root length production and increased root length mortality in the upper 0–20 cm soil profile with rapid root turnover. However, roots at deeper soil layers were either little influenced by clipping or exhibited an opposite trend with slower turnover rate compared with the upper soil profile, leading to the downward transport of root production and living root biomass. These findings indicate that roots in deeper soil layers tend to favour higher root biomass and longer fine root life spans to maximize the water absorption efficiency under environmental stress, and also suggest that short-term clipping would reduce the amount of carbon through fine root litter into the soil, especially in the shallow soil profile.

Role of trees and herbaceous vegetation beneath trees in maintaining arbuscular mycorrhizal communities in temperate alley cropping systems

Better understanding of belowground interactions in agroforestry systems is crucial for the success of plant co-existence. Beyond root competition, associated arbuscular mycorrhizal (AM) fungi can also be involved in plant to plant interactions. Thus far, the contribution of each agroforestry component (trees, herbaceous vegetation beneath trees -HVbT- and crops) in the establishment and maintenance of AM communities is poorly documented, particularly in temperate areas. This study investigates the spatio-temporal dynamics of both roots and AM fungi in two alley-cropping sites located in southwestern France. Over a one-year period, (i) root length density, production and distribution, (ii) AM activity (root mycorrhization rate and extra-radical hyphal production) and (iii) AM diversity (metabarcoding) were assessed at different distances from tree rows in two agroforestry systems. The mycorrhization rate and hyphal production increased at the interface between tree rows and cultivated alleys, showing a positive effect of the presence of a perennial system (tree and HVbT) and of plant diversity. Compared to HVbT, tree roots colonized farther into superficial layers of the cultivated alleys. However, due to higher root densities and well-established AM fungi observed throughout all the year, HVbT appeared to be more relevant in maintaining an active source of AM inoculum for newly developing crop roots in winter. The spatial proximity of roots and common AM fungi provides new perspectives in deciphering the significance of arbuscular mycorrhizal communities in crop nutrition and yield in agroforestry systems.

Physiological mechanisms of exogenous calcium on alleviating salinity-induced stress in rice (Oryza sativa L.).

Being more sensitive to salt stress among the cereals, growth of rice (Oryza sativa L.) has been habitually affected by salinity. Although, several practices have evolved to sustain the growth of rice under salinity, the enormous role of calcium (Ca2+) as a signalling moleculein salt stress mitigation is still arcane. Considering this fact, an experiment was performed aiming to explicate the mechanism of salt-induced growth inhibition in rice and its alleviation by exogenous Ca2+. At germination stage, 10mM and 15mM CaCl2 primed rice (cv. Binadhan-10 & Binadhan-7) seeds were grown in petri dishes for 9days under 100mM NaCl stress. At seedling stage, 9-day-old rice seedlings grown on sandwere exposed to 100mM NaCl alone and combined with 10mM and 15mM CaCl2 for 15days. This research revealed that salinity radically slowed down growth of rice seedlings and Ca2+ treatment noticeably improved growth performances. At germination stage, 10mM CaCl2 treatment significantly increased the final germination percentage, germination rate index (in Binadhan-7), shoot, root length (89.20, 67.58% in Bindhan-10 & 84.72, 31.15% in Bindhan-7) and biomass production under salinity. Similarly, at seedling stage, 10mM CaCl2 supplementation in salt-stressed plants enhanced shoot length (42.17, 28.76%) and shoot dry weight (339.52, 396.20%) significantly in Binadhan-10 & Binadhan-7, respectively, but enhanced root dry weight (36.76%) only in Binadhan-10. In addition, 10mM CaCl2 supplementation on salt-stressed seedlings increased the chlorophyll and proline content, and oppressed the accretion of reactive oxygen species thus protecting from oxidative damage more pronouncedly in Binadhan-10 than Binadhan-7 as reflected by the elevated levels of catalase and ascorbate peroxidase activity. The 15mM CaCl2 somehow also enhanced some growth parameters but overall wasless effective than 10mM CaCl2 to alleviate salt stress, and sometimes showed negative effect. Therefore, supplementary application of calcium-rich fertilizers in saline prone soils can be an effective approach to acclimatize salt stress and cultivate rice successfully.

Insecticidal Effects of Some Plant Leaf Extracts in the Control of Insect Field Pests of Amaranthus hybridus L

A field trail was conducted at the Botanical garden of department of Plant Science and Biotechnology, Abia State University, Uturu, Nigeria to assess the insecticidal effect of aqueous leaf extracts of Azadirachta indica, Ocimum gratisimum and Vernonia amygdalina on insect field pests of Amaranthus hybridus. The experimental design was randomized complete block with three replicates. Aqueous leaf extracts of the powdered samples of these plants were uniformly sprayed on the experimental material at 30 g/l twice weekly from 10 to 38 days after sowing. A. hybridus plants sprayed with aqueous leaf extracts of the different plants had lower percentage leaf and leaf area damage compared to the control. Percentage leaf damage followed this order: A. indica < V. amygdalina < O. gratisimum < control, with percentages leaf damage of 25-27%, 34-46%, 32-49% and 47-73%, respectively. Percent leaf area damage were 18.6%, 31%, 45.8% and 61.2% for A. indica, O. gratisimum, V. amygdalina and control, respectively. Significantly (P<0.05) higher plant height, root length and dry matter production were obtained in plants sprayed with aqueous leaf extract of A. indica in contrast to the other treatments, which had comparable values with the control. The results indicate that A. indica if properly harnessed can be used as a biopesticide in the control of insect field pest of A. indica .

Effect of Compost Application on the Growth of Acacia nilotica

Abstract Acacia nilotica is an important agroforestry specie, which is used in both compact and linear forms. The objective of the current study was to evaluate the effect of compost on the growth performance and biomass production of A. nilotica. Completely randomized design (CRD) was used to analyze the variations among several growth morphological traits. Two parallel trials, pot trial (seedlings), field trial (saplings) were conducted simultaneously. Compost and litter mixture were applied in mentioned trials. Following treatments were used: T0 – control; T1 - 25% of compost and 75% of nursery soil; T2 - mixture of 50% nursery soil and 50% compost; T3 - mixture of 75% compost and 25% of nursery soil; T4 - where 100% compost was applied. Increase in plant growth was observed with the increases in the amount of compost mixture. In field trial maximum plant height, shoot length, root length, rootshoot ratio and biomass production was observed when 100% compost level was applied, while minimum was observed without any compost appli-cation. In pot trials, the maximum plant height, rootshoot ratio and biomass production was recorded when 75% compost level was applied. Overall, Acacia performed better with 100% of compost application in field trail and 75% of compost application in pot trial. The results of this study demonstrated the positive effects of compost on the growth of Acacia. The seedling development was improved considerably with different levels having greater percentage of organic fertilizer and it was concluded that compost improves soil fertility and it should be used as organic fertilizer in farming and forestry practices for improving crop growth and yield.

Interactions Between Light Intensity and Phosphorus Nutrition Affect the P Uptake Capacity of Maize and Soybean Seedling in a Low Light Intensity Area.

To capture more nutrients, root systems of maize (Zea mays L.) and soybean (Glycine max L.) exhibit morphological and physiological plasticity to a localized supply of phosphorus (P). However, the mechanisms of the interaction between light intensity and P affecting root morphological and physiological alterations remain unclear. In the present study, the regulation of P uptake capacity of maize and soybean by light intensity and localized P supply was investigated in a low solar radiation area. The plants were grown under continual and disrupted light conditions with homogeneous and heterogeneous P supply. Light capture of maize and soybean increased under the disrupted light condition. Plant dry weight and P uptake were increased by more light capture, particularly when plants were grown in soil with heterogeneous P supply. Similarly, both localized P supply and disrupted light treatment increased the production of fine roots and specific root length in maize. Both homogeneous P supply and disrupted light treatment increased the malate and citrate exudation in the root of soybean. Across all of the experimental treatments, high root morphological plasticity of maize and root physiological plasticity of soybean were associated with lower P concentrations in leaves and greater sucrose concentrations in roots. It is suggested that the carbon (C), exceeded shoot growth capabilities and was transferred to roots as sucrose, which may serve as both a nutritional signal and a C-substrate for root morphological and physiological changes.

Effect of Different Organic Addition on Seedling Growth and Stump Quality of Teak (Tectona grandis Linn f.)

A nursery experiment was conducted to study the effect of different organic addition in the nursery on growth and stump quality of teak seedling. The nursery soil sample was analyzed before initiate the experiment and after uprooting the seedling from nursery (post harvest soil). The pre conditioned 6 months-old teak drupes (fruit with seed) were placed for germination in the nursery bed. The experiment consisted of eight treatments which replicated thrice. On 28 and 60 days after sowing, the result revealed that the application of organic amendments did not have any significant effect on number of seedlings /m2 of teak at 28 days after sowing, where as the significant influence were observed at 60 days after sowing. Significant differences were observed in root length (cm), shoot length (cm), stump weight (g), stump girth (mm) and dry matter production (g) of teak stump at 6 months after sowing. From this study it could be concluded that the organic addition of teak nursery with FYM @ 12.5 t ha-1 + bagasse fly ash @ 20 t ha-1 enhance the seedling growth and stump quality of 6 months old teak nursery.

PENGARUH PEMBERIAN Bacillus aryabhattai TERHADAP PENINGKATAN POPULASI BAKTERI PENAMBAT N SIMBIOTIK DAN PENINGKATAN PRODUKSI TANAMAN BAWANG DAUN

Green onion is one of the vegetable commodities that have high economic value and high preferable by the community. Green onion has been exported to the other countries. To increase production it is necessary to use technology to fulfill market demand. The One of technology is adding bacteria in the cultivation of the plant. Bacillus aryabhattai is a bacterium that rapidly colonizes the roots of host plants, promotes plant growth, increases the availability of good nutrition, and has antagonistic effects on plant pathogens. The aim of this research is to know the effect of Bacillus aryabhattai in increasing the population of symbiotic N-stimulating bacteria and to increase crop production. The research was carried out at screen house and laboratory of Agricultural Environment Research Center. The soil was andosol soil from Kaliangkrik Subdistrict of Magelang district. The study was conducted from December 2016 to March 2017. The study design was a randomized block design with 4 treatments and 6 replications. The treatments include control (D1), Bacillus aryabhattai (D2), POC (D3), Trichoderma (D4). The results showed that D2 treatment had a high bacterial population and positively affected plant height, root length, root weight and leaf production. The conclusion of Bacillus aryabhattai giving great influence in multiplying the population of symbiotic N binding bacteria, thus increasing the production of green onion.

Multivariate analysis of sesame genotypes under saline stress

Sesame is notable for its rich antioxidants and sesame oil is also familiar for its resistance to oxidation. The cultivation of sesame is usually restricted under abiotic stress conditions. Hence in order to study the performance of sesame genotypes to saline stress, an experiment was conducted to screen ten ruling varieties of sesame viz., CO1, SVR1, SVPR1, VRI 1, VRI 2, TMV 3, TMV 4, TMV 5, TMV 6 and TMV 7 at five different EC levels (EC 1, 2, 3, 4 and 5). Seedling observations namely, germination percentage, speed of germination, shoot length, root length and dry matter production were recorded. Among the genotypes, it was found that under higher saline conditions (EC5), VRI 1 recorded higher seedling length (2.0 cm), vigour index I (100) and vigour index II (1.15), whereas under normal condition, TMV 4 and CO 1 performed better. In general, there was a decrease in all the seedling parameters with increased levels of salinity. With STAR software, Multivariate analysis was done and on the basis of dendrogram, five clusters were formed and the cophenotic correlation co- efficient was found highest in Control (0.912) followed by EC 2 ( 0.829).

Halotolerant plant-growth promoting rhizobacteria modulate gene expression and osmolyte production to improve salinity tolerance and growth in Capsicum annum L.

Some rhizobacteria have demonstrated a noteworthy role in regulation of plant growth and biomass production under biotic and abiotic stresses. The present study was intended to explicate the ameliorative consequences of halotolerant plant growth-promoting rhizobacteria (HPGPR) on growth of capsicum plants subjected to salt stress. Salt stress was ascertained by supplementing 1 and 2g NaCl kg-1 soil. The HPGPR positively invigorated growth attributes, chlorophyll, protein contents, and water use efficiency (WUE) of supplemented capsicum plants under salinity stress conditions. Bacillus fortis strain SSB21 caused highest significant increase in shoot length, root length, and fresh and dry biomass production of capsicum plants grown under saline conditions. This multi-trait bacterium also increased biosynthesis of proline and up-regulated the expression profiles of stress related genes including CAPIP2, CaKR1, CaOSM1, and CAChi2. On the other hand, B. fortis strain SSB21 inoculated plants exhibited reduced level of ethylene, lipid peroxidation, and reactive oxygen species (ROS). All these together contribute to activate physiological and biochemical processes involved in the mitigation of the salinity induced stress in capsicum plants.

Root responses to elevated CO2, warming and irrigation in a semi‐arid grassland: Integrating biomass, length and life span in a 5‐year field experiment

Abstract Plant roots mediate the impacts of environmental change on ecosystems, yet knowledge of root responses to environmental change is limited because few experiments evaluate multiple environmental factors and their interactions. Inferences about root functions are also limited because root length dynamics are rarely measured. Using a 5‐year experiment in a mixed‐grass prairie, we report the responses of root biomass, length and life span to elevated carbon dioxide (CO2), warming, elevated CO2 and warming combined, and irrigation. Root biomass was quantified using soil cores and root length dynamics were assessed using minirhizotrons. By comparing root dynamics with published results for soil resources and above‐ground productivity, we provide mechanistic insights into how climate change might impact grassland ecosystems. In the upper soil layer, 0–15 cm depth, both irrigation and elevated CO2 alone increased total root length by twofold, but irrigation decreased root biomass and elevated CO2 had only small positive effects on root biomass. The large positive effects of irrigation and elevated CO2 alone on total root length were due to increases in both root length production and root life span. The increased total root length and life span under irrigation and elevated CO2 coincided with apparent shifts from water limitation of plant growth to nitrogen limitation. Warming alone had minimal effects on root biomass, length and life span in this shallow soil layer. Warming and elevated CO2 combined increased root biomass and total root length by c. 25%, but total root length in this treatment was lower than expected if the effects of CO2 and warming alone were additive. Treatment effects on total root length and root life span varied with soil depth and root diameter. Synthesis. Sub‐additive effects of CO2 and warming suggest studies of elevated CO2 alone might overestimate the future capacity of grassland root systems to acquire resources. In this mixed‐grass prairie, elevated CO2 with warming stimulated total root length and root life span in deeper soils, likely enhancing plant access to more stable pools of growth‐limiting resources, including water and phosphorus. Thus, these root responses help explain previous observations of higher, and more stable, above‐ground productivity in these projected climate conditions.

Litter removal in a tropical rain forest reduces fine root biomass and production but litter addition has few effects.

Many old-growth lowland tropical rain forests are potentially nutrient limited, and it has long been thought that many such forests maintain growth by recycling nutrients from decomposing litter. We investigated this by continuously removing (for 10yr) freshly fallen litter from five (45m×45m) plots, adding it to five other plots, there were five controls. From monthly measures over 1 yr we show that litter removal caused lower: fine root (≤2mm diameter) standing mass, fine root standing length, fine root length production and fine root length survivorship. Litter addition did not significantly change fine root mass or length or production. Nutrient concentrations in fine roots in litter removal plots were lower than those in controls for nitrogen (N), calcium (Ca) and magnesium (Mg), concentrations in fine roots in litter addition plots were higher for N and Ca. Chronic litter removal has resulted in reduced forest growth due to lack of nutrients, probably nitrogen. Conversely, long-term litter addition has had fewer effects.

Effect of fertilizer prepared from human feces and straw on germination, growth and development of wheat

Solid waste treatment is one of the most important rate-limiting steps in the material circulation and energy flow of Bioregenerative Life Support System (BLSS). In our previous work, an efficient and controllable solid waste bio-convertor has been built and a solid waste degradation efficiency of 41.0% has been reached during a 105-d BLSS experiment. However, the fermented residues should be further utilized to fulfill the closure of the system. One solution might be to use the residues as the fertilizer for plant cultivation. Thus in this study, substrates were prepared using different ratios of the fermented residues to the vermiculite. And the influences of different ratios of the fermented residues on the seed germination, growth, photosynthetic characteristics and antioxidant capacity of wheat were studied. The results showed that the optimal rate of the fermented residue was 5%. With this ratio, the seed germination reached 97.3% with the root length, shoot length and biomass production as 59 mm, 52 mm and 150 mg, respectively, at the 4th day. Besides, the highest straw height of 25.1 cm was obtained at the 21st day. The salinity adversely affected the growth and some relevant metabolic processes of wheat. The Group-40% led to the lowest seed germination of 34.7% and the minimum straw height of 15 cm. This inhibition might be caused by the high Na content of 2118 mg/kg in the fermented residues. Chlorophyll b was more sensitive to the mineral nutrition stress and affects the wheat photosynthetic characteristics. Higher reactive oxygen species levels and reduced antioxidant enzymes may contribute, directly and/or indirectly, to the decline in the observed pigment contents in wheat.

Contrasting phenology of Eucalyptus grandis fine roots in upper and very deep soil layers in Brazil

While the role of deep roots in major ecosystem services has been shown for tropical forests, there have been few direct measurements of fine root dynamics at depths of more than 2 m. The factors influencing root phenology remain poorly understood, creating a gap in the knowledge required for predicting the effects of climate change. We set out to gain an insight into the fine root phenology of fast-growing trees in deep tropical soils. Fine root growth and mortality of Eucalyptus grandis trees were observed fortnightly using minirhizotrons down to a soil depth of 6 m, from 2 to 4 years after planting. In the topsoil, the highest live root length production was during the rainy summer (20 cm m−2 d−1) whereas, below 2 m deep, it was at the end of the dry winter (51 cm m−2 d−1). The maximum root elongation rates increased with soil depth to 3.6 cm d−1 in the 5–6 m soil layer. Our study shows that the effect of the soil depth on the seasonal variations in fine root growth should be taken into account when modelling the carbon, water and nutrient cycles in forests growing on deep tropical soils.

Fine root phenology differs among subtropical evergreen broadleaved forests with increasing tree diversities

Fine root phenology represents ecological strategy of plants in utilizing soil resources and plays an essential role in carbon and nutrient cycling. Here, we aimed to understand how fine root phenology could change in subtropical broadleaved forests with increasing tree species diversity. Three 37–40 years old Castanopsis carlesii forests with low to high tree species diversity were selected in southern China: a plantation forest (PF), a secondary forest through the assisted regeneration (AR), and a secondary forest through natural regeneration (NR), with a nearby natural C. carlesii forest as a control. Fine root length production in these forests was measured monthly during January 2013 to December 2014 using minirhizotron, and fine root production phenology and its correlations with environmental factors were compared among these forests. No significant difference in fine root length production was found among these forests; however, there was distinct fine root phenology. The timing of fine root growth initiation and growth peak was quite stable across the two years in PF, while they were more flexible in AR and NR which were higher in tree species diversity. However, the timing of fine root growth cessation was quite fixed for all the forests. The duration and inter-annual stability of fine root growth both decreased with increasing tree species diversity. Moreover, the correlations of monthly fine root production with monthly air and soil temperature both increased with increasing tree species diversity. It is concluded that the timing of fine root growth in higher tree species diversity stand seems more flexible and more synchronous with seasonal and annual fluctuations of soil resources caused by weather variability, which helps our understanding of the relationships between tree diversity and ecosystem carbon and nutrient cycling.