Affect Root Growth Research Articles

The effect of pinching and leaf defoliation on plant root architecture and bulb characteristics in lilium

In plants, leaves are the most important organs together with roots in terms of plant development. The effects of leaf defoliation and pinching on root architecture and bulb development were determined in lilies 'Vong' cultivar. For this purpose, leaf defoliation was determined as 0, 25%, 50%, 100%, and pinching was performed. Root length (cm), root surface area (cm2), root volume (cm3), root diameter (mm), number of tips, number of forks, and number of crossings in root architecture were measured. The effect of bulb properties was also determined in main bulb diameter (mm), bulb fresh weight (g), bulb dry weight (g), and bulbil diameter (mm). Leaf defoliation was found to affect root growth negatively. As the defoliation rate increased, the root architectural features decreased compared to the control. In contrast to leaf defoliation, the pinching application significantly increased root length (7568 cm), root surface area (9254 cm2), root volume (176 cm3), number of tips (8553), number of forks (40106), and number of crossings (7950). However, it had no effect on root diameter in two applications. In addition, while leaf defoliation decreased bulb characteristics, pinching application significantly increased bulb fresh weight (54.24 g), bulb dry weight (4.43 g), and bulb diameter (19.43 mm). It was also determined that the application that reduced the bulb fresh weight, bulb dry weight and bulb diameter the most was 100% leaf defoliation. As a result, it was found that pinching is the best method to ensure healthy root growth and bulb development, suggesting that it can be recommended for growing lilium bulbs.

Pachycereus pringlei seedling emergence and establishment under different lighting conditions

Cactus early life stages, especially in arid ecosystems, are typically the most vulnerable; seedlings face various abiotic and biotic filters to achieve survival and successful integration into their habitat. Thus, Pachycereus pringlei – endemic to Mexican Sonoran Desert – plays a crucial role in the arid areas of Baja California Sur, Mexico acting as a refuge and food source for wildlife. The present study evaluates P. pringlei emergence, survival, and seedling growth under different solar exposure (open and shaded areas) levels, both in greenhouse and natural conditions. The results indicated that natural conditions and moisture significantly influenced seedling emergence and survival. Lack of soil moisture led to compaction, which may have reduced porous spaces and restricted air and water circulation, thereby affecting root growth during the establishment phase. Conversely, the emerged seedling proportion under greenhouse shade was higher than in natural conditions. Additionally, these seedlings exhibited superior stem development, while those exposed to sunlight notably developed root systems. Low water potential was recorded, reaching down to -5.1 MPa for seedlings exposed to higher light levels. However, relative water content (RWC) values in tissues exceeded 70 %. No significant relationship was found between photosynthetic pigment concentration and different light conditions. Despite adapting cacti to xeric environments, the results suggest they may not be fully prepared to withstand prolonged drought episodes during the seedling stage. Nevertheless, some morphological traits, such as stem length, spines, and root area showed significant variations under different light conditions, facilitating photosynthesis light capture.

Rhizosphere development under alternate wetting and drying in puddled paddy rice

AbstractAlternate wetting and drying (AWD) irrigation can save large amounts of water in rice cultivation. By repeatedly wetting and drying the soil under AWD, accentuated pore structure of the rhizosphere compared to flooded rice may occur. This could affect root growth and resource capture, but to date the physical structure and behaviour of the rhizosphere of rice under AWD has not been explored. In a controlled glasshouse experiment, two different textured soils were used in split rhizotrunks to separate a root‐zone from bulk soil using mesh. To mimic a paddy field, the top of the rhizotrunk was filled with puddled soil and below the puddled layer there was a sieved soil layer. Root‐zone physical properties were measured using a combination of high resolution X‐ray CT imaging (pore structure), a miniaturised infiltrometer (hydrological) and a small indenter (mechanical). Soil under AWD irrigation had 46% greater macroporosity and 20% more pore connectivity compared to continuous flooding (CF). Compared to the bulk soil, root‐zone soil under AWD or CF had greater macroporosity, water sorptivity and mechanical hardness. In the root‐zone, AWD compared to CF increased the rate of water absorption by around 36%, but did not affect mechanical hardness. Our results suggest AWD interacting with rice roots could promote more effective water transmission through a more stable, larger and better‐connected pore system. The results of this study also suggest that soil physical changes by AWD could improve the utilization of resources in a rice production system.

Grassland management intensity determines root development, soil structure, and their interrelationship: Results of a regional study of Leptosols in the Swabian Alps

AbstractBackgroundSoil structure is a key indicator of the functioning of soil processes in grasslands, which is influenced by site conditions and management.MethodsIn this study, we investigated soil structure and its relationship with root growth in 31 Leptosols under different grassland management intensities using X‐ray microcomputed tomography. A close relationship between land use intensity, soil structure, and root growth was observed.ResultsOur results show that land use type affects root development and soil structure. Pastures had more developed roots and more structured soils than meadows and mown pastures. However, all pastures were unfertilized, while meadows and mown pastures had both fertilized and unfertilized plots. Although no significant differences were found in the unfertilized plots, sample size was limited. In particular, fertilization negatively affected root growth and soil structure, resulting in significant differences between fertilized and unfertilized grasslands. Mowing frequency also had an effect on soil physics, but to a much lesser extent than fertilization.ConclusionsIncreased land use intensity, characterized by increased fertilization and more frequent mowing, reduces root growth and adversely affects soil structure. Therefore, X‐ray microcomputed tomography is a suitable method to investigate the relationship between soil structure and roots in the soil.

Physiological and proteomic characterization revealed the response mechanisms underlying aluminium tolerance in lentil (Lens culinaris Medikus).

Aluminium (Al) toxicity causes major plant distress, affecting root growth, nutrient uptake and, ultimately, agricultural productivity. Lentil, which is a cheap source of vegetarian protein, is recognized to be sensitive to Al toxicity. Therefore, it is important to dissect the physiological and molecular mechanisms of Al tolerance in lentil. To understand the physiological system and proteome composition underlying Al tolerance, two genotypes [L-4602 (Al-tolerant) and BM-4 (Al-sensitive)] were studied at the seedling stage. L-4602 maintained a significantly higher root tolerance index and malate secretion with reduced Al accumulation than BM-4. Also, label-free proteomic analysis using ultra-performance liquid chromatography-tandem mass spectrometer exhibited significant regulation of Al-responsive proteins associated with antioxidants, signal transduction, calcium homeostasis, and regulation of glycolysis in L-4602 as compared to BM-4. Functional annotation suggested that transporter proteins (transmembrane protein, adenosine triphosphate-binding cassette transport-related protein and multi drug resistance protein), antioxidants associated proteins (nicotinamide adenine dinucleotide dependent oxidoreductase, oxidoreductase molybdopterin binding protein & peroxidases), kinases (calmodulin-domain kinase & protein kinase), and carbohydrate metabolism associated proteins (dihydrolipoamide acetyltransferase) were found to be abundant in tolerant genotype providing protection against Al toxicity. Overall, the root proteome uncovered in this study at seedling stage, along with the physiological parameters measured, allow a greater understanding of Al tolerance mechanism in lentil, thereby assisting in future crop improvement programmes.

The trade-off between root growth redundancy and premature senescence under different straw returning modes affects boll formation and seedcotton yield

The indeterminate growth habit of cotton (Gossypium hirsutum L.) makes a coordinated rootshoot relationship critical for increasing yield, which requires comprehensive consideration of root growth redundancy and premature senescence. Although recent evidence suggests that straw management affects root growth and thus seedcotton yield, there is limited documentation on the dynamics of root physiological activity and the rootshoot relationship of cotton under different straw returning modes. The present study compared four treatments: straw removal (CK), straw mulching (SM), straw incorporation (SI), and strawderived biochar incorporation (SBI) in an 8year field experiment. The growth dynamics of roots, shoots and reproductive organs, root physiological activity and seedcotton yield were investigated. The results showed that longterm straw application significantly enhanced seedcotton yield, but the effect varied significantly with straw returning modes. The seedcotton yield increased by 30.5%, 17.8% and 1.8% under SBI, SI and SM respectively in the 8th year of straw management, compared to CK. SBI and SI significantly enhanced the biomass of cotton roots and shoots while had higher growth rate of shoots relative to roots from peak squaring stage to peak bollsetting stage. This reduced root growth redundancy and increased the boll loading and boll capacity of root system. Besides, SBI increased the root activity, soluble protein content and antioxidant enzyme activities, and reduced the root malondialdehyde content from peak bollsetting stage to boll opening stage. These resulted in the greatest increase in boll number (53.862.1%) and boll biomass (39.480.4%) at the boll opening stage under SBI compared to CK. Overall, strawderived biochar improved the boll retention capacity of cotton roots by balancing the growth redundancy and premature senescence of the root system, and was a more suitable straw returning strategy to promote boll formation and increase cotton yield.

Temporary growth cessation of wheat roots following defoliation

Background and aimsDefoliation triggers the remobilisation of root reserves to generate new leaves which can affect root growth until the shoot resumes net assimilation. However, the duration of root growth cessation and its impact on resource uptake potential is uncertain.MethodsWinter wheat was established in a 4 m high outdoor rhizobox facility equipped with imaging panels, sensors, and access points for tracer-labelling. The wheat was defoliated in autumn at early tillering and roots were imaged at a high-time resolution and analyzed by deep learning segmentation. The water and nitrogen (N) uptake were measured using time-domain reflectometer (TDR) sensors and 2H and 15N isotopes.ResultsRoot penetration of wheat paused for 269 °C days (20 days) following defoliation after which it resumed at a similar rate to un-defoliated plants (1.8 mm °C days−1). This caused a substantial decrease in root density with an associated reduction in water and N uptake at maturity, especially from deeper soil layers (>2 m).ConclusionsOur results have significant implications for managing the grazing of dual-purpose crops to balance the interplay between canopy removal and the capacity of deep roots to provide water and N for yield recovery.

Using biochar for environmental recovery and boosting the yield of valuable non-food crops: The case of hemp in a soil contaminated by potentially toxic elements (PTEs)

Hemp (Cannabis sativa L.) is known to tolerate high concentrations of soil contaminants which however can limit its biomass yield. On the other hand, organic-based amendments such as biochar can immobilize soil contaminants and assist hemp growth in soils contaminated by potentially toxic elements (PTEs), allowing for environmental recovery and income generation, e.g. due to green energy production from plant biomass. The aim of this study was therefore to evaluate the suitability of a softwood-derived biochar to enhance hemp growth and promote the assisted phytoremediation of a PTE-contaminated soil (i.e., Sb 2175 mg kg−1; Zn 3149 mg kg−1; Pb 403 mg kg−1; and Cd 12 mg kg−1). Adding 3% (w/w) biochar to soil favoured the reduction of soluble and exchangeable PTEs, decreased soil dehydrogenase activity (by ∼2.08-fold), and increased alkaline phosphomonoesterase and urease activities, basal respiration and soil microbial carbon (by ∼1.18-, 1.22-, 1.22-, and 1.66-fold, respectively). Biochar increased the abundance of selected soil culturable microorganisms, while amplicon sequencing analysis showed a positive biochar impact on α-diversity and the induction of structural changes on soil bacterial community structure. Biochar did not affect root growth of hemp but significantly increased its aboveground biomass by ∼1.67-fold for shoots, and by ∼2-fold for both seed number and weight. Biochar increased the PTEs phytostabilisation potential of hemp with respect to Cd, Pb and Zn, and also stimulated hemp phytoextracting capacity with respect to Sb. Overall, the results showed that biochar can boost hemp yield and its phytoremediation effectiveness in soils contaminated by PTEs providing valuable biomass that can generate profit in economic, environmental and sustainability terms.

Quantifying carbon pool in ex-mining lake-converted constructed wetlands of Paya Indah Wetlands, Selangor, Malaysia.

Ex-mining lake-converted constructed wetlands play a significant role in the carbon cycle, offering a great potential to sequester carbon and mitigate climate change and global warming. Investigating the quantity of carbon storage capacity of ex-mining lake-converted constructed wetlands provides information and justification for restoration and conservation efforts. The present study aims to quantify the carbon pool of the ex-mining lake-converted constructed wetlands and characterise the physicochemical properties of the soil and sediment. Pearson's correlation and a one-way ANOVA were performed to compare the different sampling stations at Paya Indah Wetland, Selangor, Malaysia. An analysis of 23years of ex-mining lake-converted constructed wetlands of Paya Indah Wetlands, Selangor, Malaysia, revealed that the estimated total carbon pool in soil and sediment accumulated to 1553.11 Mg C ha-1 (equivalent to 5700 Mg CO2 ha-1), which translates to an annual carbon sink capacity of around 67.5 Mg C ha-1 year-1. The characterisation showed that the texture of all soil samples was dominated by silt, whereas sediments exhibited texture heterogeneity. Although the pH of the soil and sediment was both acidic, the bulk density was still optimal for plant growth and did not affect root growth. FT-IR and WDXRF results supported that besides the accumulation and degradation of organic substances, which increase the soil and sediment carbon content, mineral carbonation is a mechanism by which soil and sediment can store carbon. Therefore, this study indicates that the ex-mining lake-converted constructed wetlands of Paya Indah Wetlands, Selangor, Malaysia have a significant carbon storage potential.

Ectopic assembly of an auxin efflux control machinery shifts developmental trajectories.

Polar auxin transport in the Arabidopsis (Arabidopsis thaliana) root tip maintains high auxin levels around the stem cell niche that gradually decrease in dividing cells but increase again once they transition toward differentiation. Protophloem differentiates earlier than other proximal tissues and employs a unique auxin "canalization" machinery that is thought to balance auxin efflux with retention. It consists of a proposed activator of PIN-FORMED (PIN) auxin efflux carriers, the cAMP-, cGMP- and Calcium-dependent (AGC) kinase PROTEIN KINASE ASSOCIATED WITH BRX (PAX); its inhibitor, BREVIS RADIX (BRX); and PHOSPHATIDYLINOSITOL-4-PHOSPHATE-5-KINASE (PIP5K) enzymes, which promote polar PAX and BRX localization. Because of a dynamic PAX-BRX-PIP5K interplay, the net cellular output of this machinery remains unclear. In this study, we deciphered the dosage-sensitive regulatory interactions among PAX, BRX, and PIP5K by their ectopic expression in developing xylem vessels. The data suggest that the dominant collective output of the PAX-BRX-PIP5K module is a localized reduction in PIN abundance. This requires PAX-stimulated clathrin-mediated PIN endocytosis upon site-specific phosphorylation, which distinguishes PAX from other AGC kinases. An ectopic assembly of the PAX-BRX-PIP5K module is sufficient to cause cellular auxin retention and affects root growth vigor by accelerating the trajectory of xylem vessel development. Our data thus provide direct evidence that local manipulation of auxin efflux alters the timing of cellular differentiation in the root.

The effects of soil compaction on wheat seedling root growth are specific to soil texture and soil moisture status

Soil structure is a crucial soil physical property that determines a soil's ability to support the growth and development of plants. Soil compaction modifies soil structure by reducing pore space between soil particles thereby leading to a denser soil fabric. This often limits root growth by increasing soil strength and penetration resistance requiring roots to increase the energy needed to elongate and explore deeper soil. Apart from soil compaction, soil moisture also plays an important role in determining how resistant soil is to root penetration. An understanding of how the synergy of both compaction and moisture content affect root growth is essential to improving plant productivity. We used wheat (Triticum aestivum) seedlings to investigate the differences in root architectural properties using X-ray Computed Tomography imaging under three different compaction levels (1.3, 1.5 and 1.7 Mg m−3) maintained at two different water contents (100% and 70% of field capacity). This was performed on soils of two different textures, a sandy loam and a sandy clay loam. Soil compaction to 1.7 g cm−3 significantly reduced root length, volume and surface area compared to lower compaction levels. Increased soil compaction also resulted in increased root growth angle in the sandy clay loam. Compaction reduced gas diffusivity in both soils (as determined by modelling). Soil moisture on the other hand had a significant impact on average root diameter; plants grown at 100% of field capacity had a higher average root diameter than those at 70% field capacity. Compaction up to 1.7 Mg m−3 adversely effected wheat root growth in both soil textures regardless of moisture content.

The primacy of temporal dynamics in driving spatial self-organization of soil iron redox patterns.

This study investigates mechanisms that generate regularly spaced iron-rich bands in upland soils. These striking features appear in soils worldwide, but beyond a generalized association with changing redox, their genesis is yet to be explained. Upland soils exhibit significant redox fluctuations driven by rainfall, groundwater changes, or irrigation. Pattern formation in such systems provides an opportunity to investigate the temporal aspects of spatial self-organization, which have been heretofore understudied. By comparing multiple alternative mechanisms, we found that regular iron banding in upland soils is explained by coupling two sets of scale-dependent feedbacks, the general principle of Turing morphogenesis. First, clay dispersion and coagulation in iron redox fluctuations amplify soil Fe(III) aggregation and crystal growth to a level that negatively affects root growth. Second, the activation of this negative root response to highly crystalline Fe(III) leads to the formation of rhythmic iron bands. In forming iron bands, environmental variability plays a critical role. It creates alternating anoxic and oxic conditions for required pattern-forming processes to occur in distinctly separated times and determines durations of anoxic and oxic episodes, thereby controlling relative rates of processes accompanying oxidation and reduction reactions. As Turing morphogenesis requires ratios of certain process rates to be within a specific range, environmental variability thus modifies the likelihood that pattern formation will occur. Projected changes of climatic regime could significantly alter many spatially self-organized systems, as well as the ecological functioning associated with the striking patterns they present. This temporal dimension of pattern formation merits close attention in the future.

Light pre-conditioning at the seedling stage affected root growth behavior and enhanced the thermotolerance of Petunia × hybrida

An investigation studied the impact of spectral composition on plant responses to heat stress. Petunia × hybrida seedlings were grown under nine different light qualities, including the modifying and constant compositions of blue and red LEDs light, as well as Fluorescent and white LED lamps. After 28 days, the seedlings were exposed to hyperthermia (40 °C / 35 °C, 4 days). The results showed that the highest survival rate (100 %), and the lowest leaf chlorotic area (14 %) were observed among seedlings grown under modifying spectral compositions with a gradual increase in red light, which also showed the highest change rate of increased Chl a/ b ratio (262 %) and lowest change rate of increased total Chl/ Car ratio (45 %). Furthermore, seedlings grown under a gradual increase in red light showed the highest relative water content (82 %) and the lowest change rate of root water content (1.2 %). Moreover, the highest proline and lignin contents, along with the lowest electrolyte leakage, 7.22 µg g−1 FW, 104 mg g−1 FW, and 25 %, respectively, were observed in seedlings exposed to a gradual increase in red light after heat stress compared to other lighting treatments. Also, after heat stress, seedlings grown under a gradual increase in red light showed the highest contents of studied enzymatic antioxidants. Our investigation highlighted a link between spectral composition during the seedling stage and heat stress tolerance of examined plants. This method can potentially prepare plant material during the propagation stage against extreme temperatures.

Effects of Magnesium Imbalance on Root Growth and Nutrient Absorption in Different Genotypes of Vegetable Crops.

Magnesium (Mg) plays a crucial role in crop growth, but how Mg supply level affects root growth and nutrient absorption in vegetable crops with different genotypes has not been sufficiently investigated. In this study, the responses of tomato (Solanum lycopersicum L.) and cucumber (Cucumis sativus L.) crops to different levels of Mg supply were explored. Four levels of Mg treatment (i.e., 0.2, 1.0, 2.0, 3.0 mmol/L) were applied under hydroponic conditions, denoted as Mg0.2, Mg1, Mg2, and Mg3, respectively. The results showed that with increasing Mg levels, the plant biomass, root growth, and nutrient accumulation in both vegetable crops all increased until reaching their maximum values under the Mg2 treatment and then decreased. The total biomass per tomato plant of Mg2 treatment was 30.9%, 14.0%, and 14.0% higher than that of Mg0.2, Mg1, and Mg3 treatments, respectively, and greater increases were observed in cucumber plant biomass (by 54.3%, 17.4%, and 19.9%, respectively). Compared with the Mg0.2 treatment, the potassium (K) and calcium (Ca) contents in various plant parts of both crops remarkably decreased under the Mg3 treatment. This change was accompanied by prominently increased Mg contents in various plant parts and para-hydroxybenzoic acid and oxalic acid contents in root exudates. Irrespective of Mg level, plant biomass, root growth, nutrient accumulation, and root exudation of organic acids were all higher in tomato plants than in cucumber plants. Our findings indicate that excessive Mg supply promotes the roots to exude phenolic acids and hinders the plants from absorbing K and Ca in different genotypes of vegetable crops despite no effect on Mg absorption. A nutritional deficiency of Mg stimulates root exudation of organic acids and increases the types of exuded organic acids, which could facilitate plant adaption to Mg stress. In terms of root growth and nutrient absorption, tomato plants outperform cucumber plants under low and medium Mg levels, but the latter crop is more tolerant to Mg excess.

The Effect of Soaking Root Fertilizer on Promoting the Seedling Early Growth and Root Development of Eucalyptus urograndis

We examined the feasibility of applying soaking root fertilizer to Eucalyptus urograndis seedlings by dipping the roots, and the effectiveness of the method for improving the overall growth quality of the seedlings by affecting root growth. The seedlings of E. urograndis in the Southern National Forest Seedling Demonstration Base in China were dipped with seven kinds of soaking root fertilizer formulas, while another group of clear water was set as a control. We regularly investigated the relationship between root traits and other seedling traits, and the formulas conducive to the high-quality growth of seedlings in one month and two months were screened by principal component analysis (PCA). The feasibility of applying soaking root fertilizer by dipping the roots was analyzed by comparing the difference between the formula and the control. The F2 formula had the best promoting effect on the growth and biomass of seedlings and the highest ground diameter within one month. The biomass, cumulative height growth, and average crown width were also the highest in the two months, but the decreasing growth height in F2 was also obvious, along with reduced photosynthesis and root morphology. The F8 and F4 formulas as compound fertilizers showed the potential of a high growth rate and high quality. The seedlings on which they were all applied had an excellent photosynthetic capacity and a well-developed root system. A correlation analysis showed that root traits were significantly correlated with some aboveground indices of seedlings (growth, biomass and nutrients, etc.), among which the root K concentration was very significantly correlated with photosynthetic capacity, and the root P was very significantly correlated with seedling biomass. Dipping roots mainly promoted the uptake of P and K nutrients by roots, which had a positive effect on seedling photosynthesis and the root system, and thus improved the growth increment and growth quality of seedlings. A principal component analysis showed that dipping roots significantly promoted the growth traits of seedlings, and the best-performing formula for dipping roots was F8 at one month of growth. F4 was the best choice for growth at two months. F4 showed excellent performance in all trait indices and was the only treatment where an increase in the rhizome-to-stem ratio occurred, indicating that the nutrient distribution of F4 seedlings was uniform and efficient, which compensated for the deficiency of the follow-up fertility of the quick-acting complex fertilizer. The scientific formula of soaking root fertilizer can be economically applied by dipping roots to synchronously promote early growth and quality of seedlings, which can provide a theoretical basis for the early large-scale cultivation of E. urograndis and other plants.

Freeze-thaw process induced by increased precipitation affects root growth of alpine steppe on the Tibetan Plateau

Freeze-thaw process induced by increased precipitation affects root growth of alpine steppe on the Tibetan Plateau

Combinatorial Effects of Glycine and Inorganic Nitrogen on Root Growth and Nitrogen Nutrition in Maize (Zea mays L.)

Organic and inorganic nitrogen play important roles in plant nitrogen nutrition. However, how the coapplication of organic and inorganic nitrogen affects root growth, plant nitrogen metabolism, and soil nitrogen content is still unclear. Plant shoot and root growth, nitrogen uptake and metabolism, and soil nitrogen content were studied in maize (Zea mays L.) through pot experiments with different nitrogen treatments, including NH4+ -N (Amm), NO3− -N (Nit), NH4+ -N + NO3− -N (Amm + Nit), NH4+ -N + NO3− -N + glutamate-N (Amm + Nit + Glu), and NH4+ -N + NO3− -N + glycine-N (Amm + Nit + Gly). The results show that the shoot nitrogen uptake of maize treated with Amm + Nit + Gly was the highest among all the nitrogen treatments. In addition, the coapplication of glycine and inorganic nitrogen increased glutamine synthetase (GS) activity in the maize leaves, promoted nitrogen metabolism levels, and was conducive to the accumulation of amino acids and soluble protein in leaves. Compared with inorganic nitrogen, glycine combined with inorganic nitrogen increased the total root length and root surface area. A correlation analysis showed that total root length and root surface area had a significant positive effect on nitrogen uptake. When ammonium, nitrate, and glycine were applied together, the content of inorganic nitrogen and total nitrogen in soil was higher than that for other inorganic nitrogen treatments. Therefore, we conclude that glycine combined with inorganic nitrogen can increase soil nitrogen content, promote maize root growth, and thus facilitate nitrogen uptake and metabolism.

L-DOPA induces iron accumulation in roots of Ipomoea aquatica and Arabidopsis thaliana in a pH-dependent manner

BackgroundIron deficiency is the leading cause of anemia worldwide, particularly in countries with predominant plant-based diets. Plants constitute the main source of dietary iron. Increasing their iron concentration could reduce the occurrence of anemia. The water spinach Ipomoea aquatica is consumed as a vegetable throughout Asia and tolerates high iron concentrations making it an attractive candidate for iron biofortification. L-DOPA is an allelopathic molecule secreted by some legumes. L-DOPA can trigger the expression of Fe deficiency-inducible genes, and could potentially be used as a biostimulant to increase Fe concentration.ResultsL-DOPA significantly affected root growth of water spinach, and triggered a massive accumulation of Fe in roots. Both effects were exacerbated when L-DOPA was dissolved in KOH, which is surprising given that L-DOPA is less stable at high pH. To check whether a higher pH could indeed increase the bioactivity of L-DOPA, we used Arabidopsis thaliana, which grows at lower pH than water spinach, and subjected the plants to L-DOPA treatments at pH 5.5 and pH 6.0, which are both within the optimal range for Arabidopsis nutrition. At pH 6.0, the root growth of Arabidopsis was more strongly inhibited than at pH 5.5. We found that at higher pH, L-DOPA oxidizes to form a melanin precipitate.ConclusionsWe concluded that the oxidation of L-DOPA that we observed upon solubilization in KOH, or in nutrient solutions at slightly higher pH produces melanin-related molecules that are more potent than L-DOPA itself to trigger the primary root growth inhibition, Fe uptake and root Fe accumulation in water spinach and Arabidopsis.

Effects of Root Growth of Deep and Shallow Rooting Rice Cultivars in Compacted Paddy Soils on Subsequent Rice Growth

Rice is often grown as multiple seasons in one year, alternating between flooded and upland systems. A major constraint, introduced from the flooded system, is a plough pan that may decrease rooting depth and productivity of follow-on upland rice. Roots penetrating the plough pan under flooded rice system can leave a legacy of weaker root growth pathways. Deeper rooting rice cultivars could have a bigger impact, but no direct evidence is available. To explore whether a deep rather than a shallow rooting rice cultivar grown in a flooded cropping cycle benefited deeper root growth of follow-on rice in an upland, reduced tillage cropping cycle, a simulated flooded paddy in greenhouse was planted with deep (Black Gora) and shallow (IR64) rooting cultivars and a plant-free control. Artificial plough pans were made in between the topsoil and subsoil to form different treatments with no plough pan (0.35 MPa), soft plough pan (1.03 MPa) and hard plough pan (1.70 MPa). After harvest of this ‘first season’ rice, the soil was drained and undisturbed to simulate zero-tillage upland and planted rice cultivar BRRI Dhan 28. The overall root length density (RLD), root surface area, the numbers of root tips and branching of BRRI Dhan 28 did not vary between plough pan and no plough pan treatments. Compared with the shallow rooting rice genotype, the deep rooting rice genotype as ‘first season’ crop produced 19% greater RLD, 34% greater surface area and 29% more branching of BRRI Dhan 28 in the subsoil. In the topsoil, however, BRRI Dhan 28 had 28% greater RLD, 35% greater surface area and 43% more branching for the shallow rather than deep rooting genotype planted in the ‘first season’. The results suggested that rice cultivar selection for a paddy cycle affects root growth of a follow-on rice crop grown under no-till, with benefits to subsoil access from deep rooting cultivars and topsoil proliferation for shallow rooting cultivars.

Hybrid performance evaluation and genome-wide association analysis of root system architecture in a maize association population.

The genetic architecture of RSA traits was dissected by GWAS and coexpression networks analysis in a maize association population. Root system architecture (RSA) is a crucial determinant of water and nutrient uptake efficiency in crops. However, the maize genetic architecture of RSA is still poorly understood due to the challenges in quantifying root traits and the lack of dense molecular markers. Here, an association mapping panel including 356 inbred lines were crossed with a common tester, Zheng58, and the test crosses were phenotyped for 12 RSA traits in three locations. We observed a 1.3 ~ sixfold phenotypic variation for measured RSA in the association panel. The association panel consisted of four subpopulations, non-stiff stalk (NSS) lines, stiff stalk (SS), tropical/subtropical (TST), and mixed. Zheng58 × TST has a 2.1% higher crown root number (CRN) and 8.6% less brace root number (BRN) than Zheng58 × NSS and Zheng58 × SS, respectively. Using a genome-wide association study (GWAS) with 1.25 million SNPs and correction for population structure, 191 significant SNPs were identified for root traits. Ninety (47%) of the significant SNPs showed positive allelic effects, and 101 (53%) showed negative effects. Each locus could explain 0.39% to 11.8% of phenotypic variation. By integrating GWAS results and comparing coexpression networks, 26 high-priority candidate genes were identified. Gene GRMZM2G377215, which belongs to the COBRA-like gene family, affected root growth and development. Gene GRMZM2G468657 encodes the aspartic proteinase nepenthesin-1, related to root development and N-deficient response. Collectively, our research provides progress in the genetic dissection of root system architecture. These findings present the further possibility for the genetic improvement of root traits in maize.