Lateral Root Length Research Articles

Genome-wide identification of nitrate transporter genes from Spirodela polyrhiza and characterization of SpNRT1.1 function in plant development

Nitrate transporter (NRT) genes that participate in nitrate transport and distribution are indispensable for plant growth, development, and stress tolerance. Spirodela polyrhiza has the smallest genome among monocotyledon plants, and it has strong nitrate absorbance and phytoremediation abilities. However, the evolutionary history, expression patterns, and functions of the NRT gene family in S. polyrhiza are not well understood. Here, we identified 29 NRT members in the S. polyrhiza genome. Gene structure and phylogeny analyses showed that S. polyrhiza nitrate transporter (SpNRTs) genes were divided into eight clades without gene expansion compared with that in Arabidopsis. Transcriptomic analysis showed that SpNRT genes have spatiotemporal expression patterns and respond to abiotic stress. Functional analysis revealed that in S. polyrhiza, SpNRT1.1 expression was strongly induced by treatment with nitrate and ammonium. Overexpression of SpNRT1.1 significantly repressed primary root length, and the number and total length of lateral roots. This was more pronounced in high ammonium concentration medium. Overexpressed SpNRT1.1 in Arabidopsis significantly improved biomass and delayed flowering time, indicating that the nitrate transport ability of SpNRT1.1 differs from AtNRT1.1. In conclusion, our results provide valuable information about the evolution of the NRT family in higher plants and the function of SpNRT1.1.

Chemical pregerminative promoters in Zea mays L. seed

Objective: Plant life begins at germination. Stimulating germination with chemical methods can be advantageous. The pregerminative treatment of four promoters was determined in two maize genotypes (G1, G2). Design/methodology/approach: Sixty seeds per Petri dish were used as experimental unit with three repetitions, organized in a completely randomized 2×4 factorial design. Two factors were taken into consideration: A) Genotypes (G1, G2); and B) four pregerminative promoters. The genotypes were Antelope G1 and yellow Antelope G2. Meanwhile, the pregerminative promoters were salicylic acid (‎C7H6O3) (SA), citrulline (C6H13N3O3) (CI), humic substances derived from leonardite (HS), and tap water (TW), in 1000-ppm concentrations. The following variables were evaluated: germination percentage (GP)/days-1, radicle diameter (RD), radicle length (RL), and number of lateral seminal roots (NSR). An analysis of variance and Tukey tests (α £ 0.05) were performed. Results: The germination promoters were highly significant in both genotypes, as well as during the promoter-genotype interaction. G1 and G2 means showed a higher growth and development for humic substances (HS) during germination in the NSR. Study Limitations/Implications: Germination can be inhibited, if the promoters are overweighted. Findings/Conclusions: The best genotype and germination promoter (G2) had a 94% effectiveness and HS at 1000 ppm. CI and SA registered the lowest GP.

Efficacy of amended vermicompost for bio-control of root knot nematode (RKN) Meloidogyne incognita infesting tomato in Egypt

Root-knot nematodes (RKNs) ( Meloidogyne spp) is the most economically destructive species. A pot experiment was conducted to assess the suppressing potential of three vermicompost types of different plant residues origin on (RKNs) ( Meloidogyne incognita ) in tomato cultivar by inoculation in prepared soil. Three vermicompost types CD (Cow dung) alone; CD mixed with either Taro Leaves (TL) or Saw Dust (SD) as carbonaceous sources were prepared for this study. Results revealed an overall significant increase in RKNs infected plants growth parameters in the vermicompost (SD + CD and TL+ CD) inoculated soil. Whereas, markedly increments were observed in root, shoot length and number of lateral roots besides their marvelous effect on controlling the RKN infection and blocking it to be restricted to the outer layer of vascular bundle. Our findings elucidated that different plant wastes origin vermicompost types have noticeable effects on RKNs infected tomato plants. The applied vermicompost (CD with either SD or TL) is serving not only as bio-organic fertilizer but also as effective bio-controlling treatment for root-knot nematodes and has no negative effect on the environment. • Emphasize the critical damage the caused by root-knots for crops especial tomato. • Nematocide causes a negative impacts on crops and environment. • There are strong needs to move toward organic practices to protect environment. • Bio-control considered an import an approach toward an organic production. • Vermicompost has the ability to be an effective bio-control for several pathogenic also, using different crops residues may improve efficiency of vermicompost in combats pathogen.

Local nitrogen application increases maize post-silking nitrogen uptake of responsive genotypes via enhanced deep root growth

Nitrogen (N) is unevenly distributed throughout the soil and plant roots proliferate in N-rich soil patches. However, the relationship between the root response to localized N supply and maize N uptake efficiency among different genotypes is unclear. In this study, four maize varieties were evaluated to explore genotypic differences in the root response to local N application in relation to N uptake. A split-root system was established for hydroponically-grown plants and two methods of local N application (local banding and local dotting) were examined in the field. Genotypic differences in the root length response to N were highly correlated between the hydroponic and field conditions (r>0.99). Genotypes showing high response to N, ZD958, XY335 and XF32D22, showed 50–63% longer lateral root length and 36–53% greater root biomass in N-rich regions under hydroponic conditions, while the LY13 genotype did not respond to N. Under field conditions, the root length of the high-response genotypes was found to increase by 66–75% at 40–60 cm soil depth, while LY13 showed smaller changes in root length. In addition, local N application increased N uptake at the post-silking stage by 16–88% in the high-response genotypes and increased the grain yield of ZD958 by 10–12%. Moreover, yield was positively correlated with root length at 40–60 cm soil depth (r=0.39). We conclude that local fertilization should be used for high-response genotypes, which can be rapidly identified at the seedling stage, and selection for “local-N responsive roots” can be a promising trait in maize breeding for high nitrogen uptake efficiency.

Maize varieties and their root trait variation mediate the development of rhizosphere arthropod diversity

While ecological roles of rhizosphere arthropods are well documented, little is known about the relationship between the development of plant roots and soil arthropod communities in agroecosystems. In this study, we investigated the effects of maize varieties and their root traits on the diversity and community composition of soil arthropods over time. Soil arthropods and root traits were evaluated before planting and at 30 and 60 days after planting in four maize varieties with different root growth angles and lateral root branching. Arthropod diversity declined from day 0 to 30 but recovered by day 60 with the development of maize roots. Two maize varieties (Nei 542018 and Nei 542022) exhibited lower brace and crown root angles, and arthropod taxon richness was greater in these two varieties than in others. The highest abundance of detritivores and predators was found in one of the maize varieties (Nei 542018) which, in addition to lower root angle, attained greater root diameter and lateral root branching and length. Redundancy analysis indicated that soil arthropod composition was correlated with crown root angle. Our findings highlight the importance of root traits, especially the angle of the roots, to enhance arthropod biodiversity in the rhizosphere ecosystem.

Zinc Nutrition for Improving the Growth and Yield of Barnyard Millet (Echinochola frumantacea L.)

Aims: To evaluate the effect of various levels and methods of zinc fertilization in improving the growth and yield of barnyard millet at different growth stages.
 Study Design: Randomized Block Design (RBD) with three replications.
 Place and Duration of Study: A field experiment was conducted in the farmer’s field at Pasur village, Coimbatore district from January to April, 2022.
 Methodology: A field experiment was conducted with barnyard millet (Echinochloa frumentacea L.) var. MDU 1 by using different levels of ZnSO4 at 5, 10, 15, 20 and 25 kg ha-1 as basal soil application and foliar spraying of 0.25, 0.50 & 0.75% twice along with soil test based NPK as control in Randomized Block Design with three replications. The growth and yield parameters such as plant height, SPAD index, root length, lateral root length, root volume, no. of tillers, panicle length, panicle weight, 1000 grain weight, grain and straw yield were recorded as per standard protocols.
 Results: Application of soil test based NPK + 20 kg ZnSO4 ha-1 performed better in increasing the plant height (157.0 cm), SPAD index (46.3), root length (21.1 cm), lateral root length (16.3 cm), root volume (3.80 cc) and yield attributes like number of tillers (5.06), panicle length (17.6 cm), panicle weight (29.2 g) and 1000 seed weight (3.89g) of barnyard millet. Higher grain (2606 kg ha-1) and straw yield (3411 kg ha-1) was also registered with the addition of soil test based NPK+20 kg ZnSO4 ha-1 which was 27.1% increase over NPK.
 Conclusion: Basal soil application of soil test based NPK + 20 kg ZnSO4 ha‑1 was found optimal and economical for improving the growth and yield of barnyard millet variety MDU 1.

Competition between Rice and Weedy Rice under Different Water Regimes

The rainfed lowland (RFL) rice ecosystem is prone to drought stress and high weed infestation, including weedy rice (WR), which often negatively affects the yield. This study examined the competitive ability of rice and WR under mixed culture and drought stress. Two rice genotypes (drought-susceptible IR64 and drought-tolerant INL73) and a WR were grown in root boxes with soil under mono (rice or WR only) or mixed (rice/WR) cultures and subjected to either continuously waterlogged (CWL) or progressive drought (PDR) conditions during the early vegetative stage. Under PDR, SDW in all planting cultures was reduced relative to their CWL counterparts. The WR in mixed culture had higher SDW than its monoculture counterpart, regardless of water treatments. SDW in mixed cultures under PDR was not affected in IR64, reduced in INL73, and increased in WR relative to their monocultures. Under PDR, water use (WU) was higher in INL73/ WR than in IR64/WR mixed culture. Between two mixed cultures, WR mixed with INL73 had higher SDW than when mixed with IR64. The differences in stomatal conductance between INL73 and WR under mixed culture were attributed to the greater increase in total lateral root length of the latter than the former genotype under PDR. Overall, the results showed that WR had greater competitive ability than rice under mixed cultures, especially with a drought-tolerant rice variety. This calls for careful planning of cultivar adoption in rainfed systems where WR is a problem.

Effect of Biochar Application to Fertile Soil on Tomato Crop Production under Saline Irrigation Regime

Biochar application is a promising sustainable strategy for enhancing soil properties thus crop production. However, biochar application to soil certainly alters its biological and physical properties, and could require extra costs. Therefore, biochar suitability to agroecosystems must be proactively estimated. The advantage of biochar addition to poor fertile or weathered soils has been well studies, however, its feasibility to fertile soil under low quality (saline) irrigation water was not frequently studied. Consequently, this work investigates the hypothesis of whether the application of biochar at a rate of 4.8 tons/ha to fertile soil (Nile Valley, Giza, Egypt) would ameliorate the negative effects of saline irrigation regime (3000 ppm) on tomato crop and soil. The results of two seasons experiments showed that saline irrigation significantly reduced tomato crop yield by an average reduction ratio of 51%, and biochar addition could not compensate such reduction. Furthermore, biochar did not reduce accumulated Na+ in fruits or roots. Tomato fruits produced from biochar-added soil were lower in TSS levels (41.7% reduction ratio) yet larger in diameter by approximately 1.5-fold increase. Interestingly, biochar addition into soil greatly promotes the length of stem-borne lateral roots and elevates the expression of LeNR (encodes nitrate reductase enzyme) in leaves yet under fresh irrigation regime. For soil properties, biochar application enhanced the soil properties under either saline or fresh water irrigation conditions. Collectively, it is assumed that biochar application to fertile soil in Nile Valley of Egypt could not alleviate tomato fruits yield reduction affected by applied saline irrigation regime.

Endogenous hormones improve the salt tolerance of maize (Zea mays L.) by inducing root architecture and ion balance optimizations

AbstractThe growth and development of maize is affected in a crucial way by the salinity of the soil it grows in. Therefore, if we want to improve the salt tolerance of maize, it is of paramount importance to understand how it responds to salt stress. To explore how maize adapts to a saline environment, we chose one salt‐tolerant maize variety, Jingnongyu 658 (JNY658), and one salt‐sensitive variety, Yunyu7 (YY7), and treated the seedlings of both varieties with a 100 mM NaCl solution. After harvesting them, we analysed the adaptive responses to salt stress with respect to various characteristics of the root architecture and water and nutrient acquisition. We found that when subjected to salt stress, both varieties exhibited a reduction in biomass, root activity, 15N and H218O uptake amount, lateral root branching density, lateral root length, total root length, root surface area and root volume, where the YY7 suffered a greater reduction than the JNY658. Salt stress also induced a decreased absorption of K+, passively promoted the absorption of Na+ and gave rise to an increased Na+/K+ ratio in the roots of both varieties. It should be noted that JNY658 exposed to salt stress developed a lower Na+/K+ ratio than YY7. Compared with the control group, the expression of ZmSOS1, ZmSOS2 and ZmNHX genes in the roots of JNY658 subjected to salt stress was significantly upregulated, which enabled them to maintain a lower Na+ content. In both varieties, the salicylic acid (SA) and gibberellin19 acid (GA19) content increased significantly, but the auxin (IAA), jasmonic acid (JA) and trans‐zeatin (TZ) content was reduced. In addition, JNY658 in salt stress significantly increased their abscisic acid (ABA) content, due to the increased expression of its key biosynthesis genes, NCED. Compared with JNY658, the reductions in IAA, JA and TZ content in YY7 were greater, while the increases in ABA and SA content were smaller. The varieties in the ABA, JA, SA and IAA of roots subjected to salt stress significantly or extremely significantly correlated with the lateral root branching density, lateral root length, root surface area, Na+ content, K+ content and Na+/K+ ratio. We conclude that the salt‐tolerant maize variety mitigated the toxic effect of salinity on maize root growth and development by regulating the hormone content and enhancing its expression of stress‐responsive genes while maintaining ion homeostasis and promoting water and nutrient acquisition, which ultimately resulted in a less pronounced decrease in plant biomass.

Lateral root elongation enhances nitrogen-use efficiency in maize genotypes at the seedling stage.

BACKGROUNDMaize plants show great variation in root morphological response to nitrogen (N) deficit, and such alterations often determine N‐use efficiency (NUE) plants. This study assessed genotypic variation in root morphology and NUE in selected 20 maize genotypes with contrasting root system size grown in a semi‐hydroponic phenotyping system for 38 days under control (4 mmol L−1 NO3 −) and low N (LN) (40 μmol L−1) for 38 days after transplanting.RESULTSMaize genotypes exhibited different responses to LN stress in each of the 28 measured shoot and root traits. The 20 genotypes were assigned into one of the three groups: N‐efficient (eight genotypes), medium (four genotypes), and N‐inefficient (eight genotypes), based on shoot dry weight ratio (the ratio of shoot dry weight at LN and control) ± one standard error. In response to LN stress, the N‐inefficient genotypes had significant reduction in biomass production by ~58% in shoots and ~64% in roots, while the N‐efficient genotypes maintained their biomass. Under LN supply N‐efficient genotypes showed a plasticity response that would result in both sparse lateral branching and increased root elongation as a whole or at each growth strata, and N efficiency positively correlated with lateral or axial root elongation and root elongation at different depths.CONCLUTSIONThe total lateral root length was the main contributor to the improved N foraging and utilization in maize under LN conditions, followed by axial root length. Total lateral root length can be considered in breeding programs for producing maize cultivars with high NUE at the early seedling stage. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

EFFECT OF DIETHYL SULPHATE ON M1 ATTRIBUTES AND SDS-PAGE ANALYSIS IN GROUNDNUT (Arachis hypogaea L.)

The present study was carried out to know the effect of diethyl sulphate on groundnut cultivar TMV-7 particularly in M1 generation. The healthy and viable seeds of groundnut cultivar TMV-7 were exposed to different concentrations of diethyl sulphate (5 to 25 mM) and sown in the field. The various growth and morphological parameters like percentage of seed germination, survival percentage plant height, days to flowering, total height at time of harvest, root length and number of lateral roots, number of pods per plant and pod weight were decreased with increasing concentrations of diethyl sulphate. All the characteristics studied were inhibited when compared to control. The lower concentrations such as 5, 10 and 15 mM concentrations enhanced all the parameters. But there was a sudden decrease in 20 and 25 mM. The various concentrations of DES played a different role in the field condition itself. The shoots developed from different concentrations of DES showed variation in their number and height. The protein content also showed decreasing trend with increasing concentrations of DES. There was a steady increase of protein content up to 15 mM DES. After that, there was a drastic reduction in the protein content in 20 and 25 mM. From the diethyl sulphate treated seeds, the embryo axes were collected and subjected to SDS-PAGE analysis. The protein banding pattern also differentiated among various concentrations of DES. The protein band with 77.5 kDa was observed in 5 and 10mM treatments. Like that the 13.5 kDa was present in 10 and 25mM treatments. The 48.25 kDa recorded in 15 and 20 mM treatments.

Effects on the root morphology and mircostructure of young pear (Pyrus pyrifolia) tree by split-root supply of bioorganic and chemical fertilizer

Bioorganic fertilizers are widely used in fruit orchards to improve soil properties and increase productivity. To investigate the effects of bioorganic fertilizer (BIO) and chemical fertilizer (CF) on the root system architecture and above-ground growth of pear trees, a split-root experiment was conducted. To this end, six soil amendment combinations were investigated: NF–NF (no fertilizer), NF-CF, NF-BIO, CF-CF, BIO-BIO, and BIO-CF. Roots of 1-year old ‘Cuiguan’ pear trees were distributed as evenly as possible into split-root chambers containing the aforementioned amendment combinations and maintained for 210 days after budding. Results showed that in boxes containing the same fertilizer in both chambers (NF–NF, CF-CF and BIO-BIO), the BIO chambers had an improved soil pH, by 0.6–0.8 units, and 23%–65.5% greater SOM than the soils in the NF and CF chambers. We also found that in these BIO chambers the lateral root number was 2.1–3.5 times greater than in NF and CF chambers and the maximum order of lateral roots was greater than 9. BIO application promoted lateral root growth in the paired NF and CF chambers, increasing specific root length and reducing root tissue density. In BIO-CF boxes, the 4th to 6th lateral root number and length accounted for the largest proportion of total lateral root number and length respectively. Moreover, compared with trees grown in CF-CF, those grown in BIO-BIO and BIO-CF had greater mean xylem, phloem, and cork layer thicknesses, as well as greater mean vessel density and number. BIO-CF treated soils had significantly reduced (50%) available phosphorus content compared to CF-CF treated soils, and consistently, BIO-CF resulted in the greatest growth of trunk girth (by 5–29%) among all the treatments. Soil organic matter and nitrate nitrogen concentration had significantly positive effects on root growth and activity, while branching intensity was significantly related to available phosphorus content and total nitrogen, followed by available potassium content and ammonia nitrogen content. In conclusion, local application of bioorganic fertilizer is a promising technique to sustainably maintain pear tree productivity because it accelerates the root proliferation and activity in either nutrient-deficient or -sufficient soil.

Using CRISPR-Kill for organ specific cell elimination by cleavage of tandem repeats

CRISPR/Cas has been mainly used for mutagenesis through the induction of double strand breaks (DSBs) within unique protein-coding genes. Using the SaCas9 nuclease to induce multiple DSBs in functional repetitive DNA of Arabidopsis thaliana, we can now show that cell death can be induced in a controlled way. This approach, named CRISPR-Kill, can be used as tool for tissue engineering. By simply exchanging the constitutive promoter of SaCas9 with cell type-specific promoters, it is possible to block organogenesis in Arabidopsis. By AP1-specific expression of CRISPR-Kill, we are able to restore the apetala1 phenotype and to specifically eliminate petals. In addition, by expressing CRISPR-Kill in root-specific pericycle cells, we are able to dramatically reduce the number and the length of lateral roots. In the future, the application of CRISPR-Kill may not only help to control development but could also be used to change the biochemical properties of plants.

Evaluation of 11 potential trap crops for root-knot nematode (RKN) control under glasshouse conditions

Abstract A preliminary study of the development and growth of lettuce crops trap cropped with 11 trap crops for root-knot nematode (RKN) control was studied under glasshouse conditions in Kadoorie Agriculture Research Centre in Palestine Technical University. Main crop growth parameters were evaluated by measuring the shoot height, lateral root length, wet and dry weight, ash percentage, and chlorophyll content. The total RKNs recovered from both main and trap crops from root systems were counted 6 weeks post RKN artificial inoculation. The first screening of the potential trap crops against RKNs showed a significant reduction in nematode numbers in lettuce and the average number of galls per gram fresh root when trap cropped with canola, B.G. pumpkin, mustard, and vetch cv. 976. No eggs were found by the end of the experiment. These trap crops attracted more nematodes and kept them from infecting the main crop. The effect of these trap crops on the growth and development of the main crop was variable. Trap cropping lettuce with canola, mustard, Armenian cucumber, and bottle gourd pumpkin caused a significant reduction of the total wet weight and dry weight compared with the control. Still, trap cropping did not significantly affect the lateral root length and wet weight. Removing the trap crops from the field after 6–8 weeks could be applied to reduce the competition between the main crop and the trap crops.

Trade-offs in Root and Shoot Growth in Forage Pea [Pisum sativum (L.) arvense] with Foliar Applications of Synthetic Elicitor DPMP (2,4-Dichloro-6-{(E)-[(3-Methoxyphenyl) Imino] Methyl} Phenol) and SA (Salicylic Acid)

Background: Climate change, abiotic and biotic stress pressure are forcing breeders and farmers to find alternative ways to improve and extend food production. Even though there are multiple ways to cope with stress conditions, alleviation of the stress by enhancing plant responses is one of the cheapest, environmentally safest and most direct ways. This study aimed to evaluate the effects of two common plant defense elicitors, 2,4-dichloro-6-{(E)-[(3-methoxyphenyl) imino] methyl} phenol (DPMP) and salicylic acid (SA) on plant growth and seedling vigor with forage pea [Pisum sativum (L.) arvense] as a model plant. Methods: Two different chemicals, 100 µM SA and 10 µM DPMP were evaluated in response to Polyethylene glycol 8000 (PEG) treatment in a semi-hydroponic growth system. Root architecture and shoot growth parameters were evaluated. The experiment was designed according to completely randomized design with three replications and ten plants per replication. Result: The effects of SA and DPMP foliar applications were significant on tap, lateral and total root lengths, number of lateral roots and root fresh weight. For most of the traits, SA and DPMP did not inhibit plant growth compared to control under treated and untreated conditions. Average lateral root length (aLatRL) was the noteworthy trait with significantly higher values in DPMP + unstressed conditions. Plants sprayed with DPMP had significantly higher (5.57 cm plant-1) aLatRL values compared to SA (4.53 cm plant-1) and control (3.01 cm plant-1). The results of the current study suggest that SA and DPMP foliar spraying can be beneficial to reduce the effects of abiotic stresses at optimal doses defined for each species. DPMP can be a candidate as a sustainable pesticide alternative and growth-enhancing agent, similar to SA.

Influence of Super Absorbent Polymer on Root Characteristics and Anchorage of Amorpha fruticosa on Rocky Slope

Super absorbent polymer (SAP), known as a water retention agent, has a high capacity for water absorption, which can help enhance the soil structure. This paper studied the effects of SAP dosages on the root characteristics and anchorage of Amorpha fruticosa on rock slopes. The internal relationship between root growth effect and soil was discussed, and a specific reference was provided for the rational application of SAP on slopes. Using the pull-out and tensile resistance tests, we systematically studied the changes of soil properties, root distribution, root tensile strength, and root anchorage under six different SAP dosages. The results indicated that: (1) With the increase in SAP dosage, the natural soil water content and water content after 24 h of watering increased significantly, whereas the contents of TN, TP, and TK decreased dramatically. (2) With the increase in SAP dosage, the amount and length of first-order and secondary lateral roots decreased significantly, and there was no significant difference in diameter. The amount of downslope first-order and unembedded secondary lateral roots is greater than upslope. The amount of upslope embedded secondary lateral roots is greater than in downslope. (3) Tensile strength: embedded secondary root > non-embedded secondary root > first-order lateral root; upslope root > downslope root. (4) With the increase in SAP dosage, the plant anchorage drops noticeably. This study concluded that the significant addition of SAP could enhance the tensile strength of upslope embedded secondary lateral roots but would adversely affect soil nutrients, root distribution, and root anchorage. The addition of SAP in this test had no significant effect on improving slope stability. From the perspective of reinforcement capacity, we cannot blindly pursue the survival rate and other high dosage use of water retention agents to increase the risk of slope destabilization.

Shaping the root system architecture in plants for adaptation to drought stress.

Root system architecture plays an important role in plant adaptation to drought stress. The root system architecture (RSA) consists of several structural features, which includes number and length of main and lateral roots along with the density and length of root hairs. These features exhibit plasticity under water-limited environments and could be critical to developing crops with efficient root systems for adaptation under drought. Recent advances in the omics approaches have significantly improved our understanding of the regulatory mechanisms of RSA remodeling under drought and the identification of genes and other regulatory elements. Plant response to drought stress at physiological, morphological, biochemical, and molecular levels in root cells is regulated by various phytohormones and their crosstalk. Stress-induced reactive oxygen species play a significant role in regulating root growth and development under drought stress. Several transcription factors responsible for the regulation of RSA under drought have proven to be beneficial for developing drought tolerant crops. Molecular breeding programs for developing drought-tolerant crops have been greatly benefitted by the availability of quantitative trait loci (QTLs) associated with the RSA regulation. In the present review, we have discussed the role of various QTLs, signaling components, transcription factors, microRNAs and crosstalk among various phytohormones in shaping RSA and present future research directions to better understand various factors involved in RSA remodeling for adaptation to drought stress. We believe that the information provided herein may be helpful in devising strategies to develop crops with better RSA for efficient uptake and utilization of water and nutrients under drought conditions.

Modification of plasma membrane H+-ATPase in Masson pine (Pinus massoniana Lamb.) seedling roots adapting to acid deposition.

To understand the regulation of roots plasma membrane H+-ATPase in Masson pine responding to acid deposition, the changes in biomass, plant morphology, intracellular H+, enzyme activity and H+-ATPase genes expression in Masson pine seedlings exposed to simulated acid rain (SAR, pH 5.6 and 4.6) with and without vanadate were studied. Simulated acid rain exposure for 60days increased the intracellular H+ in pine roots whether added with 0.1mM Na3VO4 or not. The growth of seedlings treated with SAR was maintained well, even the primary lateral root length, root dry weight and number of root tips in seedlings exposed to SAR at pH 4.6 were higher than that of the control (pH 6.6). However, the addition of vanadate resulted in severe growth inhibition and obvious decline in morphological parameters. Similarly, ATP hydrolytic activity and H+ transport activity of roots plasma membrane H+-ATPase, both were stimulated by SAR whereas they were inhibited by vanadate, and the highest activity stimulation was observed in pine roots subjected to SAR at pH4.6. In addition, SAR also induced the expression of the investigated H+-ATPase subunits (atpB, atpE, atpF, atpH and atpI). Therefore, the roots plasma membrane H+-ATPase is instrumental in the growth of Masson pine seedlings adapting to acid rain by a manner of pumping more protons across the membrane through enhancing its activity, and which involves the upregulated gene expression of roots H+-ATPase subunits at transcriptional level.

New insights into the role of chrysanthemum calcineurin B\u2013like interacting protein kinase CmCIPK23 in nitrate signaling in Arabidopsis roots

Nitrate is an important source of nitrogen and also acts as a signaling molecule to trigger numerous physiological, growth, and developmental processes throughout the life of the plant. Many nitrate transporters, transcription factors, and protein kinases participate in the regulation of nitrate signaling. Here, we identified a gene encoding the chrysanthemum calcineurin B-like interacting protein kinase CmCIPK23, which participates in nitrate signaling pathways. In Arabidopsis, overexpression of CmCIPK23 significantly decreased lateral root number and length and primary root length compared to the WT when grown on modified Murashige and Skoog medium with KNO3 as the sole nitrogen source (modified MS). The expression of nitrate-responsive genes differed significantly between CmCIPK23-overexpressing Arabidopsis (CmCIPK23-OE) and the WT after nitrate treatment. Nitrate content was significantly lower in CmCIPK23-OE roots, which may have resulted from reduced nitrate uptake at high external nitrate concentrations (≥ 1 mM). Nitrate reductase activity and the expression of nitrate reductase and glutamine synthase genes were lower in CmCIPK23-OE roots. We also found that CmCIPK23 interacted with the transcription factor CmTGA1, whose Arabidopsis homolog regulates the nitrate response. We inferred that CmCIPK23 overexpression influences root development on modified MS medium, as well as root nitrate uptake and assimilation at high external nitrate supply. These findings offer new perspectives on the mechanisms by which the chrysanthemum CBL interacting protein kinase CmCIPK23 influences nitrate signaling.

Effects of Phosphorus on Growth and Development of Soybean Seedlings

Soybean seedlings were treated with different phosphorus (P) concentrations for 20 days to investigate their growth and development. The root growth and development of soybean seedlings was the best when the concentration of phosphorus was 250 μmol/L. After 20 days of cultivation at this concentration, the roots of soybean seedlings were developed, indicating that the main root length, lateral root length, and the number of lateral root was the best among all treatments, and the number of lateral roots was quite a few. In addition, when the concentration of P was at 250 μmol/L, it had a better promotion effect on the plant height of soybean seedlings, and could significantly enhance the development of soybean seedlings. Moreover, the growth of soybean seedlings would be inhibited at the condition of phosphorus deficiency or excessive phosphorus. In this experiment, the growth indexes of soybean seedlings were compared between four treatments of phosphorus concentration, so as to make a basic study on the physiological effect of soybean on phosphorus in early stage.