Root Uptake Capacity Research Articles

Scion-to-Rootstock Mobile Transcription Factor CmHY5 Positively Modulates the Nitrate Uptake Capacity of Melon Scion Grafted on Squash Rootstock

It is generally recognized that the root uptake capacity of grafted plants strongly depends on the rootstocks' well-developed root system. However, we found that grafted plants showed different nitrate uptake capacities when different varieties of oriental melon scion were grafted onto the same squash rootstock, suggesting that the scion regulated the nitrate uptake capacity of the rootstock root. In this study, we estimated the nitrate uptake capacity of grafted plants with the different oriental melon varieties' seedlings grafted onto the same squash rootstocks. The results indicated a significant difference in the nitrate uptake rate and activity of two heterologous grafting plants. We also showed a significant difference in CmoNRT2.1 expression in the roots of two grafting combinations and verified the positive regulation of nitrate uptake by CmoNRT2.1 expression. In addition, the two varieties of oriental melon scion had highly significant differences in CmHY5 expression, which was transported to the rootstock and positively induced CmoHY5-1 and CmoHY5-2 expression in the rootstock roots. Meanwhile, CmHY5 could positively regulate CmoNRT2.1 expression in the rootstock roots. Furthermore, CmoHY5-1 and CmoHY5-2 also positively regulated CmoNRT2.1 expression, respectively, and CmoHY5-1 dominated the positive regulation of CmoNRT2.1, while CmHY5 could interact with CmoHY5-1 and CmoHY5-2, respectively, to jointly regulate CmoNRT2.1 expression. The oriental melon scion regulated the nitrate uptake capacity of the melon/squash grafting plant roots, and the higher expression of CmHY5 in the oriental melon scion leaves, the more substantial the nitrate uptake capacity of squash rootstock roots.

Root Electrical Capacitance Can Be a Promising Plant Phenotyping Parameter in Wheat.

As root electrical capacitance (CR*) was assumed to depend on the stem properties, the efficiency of measuring CR* at flowering for whole-plant phenotyping was assessed in five wheat cultivars in three replicate plots over two years. Linear regression analysis was used to correlate CR* with plant-size parameters and flag-leaf traits (extension and SPAD chlorophyll content) at flowering, and with yield components at maturity. The plot-mean CR* was correlated with the plot leaf area index (LAI), the chlorophyll quantity (LAI×SPAD), and the grain yield across years. At plant scale, CR* was found to show the strongest positive regression with total chlorophyll in the flag leaf (flag leaf area × SPAD; R2: 0.65-0.74) and with grain mass (R2: 0.55-0.70) for each cultivar and year (p < 0.001). Likewise, at plot scale, the regression was strongest between CR* and the LAI×SPAD value (R2: 0.86-0.99; p < 0.01) for the cultivars. Consequently, CR* indicated the total plant nutrient and photosynthate supply at flowering, which depended on root uptake capacity, and strongly influenced the final yield. Our results suggested that the polarization of the active root membrane surfaces was the main contributor to CR*, and that the measurement could be suitable for evaluating root size and functional intensity. In conclusion, the capacitance method can be applied for nondestructive whole-plant phenotyping, with potential to estimate root and shoot traits linked to the nutrient supply, and to predict grain yield. CR* can be incorporated into allometric models of cereal development, contributing to optimal crop management and genetic improvement.

Comparative transcriptome analysis between inbred lines and hybrids provides molecular insights into K+ content heterosis of tobacco (Nicotiana tabacum L.).

Potassium (K+) is essential for crop growth. Increasing the K+ content can often directly promote the improvement of crop yield and quality. Heterosis plays an important role in genetic improvement and leads to genetic gains. We found that the K+ content of tobacco showed significant heterosis, which is highly significant for cultivating tobacco varieties with high K+ content. However, the mechanism by which K+ content heterosis occurs in tobacco leaves is not clear. In this study, a comprehensive comparative transcriptome sequencing analysis of root samples from the hybrid G70 × GDH11 and its parental inbred lines G70 and GDH11 was performed to elucidate the importance of the root uptake capacity of K+ in the formation of heterosis. The results showed that 29.53% and 60.49% of the differentially expressed genes (DEGs) exhibited dominant and over-dominant expression patterns, respectively. These non-additive upregulated DEGs were significantly enriched in GO terms, such as metal ion transport and reaction, ion balance and homeostasis, ion channel activity, root meristem growth, and regulation of root hairs. The KEGG annotation results indicated that these genes were mainly involved in the pathways such as energy metabolism, carbohydrate formation, amino acid metabolism, and signal transduction. Further analysis showed that probable potassium transporter 17 (NtKT17) and potassium transporter 5-like (NtKT5), associated with potassium ion absorption, glutamate receptor 2.2-like and glutamate receptor 2.8-like, associated with ion channel activity, LOC107782957, protein detoxification 42-like, and probable glutamate carboxypeptidase 2, associated with root configuration, showed a significantly higher expression in the hybrids. These results indicated that the over-dominant expression pattern of DEGs played a key role in the heterosis of K+ content in tobacco leaves, and the overexpression of the genes related to K+ uptake, transport, and root development in hybrids helped to improve the K+ content of plants, thus showing the phenomenon of heterosis.

Stenocereus queretaroensis a source of endophytic plant growth promoting bacteria for cropping Zea mays

Healthy growth of Zea mays requires NH4NO3 as nitrogen fertilizer (NF), and its uptake is important to avoid loss of the NF. An alternative solution to enhance the root uptake capacity of Z. mays of NF at a dose to supply Z. mays demand without compromise its health; with beneficial entophytic genera and species of Stenocereus queretaroensis of the type Burkholderia vietnamiensis and Gluconacetobacter diazotrophicus. The objectives of this research were: a) to select from the interior of roots of Stenocereus queretaroensis: B. vietnamiensis and G. diazotrophicus, b) to analyze the growth of Z. mays with B. vietnamiensis and G. diazotrophicus and NF at 50%. B. vietnamiensis and G. diazotrophicus were recovered from the roots of S. queretaroensis and inoculated on Z. mays seed with NF. Using the response variables: percentage of emergency, phenology and biomass to seedling and flowering, the experimental data were analyzed by ANOVA-Tukey (P ≤ 0.05). The percentage of emergency, phenology, and biomass at seedling and flowering of Z. mays with B. vietnamiensis and G. diazotrophicus at 50% of NH4NO3, registered numerical values with statistical difference compared to those obtained in Z. mays without B. vietnamiensis and G. diazotrophicus only with NF at 100% or relative control (RC). This supports that B. vietnamiensis and G. diazotrophicus, entophytes of S. queretaroensis, invading the interior of Z. mays roots, converted metabolites related to root physiology into phytohormones that allowed maximum root uptake of NH4NO3 at 50%

Inferred seasonal alternation in the anatomical structures determining maximum transpiration rate in upland boreal stand types

AbstractIn the boreal forest the water‐absorbing fraction of the root network undergoes an annual cycle of growth and dieback that is positively correlated with soil temperature. This study is a modelling exercise that uses duff temperature as a proxy for root uptake capacity to gain insight into its potential influence on the seasonal dynamics of maximum transpiration rate. Atmospheric and soil variables were measured hourly over six growing seasons in four boreal stand types. Empirical drying models predicting the relative contribution of evaporation and transpiration to the hourly change in duff moisture content were developed for periods when precipitation was not adding water and bulk flow was not removing it. The transpiration model was effective at predicting duff moisture loss in the springtime and late autumn but underestimated it in the intervening period. This divergence could be corrected by replacing the model's duff‐temperature input variable with a calibrated fixed value between 15°C and 24°C. These findings suggest that root uptake capacity is the dynamic limiting factor to maximum transpiration rate in the spring and late autumn while outflow potential through the fixed number of stomata in the canopy assumes the role during the summer and early autumn once functional equilibrium with root uptake capacity has been established. Deterioration in this three‐phase pattern in later iterations of the study was associated with drought‐induced reductions in transpiration at the same sites in the preceding year and hints at shortfalls in the production of starch needed to initiate fine‐root growth in the spring.

The other side of tropical forest drought: do shallow water table regions of Amazonia act as large-scale hydrological refugia from drought?

Tropical forest function is of global significance to climate change responses, and critically determined by water availability patterns. Groundwater is tightly related to soil water through the water table depth (WT), but historically neglected in ecological studies. Shallow WT forests (WT < 5 m) are underrepresented in forest research networks and absent in eddy flux measurements, although they represent c. 50% of the Amazon and are expected to respond differently to global-change-related droughts. We review WT patterns and consequences for plants, emerging results, and advance a conceptual model integrating environment and trait distributions to predict climate change effects. Shallow WT forests have a distinct species composition, with more resource-acquisitive and hydrologically vulnerable trees, shorter canopies and lower biomass than deep WT forests. During 'normal' climatic years, shallow WT forests have higher mortality and lower productivity than deep WT forests, but during moderate droughts mortality is buffered and productivity increases. However, during severe drought, shallow WT forests may be more sensitive due to shallow roots and drought-intolerant traits. Our evidence supports the hypothesis of neglected shallow WT forests being resilient to moderate drought, challenging the prevailing view of widespread negative effects of climate change on Amazonian forests that ignores WT gradients, but predicts they could collapse under very strong droughts.

Root length density (RLD) of oil palm (Elaeis guineensis Jacq) in a haplic Luvisol in Chiapas, Mexico

The tight relationship between root architecture and uptake capacity of soil water and minerals, is well established. Support roots, generally long-lived, perform support functions such as transportation and food storage. Absorbing roots, thin and short-lived, absorb nutrients and regulate plant metabolism. Roots distribution in the soil profile is crucial for plant development. It optimizes resource usage and ensures a prompt response to seasonal changes. This work aimed to study the vertical distribution of the root system of nine-year-old oil palms in a haplic Luvisol, low fertility, moderately acidic, with Nitrogen (N) and Potassium (K) deficiency, average content of Phosphorous (P), and medium to low Cation Exchange Capacity (CEC). Using the cylinder method, soil samples were collected every 10 cm and down to 150 cm of soil depth, from each cardinal side of three soil profiles. The results showed that oil palms had good root development. Most roots (73%) were found in the first 30 cm of soil, with a predominance of fine roots (78%). At 50 cm in depth, fine roots represented 88%, thin roots, 67% and medium roots, 94%. Further study should assess root length density at 15, 20, 25, and 30 years. Highlights - Haplic luvisols are optimal soils for oil palm cultivation due to their depth (&gt; 150cm), over 50% base saturation, and pH of 5.5-6.6. - Root length density (RLD) decreased as soil depth increased. Although most oil palm roots are found in surface horizons, roots can still be found at depths of up to 1.5-5 m. - The highest number of oil palm roots (73%) was found in the first 30 cm, with 78% of fine roots. - Fine roots were distributed throughout the entire soil profile, evidencing high nutrient-absorption and metabolic activities.

Improving maize's N uptake and N use efficiency by strengthening roots' absorption capacity when intercropped with legumes.

Maize’s nitrogen (N) uptake can be improved through maize-legume intercropping. N uptake mechanisms require further study to better understand how legumes affect root growth and to determine maize’s absorptive capacity in maize-legume intercropping. We conducted a two-year field experiment with two N treatments (zero N (N0) and conventional N (N1)) and three planting patterns (monoculture maize (Zea mays L.) (MM), maize-soybean (Glycine max L. Merr.) strip intercropping (IMS), and maize-peanut (Arachis hypogaea L.) strip intercropping (IMP)). We sought to understand maize’s N uptake mechanisms by investigating root growth and distribution, root uptake capacity, antioxidant enzyme activity, and the antioxidant content in different maize-legume strip intercropping systems. Our results showed that on average, the N uptake of maize was significantly greater by 52.5% in IMS and by 62.4% in IMP than that in MM. The average agronomic efficiency (AE) of maize was increased by 110.5 % in IMS and by 163.4 % in IMP, compared to MM. The apparent recovery efficiency (RE) of maize was increased by 22.3% in IMS. The roots of intercropped maize were extended into soybean and peanut stands underneath the space and even between the inter-rows of legume, resulting in significantly increased root surface area density (RSAD) and total root biomass. The root-bleeding sap intensity of maize was significantly increased by 22.7–49.3% in IMS and 37.9–66.7% in IMP, compared with the MM. The nitrate-N content of maize bleeding sap was significantly greater in IMS and IMP than in MM during the 2018 crop season. The glutathione (GSH) content, superoxide dismutase (SOD), and catalase (CAT) activities in the root significantly increased in IMS and IMP compared to MM. Strip intercropping using legumes increases maize’s aboveground N uptake by promoting root growth and spatial distribution, delaying root senescence, and strengthening root uptake capacity.

Mitigation of climate change and environmental hazards in plants: Potential role of the beneficial metalloid silicon

In the last decades, the concentration of atmospheric CO2 and the average temperature have been increasing, and this trend is expected to become more severe in the near future. Additionally, environmental stresses including drought, salinity, UV-radiation, heavy metals, and toxic elements exposure represent a threat for ecosystems and agriculture. Climate and environmental changes negatively affect plant growth, biomass and yield production, and also enhance plant susceptibility to pests and diseases. Silicon (Si), as a beneficial element for plants, is involved in plant tolerance and/or resistance to various abiotic and biotic stresses. The beneficial role of Si has been shown in various plant species and its accumulation relies on the root's uptake capacity. However, Si uptake in plants depends on many biogeochemical factors that may be substantially altered in the future, affecting its functional role in plant protection. At present, it is not clear whether Si accumulation in plants will be positively or negatively affected by changing climate and environmental conditions. In this review, we focused on Si interaction with the most important factors of global change and environmental hazards in plants, discussing the potential role of its application as an alleviation strategy for climate and environmental hazards based on current knowledge.

Plant carbon investment in fine roots and arbuscular mycorrhizal fungi: A cross-biome study on nutrient acquisition strategies

Comparing the belowground allocation of assimilated carbon (C) to roots and mycorrhizal fungi across biomes can reveal specific plant nutrient acquisition strategies in ecosystems and allows to predict consequences of environmental changes. Three natural ecosystems (arid shrubland, coastal matorral, humid-temperate forest) distinct in annual precipitation and vegetation cover and compositions were selected to conduct a 13CO2 pulse labeling of natural woody vegetation to chase the allocation of assimilated C to arbuscular mycorrhizal (AM) fungi and fine roots. Further, nitrogen (N) and phosphorus (P) availability, root traits, root colonization, and the extraradical AM fungal mycelium (PLFA and NLFA 16:1ω5c) were analyzed to evaluate the efficiency of nutrient acquisition strategies. AM fungal colonization decreased with increasing aridity by up to 55% intraradical and by up to 90% extraradical. High root tissue densities – indicating longevity of roots – and low specific root lengths – indicating a low nutrient uptake capacity – pointed to a slow and resource conservative acquisition strategy of plants in the arid shrubland. Plants in the matorral, on the contrary, had lower root tissue densities but higher specific root lengths and higher root N contents, pointing to a fast nutrient acquisition strategy. The expression of abundant acquisitive fine roots of plants in the matorral, however, comes at the cost of larger C investment, shown by high 13C incorporation into root tissue. High root tissue densities and greater root diameter indicated that plants in the humid-temperate forest followed a resource-conservative strategy and outsource their nutrient acquisition to AM fungi. This outsourcing provides an efficient pathway to compensate a low uptake capacity of thick and dense roots. These ecosystem-specific acquisition strategies and distinct mutualism with AM fungi across the biomes will likely affect the sensitivity of plants to abiotic and biotic stressors and, thus, ecosystem responses to future climatic and environmental changes.

Effects of drought on nitrogen uptake and carbon dynamics in trees.

Research on drought impact on tree functioning is focussed primarily on water and carbon (C) dynamics. Changes in nutrient uptake might also affect tree performance under drought and there is a need to explore underlying mechanisms. We investigated effects of drought on (a) in situ nitrogen (N) uptake, accounting for both, N availability to fine roots in soil and actual N uptake, (b) physiological N uptake capacity of roots and (c) the availability of new assimilates to fine roots influencing the N uptake capacity using 15N and 13C labelling. We assessed saplings of six different tree species (Acer pseudoplatanus L., Fagus sylvatica L., Quercus petraea (Mattuschka) Liebl., Abies alba Mill., Picea abies (L.) H.Karst. and Pinus sylvestris L.). Drought resulted in significant reduction of in situ soil N uptake in deciduous trees accompanied by reduced C allocation to roots and by a reduction in root biomass available for N uptake. Although physiological root N uptake capacity was not affected by drought in deciduous saplings, reduced maximum ammonium but not nitrate uptake was observed for A. alba and P. abies. Our results indicate that drought has species-specific effects on N uptake. Even water limitations of only 5weeks as assessed here can decrease whole-plant inorganic N uptake, independent of whether the physiological N uptake capacity is affected or not.

Dynamics of biogenic silica accumulation and ecological characteristics in single-species communities and ecotones in Min River estuary, China

The role of silicon in plant resistance to biotic and abiotic stresses is clear; however, its role in interspecific interactions is not well understood. Biogenic silica (BSi) accumulation and ecological characteristics in single-species communities (Phragmites australis, Cyperus malaccensis, and Spartina alterniflora) and ecotones (P. australis–C. malaccensis and C. malaccensis–S. alterniflora) of Shanyutan marsh, China, were monitored from January to December in 2016. The BSi content of the three plant species decreased at the end of winter and beginning of spring, and continued to increase after March. In ecotones, the density of P. australis, the lengths of C. malaccensis and S. alterniflora, and the BSi content of C. malaccensis were greater than those in single-species communities. However, in single-species communities, the densities of C. malaccensis and S. alterniflora, the length of P. australis, the biomass and BSi stocks of the three species, and the BSi content of P. australis and S. alterniflora were greater than those in the ecotones. The three species may apply different strategies to compete for resources during interactive growth. Phragmites australis may improve its competitive ability by increasing vegetation density, aboveground biomass, and Si allocation to the leaves and withered body. Spartina alterniflora appears to enhance root biomass accumulation and the Si uptake and allocation capacity of roots. Cyperus malaccensis appears to allocate greater biomass and BSi to aboveground organs, as well as improve the absorption capacity of roots to resist competition pressure from P. australis. Cyperus malaccensis mixed with S. alterniflora increased its belowground biomass and BSi stocks. These results help clarify the mechanisms and processes of Si translocation during mixed plant growth, and increase our understanding of the strategies involved in plant competition.

Transporters and ascorbate-glutathione metabolism for differential cadmium accumulation and tolerance in two contrasting willow genotypes.

Salix matsudana Koidz is a low cadmium (Cd)-accumulating willow, whereas its cultivated variety, Salix matsudana var. matsudana f. umbraculifera Rehd., is a high Cd-accumulating and tolerant willow (HCW). The physiological and molecular mechanisms underlying differential Cd accumulation and tolerance in the two Salix species are poorly understood. Here, we confirmed that the differential Cd translocation capacity from roots to the shoots leads to the differential Cd accumulation in their aboveground parts between these two willow genotypes. Cadmium accumulation happens preferentially in the transport pathway, and Cd is mainly located in the vacuolar, cell wall and intercellular space in HCW bark by cadmium location analysis at tissue and subcellular levels. Comparative transcriptome analysis revealed that higher expressions of several metal transporter genes (ATP-binding cassette transporters, K+ transporters/channels, yellow stripe-like proteins, zinc-regulated transporter/iron-regulated transporter-like proteins, etc.) are involved in root uptake and translocation capacity in HCW; meanwhile, ascorbate-glutathione metabolic pathways play essential roles in Cd detoxification and higher tolerance of the Cd-accumulator HCW. These results lay the foundation for further understanding the molecular mechanisms of Cd accumulation in woody plants and provide new insights into molecular-assisted-screening woody plant varieties for phytoremediation.

SUBERMAN regulates developmental suberization of the Arabidopsis root endodermis.

Root endodermis, the innermost cortical layer surrounding the root vasculature, serves as the foremost barrier to water, solutes, and nutrients taken up from soil. Endodermis barrier functionality is achieved via its hydrophobic coating of lignified Casparian strips and the suberin lamellae; nonetheless the regulatory mechanisms underlying endodermis suberization are still elusive. Here, we discovered that the Arabidopsis SUBERMAN (SUB) transcription factor controls the establishment of the root suberin lamellae. Transient expression of SUB in Nicotiana benthamiana leaves resulted in the induction of heterologous suberin genes, the accumulation of suberin-type monomers, and consequent deposition of suberin-like lamellae. We demonstrate that SUB exerts its regulatory roles by transactivating promoters of suberin genes. In Arabidopsis, SUB is expressed in patchy and continuous suberization root endodermal cells, and thus roots with higher or lower expression of SUB display altered suberin polymer deposition patterns and modified composition. While these changes did not interfere with Casparian strip formation they had a substantial effect on root uptake capacity, resulting in varied root and leaf ionomic phenotypes. Gene expression profiling revealed that SUB function impacts transcriptional networks associated with suberin, phenylpropanoids, lignin, and cuticular lipid biosynthesis, as well as root transport activities, hormone signalling, and cell wall modification. Our findings highlight SUB as a regulator of root endodermis suberization during normal development, and its characterization is thus a key step towards dissecting the molecular mechanisms partaking in root endodermal barrier functionalities.

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.

Effects of partial root-zone irrigation and rational close planting on yield and water productivity of cotton in arid area.

The objective of this study was to evaluate the effects and underlying physiological mecha-nisms of partial root zone irrigation (PRI) and rational close planting, as well as their interaction on yield and water productivity (WP) of cotton and to explore new alternatives of water-saving irrigation in dry land areas. A factorial field experiment with irrigation mode (normal irrigation, partial root-zone irrigation and deficient irrigation) and plant population density (135000, 180000 and 225000 plants·hm-2) was conducted in the west of Inner Mongolia to examine their effects on cotton growth, yield, water productivity and related physiological characters. The results showed that the irrigation mode and plant density as well as their interaction significantly affected the biomass, yield, yield components and harvest index. Under normal irrigation, the biomass and the number of bolls per unit area increased with the increasing of plant density, but the harvest index and boll weight significantly reduced. The yield of high plant density was comparable to that of medium plant density, both of which were increased significantly compared with that of low plant density. The content of abscisic acid (ABA) significantly increased and that of auxin (IAA) significantly reduced in cotton leaves under partial root-zone irrigation, which significantly increased the harvest index by improving the partitioning of assimilates to reproductive organs under partial root-zone irrigation. The number of bolls per unit area increased and boll mass remained unchanged with the increasing of density under partial root-zone irrigation. The yield of high density increased by 6.7% and 11.5% compared with that of medium and low density under partial root zone irrigation. The pre-frost seed cotton increased by 22.5%, the amount of irrigation reduced by 30%, and water productivity increased by 49.3% under partial root zone irrigation compared with that under normal irrigation at high plant density. Plant density did not affect photosynthetic rate (Pn) of functional leaves, but irrigation mode significantly affected Pn. Deficient irrigation significantly reduced the Pn of the main-stem functional leaves, but the Pn under partial root-zone irrigation was comparable to that of normal irrigation. The jasmonate (JA) content and the expression level of plasma membrane intrinsic protein (PIP) gene were significantly increased in the hydrated root under partial root-zone irrigation compared with those under normal irrigation. The results suggested that the increased JA content, as a signal molecule, up-regulated the expression level of PIP gene in dehydrated root and increased water uptake capacity of roots and guaranteed water balance of leaves, and then contributed to a relatively high Pn. Partial root-zone irrigation combined with relatively high plant density (225000 plants·hm-2) is an important agronomic alternative for water saving in cotton plantation in the dry land areas.

Water and nutrient uptake capacity of leaf-absorbing trichomes vs. roots in epiphytic tank bromeliads

The water and nutrient uptake mechanisms used by vascular epiphytes have been the subject of a few studies. While leaf absorbing trichomes (LATs) are the main organ involved in resource uptake by bromeliads, little attention has been paid to the absorbing role of epiphytic bromeliad roots. This study investigates the water and nutrient uptake capacity of LATs vs. roots in two epiphytic tank bromeliads Aechmea aquilega and Lutheria splendens. The tank and/or the roots of bromeliads were watered, or not watered at all, in different treatments. We show that LATs and roots have different functions in resource uptake in the two species, which we mainly attributed to dissimilarities in carbon acquisition and growth traits (e.g., photosynthesis, relative growth rate, non-structural carbohydrates, malate), to water relation traits (e.g., water and osmotic potentials, relative water content, hydrenchyma thickness) and nutrient uptake (e.g., 15N-labelling). While the roots of A. aquilega did contribute to water and nutrient uptake, the roots of L. splendens were less important than the role played by the LATs in resource uptake. We also provide evidenced for a synergistic effect of combined watering of tank and root in the Bromelioideae species. These results call for a more complex interpretation of LATs vs. roots in resource uptake in bromeliads.

Nitrogen management influenced root length intensity of young olive trees

Nitrogen (N) status in olive trees is critical to develop several developmental mechanisms that control shoot, root and nutrient uptake capacity. The objective of this field study was to assess the effect of N level and form on root growth dynamics, shoot growth, leaf-level gas exchange [photosynthesis (Pn), transpiration (E), and stomatal conductance (gs)] and leaf nutrient content of young olive (Olea europaea cv. Arbequina) trees. Olive cuttings were planted in the field and grown for two years (2015, 2016). In both years, cuttings were subjected to 7 N treatments: control (no N), nitrate (NO3−) form applied as calcium nitrate (CN) at 20, 40 and 60 kg ha-1, and ammonium (NH4+) applied as urea at 20, 40 and 60 kg ha-1. Minirhizotron image analysis showed that the application of N significantly reduced root length intensity (La, mm cm-2) compared to control olives in both years. No significant difference was noticed between N forms for La in 2015. However, CN treatment had higher La than urea in April and June 2016. In addition, the overall mean of La across the study period (2015–2016) showed that La in the lower soil depths, 40–60 and 60–80 cm was significantly higher than those from the top layers, 0–20 and 20–40 cm. Unfertilized (control) cuttings had also higher tree height, stem diameter and branch number than olives that received 40 or 60 kg ha-1-N across the study period (2015-2016). In both years, leaf N% in control olives was above the N deficiency thresholds; i.e. 2.1% in 2015 and 2.57% in 2016. However, leaf mineral concentrations were inconsistent (P, Ca+2, Na, Zn, Fe, Cu) or not significant (Mn, S and B). In addition, no significant difference was noticed between treatments in gas exchange (Pn, gs and E). Overall, untreated-control young olive trees showed consistently higher La and shoot growth than N-treated trees (CN and urea) over the study period 2015-2016. Therefore, N application is not needed if leaf N levels are normal during the previous season. In fact, high rates of N in the soil during establishment of young olive trees can negatively affect root and shoot growth.

Nitrogen Nutrition of European Beech Is Maintained at Sufficient Water Supply in Mixed Beech-Fir Stands

Research highlights: Interaction effects of coniferous on deciduous species have been investigated before the background of climate change. Background and objectives: The cultivation of European beech (Fagus sylvatica L.) in mixed stands has currently received attention, since the future performance of beech in mid-European forest monocultures in a changing climate is under debate. We investigated water relations and nitrogen (N) nutrition of beech in monocultures and mixed with silver-fir (Abies alba Mill.) in the Black Forest at different environmental conditions, and in the Croatian Velebit at the southern distribution limit of beech, over a seasonal course at sufficient water availability. Material and methods: Water relations were analyzed via δ13C signatures, as integrative measures of water supply assuming that photosynthesis processes were not impaired. N nutrition was characterized by N partitioning between soluble N fractions and structural N. Results: In the relatively wet year 2016, water relations of beech leaves, fir needles and roots differed by season, but generally not between beech monocultures and mixed cultivation. At all sites, previous and current year fir needles revealed significantly lower total N contents over the entire season than beech leaves. Fir fine roots exhibited higher or similar amounts of total N compared to needles. Correlation analysis revealed a strong relationship of leaf and root δ13C signatures with soil parameters at the mixed beech stands, but not at pure beech stands. While glutamine (Gln) uptake capacity of beech roots was strongly related to soil N in the monoculture beech stands, arginine (Arg) uptake capacities of beech roots were strongly related to soil N in mixed stands. Conclusions: Leaf N contents indicated a facilitative effect of silver-fir on beech on sites where soil total N concentrations where low, but an indication of competition effect where it was high. This improvement could be partially attributed to protein contents, but not to differences in uptake capacity of an individual N source. From these results it is concluded that despite similar performance of beech trees at the three field sites investigated, the association with silver-fir mediated interactive effects between species association, climate and soil parameters even at sufficient water supply.

Sorbents can tailor nitrogen release from organic wastes to match the uptake capacity of crops

Delivering nutrients from mineral or organic fertilizers out of synchrony with crop uptake causes inefficiencies and pollution. We explore methodologies for evaluating sorbents as additives to organic agricultural wastes to retain nitrogen in an exchangeable form and deliver at rates that approximate the uptake capacity of roots. Focussing on ammonium (NH4+) as the main inorganic nitrogen form in the studied wastes (sugarcane mill mud, poultry litter), we tested geo-sorbents and biochar for their ability to retain NH4+. Sorption capacity was ranked palagonite < bentonite, biochar, vermiculite < chabazite, clinoptilolite (5.7 to 24.3 mg NH4+ g−1 sorbent). Sorbent-waste formulations were analysed for sorption capacity, leaching and fluxes of NH4+. Ammonium-sorption capacity broadly translated to sorbent-waste formulations with clinoptilolite conferring the strongest NH4+ attenuation (80%), and palagonite the lowest (7%). A 1:1 ratio of sorbent:waste achieved stronger sorption than a 0.5:1 ratio, and similar sorption as a 1:1.5 ratio. In line with these results, clinoptilolite-amended wastes had the lowest in situ NH4+ fluxes, which exceeded the NH4+ uptake capacity (Imax) of sugarcane and sorghum roots 9 to 84-fold, respectively. Less efficient sorbent-waste formulations and un-amended wastes exceeded Imax of crop roots up to 274-fold. Roots preferentially colonized stronger sorbent-waste formulations and avoided weaker ones, suggesting that lower NH4+ fluxes generate a more favourable growth environment. This study contributes methodologies to identify suitable sorbents to formulate organic wastes as next-generation fertilizers with view of a crop's nutrient physiology. Efficient re-purposing of wastes can improve nutrient use efficiency in agriculture and support the circular nutrient economy.