Promoted Root Development Research Articles

Overexpression of SoCYP85A1, a Spinach Cytochrome p450 Gene in Transgenic Tobacco Enhances Root Development and Drought Stress Tolerance.

Brassinosteroids (BRs) play an essential role in plant growth, development, and responses to diverse abiotic stresses. However, previous studies mainly analyzed how exogenous BRs influenced plant physiological reactions to drought stress, therefore, genetic evidences for the endogenous BRs-mediated regulation of plant responses still remain elusive. In this study, a key BRs biosynthetic gene, SoCYP85A1 was cloned from Spinacia oleracea, which has a complete open reading frame of 1,392 bp encoding a 464 amino acid peptide and shares high sequence similarities with CYP85A1 from other plants. The expression of SoCYP85A1 which was higher in leaf compared with root and stem, was induced by treatments of PEG6000, abscisic acid (ABA), low temperature and high salt. Increases in both SoCYP85A1 transcripts and endogenous BRs in transgenic tobacco which resulted in longer primary root and more lateral roots enhanced drought tolerance compared with wild types. The transgenic tobacco accumulated much lower levels of reactive oxygen species and malondialdehyde (MDA) than wild types did, accompanied by significantly higher content of proline and notably enhanced activities of antioxidant enzymes. Besides, transcriptional expressions of six stress-responsive genes were regulated to higher levels in transgenic lines under drought stress. Taken together, our results demonstrated that SoCYP85A1 involves in response to drought stress by promoting root development, scavenging ROS, and regulating expressions of stress-responsive genes.

Enhanced root growth in phosphate-starved Arabidopsis by stimulating de novo phospholipid biosynthesis through the overexpression of LYSOPHOSPHATIDIC ACID ACYLTRANSFERASE 2 (LPAT2).

Upon phosphate starvation, plants retard shoot growth but promote root development presumably to enhance phosphate assimilation from the ground. Membrane lipid remodelling is a metabolic adaptation that replaces membrane phospholipids by non-phosphorous galactolipids, thereby allowing plants to obtain scarce phosphate yet maintain the membrane structure. However, stoichiometry of this phospholipid-to-galactolipid conversion may not account for the massive demand of membrane lipids that enables active growth of roots under phosphate starvation, thereby suggesting the involvement of de novo phospholipid biosynthesis, which is not represented in the current model. We overexpressed an endoplasmic reticulum-localized lysophosphatidic acid acyltransferase, LPAT2, a key enzyme that catalyses the last step of de novo phospholipid biosynthesis. Two independent LPAT2 overexpression lines showed no visible phenotype under normal conditions but showed increased root length under phosphate starvation, with no effect on phosphate starvation response including marker gene expression, root hair development and anthocyanin accumulation. Accompanying membrane glycerolipid profiling of LPAT2-overexpressing plants revealed an increased content of major phospholipid classes and distinct responses to phosphate starvation between shoot and root. The findings propose a revised model of membrane lipid remodelling, in which de novo phospholipid biosynthesis mediated by LPAT2 contributes significantly to root development under phosphate starvation.

Effect of soil condition on apple root development and plant resilience in intensive orchards

The sustainability of intensively managed orchards relies on the endogenous plant mechanisms of resilience. The plasticity of plants in their responses to external stimuli determines their tolerance to stress, and has to be promoted by growers. High-density orchard management has the advantage of the use of a root system that can promptly respond to changing conditions. Thus, it has become of pivotal importance to explore the soil–plant relationships and to highlight management practices that promote root development. This applies especially to the root fibrous fraction, which is mostly active in absorption, as well as the root activity and lifespan. Moreover, for intensive orchards that are highly exposed to replanting diseases, sustainable management should promote accumulation of homospecific residues, possibly by accelerating the cycles of degradation of allelopathic compounds. This report summarises a set of studies that were conducted to determine the effects of soil fertility and amendments on apple root morphology and physiology, and it highlights the relevance of soil management practices in promoting efficient root development.

Pulp and dentin modifications that occur after direct and indirect overlay with materials on the calcium hydroxide-base

When pulp tissue gets exposed, therapy procedures are supposed to promote healing and to ease forming of reparative dentin in order to preserve vitality and health of the pulp. Vital pulp therapy (VPT) procedure includes removal of the local irritants as well as application of protective materials directly or indirectly on tooth pulp. Vital pulp therapy may be used for the treatment of the reversible pulp diseases in order to promote root development and to form apical region which will ensure correct endodontic tooth treatment in later stages. There are numerous controversies concerning vital pulp therapy but mostly related to the choice of the materials, correct technique and evaluation of the final therapy results. The goal of the experimental research is to use scanning electron and polarized microscopy to analyze modifications on cellular and extracellular components of the tooth pulp after direct and indirect overlaying with materials on the calcium hydroxide basis (Calcimol VOCO USA). We will also determine the appearance of dental surface after direct and indirect overlaying and if Calcimol proves good and effective in dentinogenesis, we will propose it for clinical usage. Research has been conducted on experimental animals (pig). Materials used in this research were on calcium hydroxide - base, Calcimol. V class preparation has been applied on the teeth of the experimental group. Eleven teeth have been overlaids directly and the same number of teeth has been overlaid indirectly. After the preparation, materials based on calcium hydroxide have been applied and cavity has been closed with materials from the glass ionomer cement group (FUJI IX GC Japan). Teeth that were treated with pulp perforation had their chambers filled with materials on calcium hydroxide-base and their cavities were closed with glass ionomer cement (FUJI IX GC Japan). Correctly prepared teeth have been observed with SEM and polarization microscopes. Observing and analyzing of the results with polarization and scanning electron microscope in comparison with control group showed that gained results may have significant clinical implication in biological pulp treatment. Directly applied Calcimol observed through polarization microscope points to intensive changes in blood vessels and beginnings of erythrocyte disintegration, distinct extravasation, and appearance of the small necrotic spots. SEM analyzes shows contact of the amalgam-Calcimol without new amorphous dentinal structures. Indirectly applied Calcimol observed through polarization microscope points to newly formed dentinal structures, calcification cores surrounded by huge cells and blood vessels presence. SEM analyzes shows clear border between newly formed dentinal tubules and ordinary dentinal structure. Gained results suggest application of the Calcimol as a material for indirect pulp overlay while its application in indirect overlay isn't indicated.

Regulation of Plant Growth, Photosynthesis, Antioxidation and Osmosis by an Arbuscular Mycorrhizal Fungus in Watermelon Seedlings under Well-Watered and Drought Conditions.

Drought stress has become an increasingly serious environmental issue that influences the growth and production of watermelon. Previous studies found that arbuscular mycorrhizal (AM) colonization improved the fruit yield and water use efficiency (WUE) of watermelon grown under water stress; however, the exact mechanisms remain unknown. In this study, the effects of Glomus versiforme symbiosis on the growth, physio-biochemical attributes, and stress-responsive gene expressions of watermelon seedlings grown under well-watered and drought conditions were investigated. The results showed that AM colonization did not significantly influence the shoot growth of watermelon seedlings under well-watered conditions but did promote root development irrespective of water treatment. Drought stress decreased the leaf relative water content and chlorophyll concentration, but to a lesser extent in the AM plants. Compared with the non-mycorrhizal seedlings, mycorrhizal plants had higher non-photochemical quenching values, which reduced the chloroplast ultrastructural damage in the mesophyll cells and thus maintained higher photosynthetic efficiency. Moreover, AM inoculation led to significant enhancements in the enzyme activities and gene expressions of superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase, and monodehydroascorbate reductase in watermelon leaves upon drought imposition. Consequently, AM plants exhibited lower accumulation of MDA, H2O2 and compared with non-mycorrhizal plants. Under drought stress, the soluble sugar and proline contents were significantly increased, and further enhancements were observed by pre-treating the drought-stressed plants with AM. Taken together, our findings indicate that mycorrhizal colonization enhances watermelon drought tolerance through a stronger root system, greater protection of photosynthetic apparatus, a more efficient antioxidant system and improved osmoregulation. This study contributes to advances in the knowledge of AM-induced drought tolerance.

Evaluation of the orthodontic treatment outcome in patients with impacted maxillary central incisor in the mixed dentition

To evaluate the orthodontic treatment outcome in patients with impacted maxillary central incisor in the mixed dentition. Nine patients, aged 8 to 11 years, with impacted maxillary central incisor were treated orthodontically. The cone-beam CT(CBCT) was taken before treatment, after treatment and one year out of retention to evaluate the root length, root canal wall thickness, width of the apical foramen, and degree of root bending, alveolar bone height and thickness. The crown-to-root ratio was calculated. The periodontal and endodontic conditions were evaluated. The parameters of the treated incisors and contralateral ones served as controls were compared. Nine impacted teeth were treated successfully. Throughout the treatment, the root of impacted central incisor continued to develop and the alveolar bones also continued to develop and remodel. The condition of the alveolar bone of vertically impacted teeth was better than that of horizontally impacted ones. No periodontal pocket or pulp necrosis was found after treatment. Seven patients were examined one year after treatment. No significant difference was found in root length, palatal alveolar bone level and palatal alveolar bone thickness. The control group root length was (13.07±2.15) mm, the treatment group root length was (12.06±2.00) mm. No further alveolar bone loss, gingival recession and pulp necrosis were found. The control group labial and palatal alveolar bone levels were (0.90±0.62), (0.45±0.52) mm, labial and palatal alveolar bone thickness were (0.85±0.14), (1.21±0.41) mm. The treatment group labial and palatal alveolar bone levels were (2.18±1.59) mm, (0.57±0.71) mm, labial and palatal alveolar bone thickness were (0.48±0.29), (1.43±0.31) mm. Orthodontic therapy for impacted maxillary central incisor in the mixed dentition could promote root development and alveolar bone remodeling. Good periodontal and endodontic conditions were achieved.

Low Nitrogen Fertigation Promotes Root Development and Transplant Quality in Globe Artichoke

Effective nutrition and irrigation are important nursery strategies to produce high-quality seedlings able to withstand heat and drought stress in the field. The objectives of this study were 2-fold, first to identify the influence of two nitrogen (N) levels (75 and 150 mg·L−1) and two fertigation (FR) methods, overhead (OH) and flotation (FL) of artichoke (Cynara cardunculus cv. Green Globe Improved) transplants on root/shoot growth and leaf physiology during the nursery period. A repeated greenhouse experiment was conducted and morphophysiological measurements were determined at 4 and 7 weeks after seeding (WAS). The second objective was to determine the impact of the nursery treatments (FR method and N level) on the subsequent crop growth and yield under three field irrigation methods [surface drip, subsurface drip, and overhead-linear system (OH-L)]. Field measurements were conducted at 50 and 150 days after field transplanting (DAT) during Fall–Winter 2015. Transplants fertilized with 75 mg·L−1 N (low N) had improved root components as compared to those with 150 mg·L−1 N (high N), especially at 4 WAS. The low N transplants had higher root surface area, root length, root branching, thinner root diameter, and less shoot area than the high N transplants. Wilting for low N transplants was 13.5% less than that for high N at 5 DAT, with a total yield similar or slightly higher than those of high N. Although growth of OH and FL transplants was statistically similar at transplanting, those irrigated with OH (greenhouse) had a 10% higher yield than FL irrigated transplants, regardless of the field irrigation method evaluated. Overall, low N level (75 mg·L−1 N) applied with OH irrigation in the nursery positively improved the transplant root system and transplant quality of artichoke seedlings.

The treatment timing of labial inversely impacted maxillary central incisors: A prospective study.

To determine the timing of treatment for the labial inversely impacted maxillary central incisors. Twenty-eight patients (mean age, 8.2 years) with labial inversely impacted maxillary central incisors were divided into early-treated and later-treated groups according to their dental age. All of the patients were treated with a combination of surgery and orthodontic traction using the Guide rod appliance. Cone-beam computed tomography images were taken immediately after treatment for assessing the root morphology, root length, and alveolar bone loss. Sagittal slices were evaluated at the widest labial-lingual width of the tooth in the axial view. All variables were evaluated by Simplant 13.0 software (Materialise Dental NV, Leuven, Belgium). The rank sum test indicated that the root length of two groups showed a statistically significant difference between the impacted and homonym tooth, with a shorter length in the impacted tooth (P < .05). The D-value (difference of root length between the impacted and homonym tooth) and alveolar bone loss on the labial side of the impacted incisor are significantly less in the early-treated groups when compared with the later-treated groups (P < .05). Spearman rank correlation analysis showed a statistically positive association between the treatment timing and D-value (r = .623, P < .05). The chi-square test for morphology of root apex indicated that the incidence of the root-apex-directed labial side is significantly higher in the later-treated groups when compared with the early-treated groups. The labial inversely impacted maxillary central incisors should be treated early to promote root development by achieving a better morphology of root apex, thus reducing the risk of alveolar bone loss on the labial side.

H+-pyrophosphatase from Salicornia europaea enhances tolerance to low phosphate under salinity in Arabidopsis

ABSTRACTIncreasing soil salinity threatens crop productivity worldwide. High soil salinity is usually accompanied by the low availability of many mineral nutrients. Here, we investigated the potential role that the H+- PPase could play in optimizing P use efficiency under salinity in plants. Transgenic Arabidopsis plants overexpressing either SeVP1 or SeVP2 from Salicornia europaea outperformed the wild-types under low phosphate (Pi) as well as low Pi plus salt conditions. Our results suggested that H+-PPase could increase external Pi acquisition through promoting root development and upregulating phosphate transporters, thus to protect plants from Pi limiting stress. This study provides a potential strategy for improving crop yields challenged by the co-occurrence of abiotic stresses.

A Novel Sucrose-Regulatory MADS-Box Transcription Factor GmNMHC5 Promotes Root Development and Nodulation in Soybean (Glycine max [L.] Merr.).

The MADS-box protein family includes many transcription factors that have a conserved DNA-binding MADS-box domain. The proteins in this family were originally recognized to play prominent roles in floral development. Recent findings, especially with regard to the regulatory roles of the AGL17 subfamily in root development, have greatly broadened their known functions. In this study, a gene from soybean (Glycine max [L.] Merr.), GmNMHC5, was cloned from the Zigongdongdou cultivar and identified as a member of the AGL17 subfamily. Real-time fluorescence quantitative PCR analysis showed that GmNMHC5 was expressed at much higher levels in roots and nodules than in other organs. The activation of expression was first examined in leaves and roots, followed by shoot apexes. GmNMHC5 expression levels rose sharply when the plants were treated under short-day conditions (SD) and started to pod, whereas low levels were maintained in non-podding plants under long-day conditions (LD). Furthermore, overexpression of GmNMHC5 in transgenic soybean significantly promoted lateral root development and nodule building. Moreover, GmNMHC5 is upregulated by exogenous sucrose. These results indicate that GmNMHC5 can sense the sucrose signal and plays significant roles in lateral root development and nodule building.

A wheat salinity-induced WRKY transcription factor TaWRKY93 confers multiple abiotic stress tolerance in Arabidopsis thaliana

Wheat is an important crop in the world. But most of the cultivars are salt sensitive, and often adversely affected by salt stress. WRKY transcription factors play a major role in plant responses to salt stress, but the effective salinity regulatory WRKYs identified in bread wheat are limited and the mechanism of salt stress tolerance is also not well explored. Here, we identified a salt (NaCl) induced class II WRKY transcription factor TaWRKY93. Its transcript level was strongly induced by salt (NaCl) and exogenous abscisic acid (ABA). Over-expression of TaWRKY93 in Arabidopsis thaliana enhanced salt (NaCl), drought, low temperature and osmotic (mannitol) stress tolerance, mainly demonstrated by transgenic plants forming longer primary roots or more lateral roots on MS plates supplemented with NaCl and mannitol individually, higher survival rate under drought and low temperature stress. Further, transgenic plants maintained a more proline content, higher relative water content and less electrolyte leakage than the wild type plants. The transcript abundance of a series of abiotic stress-related genes was up-regulated in the TaWRKY93 transgenic plants. In summary, TaWRKY93 is a new positive regulator of abiotic stress, it may increase salinity, drought and low temperature stress tolerance through enhancing osmotic adjustment, maintaining membrane stability and increasing transcription of stress related genes, and contribute to the superior agricultural traits of SR3 through promoting root development. It can be used as a candidate gene for wheat transgenic engineering breeding against abiotic stress.

The inter-kingdom volatile signal indole promotes root development by interfering with auxin signalling.

Recently, emission of volatile organic compounds (VOCs) has emerged as a mode of communication between bacteria and plants. Although some bacterial VOCs that promote plant growth have been identified, their underlying mechanism of action is unknown. Here we demonstrate that indole, which was identified using a screen for Arabidopsis growth promotion by VOCs from soil-borne bacteria, is a potent plant-growth modulator. Its prominent role in increasing the plant secondary root network is mediated by interfering with the auxin-signalling machinery. Using auxin reporter lines and classic auxin physiological and transport assays we show that the indole signal invades the plant body, reaches zones of auxin activity and acts in a polar auxin transport-dependent bimodal mechanism to trigger differential cellular auxin responses. Our results suggest that indole, beyond its importance as a bacterial signal molecule, can serve as a remote messenger to manipulate plant growth and development.

Induction and proliferation of axillary shoots from in vitro culture of Paeonia lactiflora Pall. mature zygotic embryos

Zygotic embryos of three herbaceous peony (Paeonia lactiflora Pall.) cultivars (‘Fen Yu Nu’, ‘Zhong Sheng Fen’ and ‘Zhu Sha Pan’) were used to study embryo germination and optimum plant growth regulator (PGR) combinations for in vitro propagation and root initiation. Mature zygotic embryos (>90 days after flowering [DAF]) gave better germination and survival than immature zygotic embryos (50–70 DAF). A protocol for initiating shoot growth and axillary shoot proliferation was established using mature embryos. The best results were obtained when using excised zygotic embryos (EZEs) obtained by removing the testa and endosperm from the seed. The best medium for EZE germination (an embryo with cotyledons) was half-strength Murashige and Skoog (MS) medium (with double-strength CaCl2) supplemented with 0.5 mg L−1 6-benzyladenine (BA) and 0.5 mg L−1 gibberellic acid (GA3). The best medium for axillary shoot proliferation was half-strength MS medium (including double-strength CaCl2) supplemented with 1 mg L−1 BA and 1 mg L−1 GA3. PGR-free half-strength MS was the best medium for promoting root development on seedlings (a germinated EZE with tender leaves) and for robust in vitro seedling establishment. The acclimatization of herbaceous peony remains the most challenging step of the in vitro protocol.

Evaluation of pinewood biochar as a carrier of bacterial strain Enterobacter cloacae UW5 for soil inoculation

The large-scale production of biochar for carbon sequestration provides an opportunity for using these materials as inoculum carriers to deliver plant growth-promoting rhizobacteria (PGPR) into agricultural soils. Here, we evaluated the suitability of a biochar produced from pinewood pyrolyzed at 300°C as a carrier for a well-studied PGPR strain, Enterobacter cloacae UW5. This strain was genetically modified to produce a green fluorescent protein marker that enabled tracking of the inoculum. Results from selective plate count assays and quantitative PCR (qPCR) confirmed that cell survival was slightly improved by addition of bacteria to soil using biochar as a carrier for the inoculant, as compared to soil directly inoculated. Total 16S rRNA genes were quantified using qPCR and DNA templates from the same soil treatments to distinguish the impact of biochar on total bacterial abundance from its influence on inoculum survival. Here total bacterial abundance was not influenced by biochar. All treatments resulted in bacterial colonization of roots at population densities of approximately 105CFUg−1 root mass. Cucumber plants grown in the biochar amended soils had significantly greater biomass and root development than those planted in un-amended soil, regardless of the presence of inoculum. The ability of bacteria to colonize the plant roots and produce a plant growth hormone was not affected by biochar. However, UW5 inoculum did not promote root development in cucumber in any of the soils tested here. Overall, these experiments suggest that the 300°C pine biochar is effective for evenly distributing inoculum into soil and promotes cucumber development in sandy loams.

Effect of subsoil tillage depth on nutrient accumulation, root distribution, and grain yield in spring maize

A four-year field experiment was conducted to investigate the effect of subsoiling depth on root morphology, nitrogen (N), phosphorus (P), and potassium (K) uptake, and grain yield of spring maize. The results indicated that subsoil tillage promoted root development, increased nutrient accumulation, and increased yield. Compared with conventional soil management (CK), root length, root surface area, and root dry weight at 0–80cm soil depth under subsoil tillage to 30cm (T1) and subsoil tillage to 50cm (T2) were significantly increased, especially the proportions of roots in deeper soil. Root length, surface area, and dry weight differed significantly among three treatments in the order of T2>T1>CK at the 12-leaf and early filling stages. The range of variation of root diameter in different soil layers in T2 treatment was the smallest, suggesting that roots were more likely to grow downwards with deeper subsoil tillage in soil. The accumulation of N, P, and K in subsoil tillage treatment was significantly increased, but the proportions of kernel and straw were different. In a comparison of T1 with T2, the grain accumulated more N and P, while K accumulation in kernel and straw varied in different years. Grain yield and biomass were increased by 12.8% and 14.6% on average in subsoil tillage treatments compared to conventional soil treatment. Although no significant differences between different subsoil tillage depths were observed for nutrient accumulation and grain yield, lodging resistance of plants was significantly improved in subsoil tillage to 50cm, a characteristic that favors a high and stable yield under extreme environments.

Influence of straw mulching on soil water/salt movement and cotton root distribution under drip irrigation

干旱区棉田残膜污染日益严重, 秸秆覆盖能从根本上杜绝农田残膜增量。为探索秸秆覆盖代替塑料薄膜与滴灌结合的可行性, 需了解秸秆覆盖对滴灌棉田土壤水盐分布及棉花根系的影响特点, 同时探索耕作层以下30 cm处埋设一层秸秆进行深层秸秆覆盖与滴灌结合的效果。本文采用测坑试验研究了3种秸秆覆盖方式(表层覆盖、30 cm深层覆盖和无覆盖)与滴灌结合在2种土壤条件下(非盐碱土和盐碱土), 棉花根系分布稳定后的絮期土壤水盐运移及棉花根系分布特征。结果表明: 表层覆盖对于土壤整体保水性较好, 能有效抑制耕层水分散失和盐分聚集; 30 cm深层覆盖整体保水性优于无覆盖, 相对表层覆盖仅在秸秆层以下靠近滴灌带的有限范围内具有优势, 并显著提高耕层以下土壤水分含量, 但在棉花絮期对于盐分抑制作用不明显。秸秆覆盖通过对水盐运动的影响而显著影响棉花根系分布, 尤其对深层根系分布影响更大。非盐碱土条件下, 0~28 cm土层, 无覆盖处理根长密度、根重密度、根长密度比重均最大, 表层覆盖根长密度最小, 但根重比重最大, 30 cm深层覆盖根重密度最小; 在28~70 cm土层, 30 cm深层覆盖根长密度最大, 表层覆盖根长密度最小, 但根长密度比重最大, 无覆盖根长密度比重最小, 其中在28~56 cm土层30 cm深层覆盖根重密度和根重比重均最大。盐碱土条件下, 0~28 cm土层, 表层覆盖与30 cm深层覆盖根长密度和根长比重均高于无覆盖处理, 同时表层覆盖根重密度最高, 30 cm深层覆盖根重密度和根重比重均最低; 在28~70 cm土层情况相反, 30 cm深层覆盖处理根重比重最大, 但根重密度最小。说明表层覆盖可促进非盐碱土及盐碱土耕作层根系发育, 30 cm深层覆盖限制上层根系发育, 但促进30 cm以下土层根系发育, 在盐碱逆境下秸秆覆盖可促进根系向更细更长方面发育。秸秆覆盖与滴灌结合在干旱区具有良好应用前景。

A Conifer ABI3-Interacting Protein Plays Important Roles during Key Transitions of the Plant Life Cycle

ABI3 (for ABSCISIC ACID INSENSITIVE3), a transcription factor of the abscisic acid signal transduction pathway, plays a major role during seed development, dormancy inception, and dormancy maintenance. This protein appears to also function in meristematic and vegetative plant tissues and under certain stress conditions. We have isolated the ABI3 gene ortholog (CnABI3) from yellow cedar (Callitropsis nootkatensis) and found that it was functionally similar to other ABI3 genes of angiosperms. Here, we report that using a yeast (Saccharomyces cerevisiae) two-hybrid approach, we have identified another protein of yellow cedar (CnAIP2; for CnABI3 INTERACTING PROTEIN2) that physically interacts with CnABI3. Functional analyses revealed that CnAIP2 plays important roles during key transitions in the plant life cycle: (1) CnAIP2 impaired seed development and reduced seed dormancy; (2) CnAIP2 promoted root development, particularly the initiation of lateral roots, and the CnAIP2 gene promoter was exquisitely auxin sensitive; and (3) CnAIP2 promoted the transition from vegetative growth to reproductive initiation (i.e. flowering). The nature of the effects of CnAIP2 on these processes and other evidence place CnAIP2 in the category of a "global" regulator, whose actions are antagonistic to those of ABI3.

Growth and Leaf Gas Exchange in Three Birch Species Exposed to Elevated Ozone and CO2 in Summer

We examined the effects of ozone and elevated CO2 concentration in summer on the growth and photosynthetic traits of three representative birch species in Japan (mountain birch, Monarch birch, and white birch). Seedlings of the three birch species were grown in 16 open-top chambers and were exposed to two levels of ozone (6 and 60 nmol mol−1 for 7 h per day) in combination with two levels of CO2 (370–380 and 600 μmol mol−1 for daytime) from July to October. No adverse effects of ozone were found in the Monarch birch or the white birch, but elevated ozone in summer reduced branch biomass and net photosynthesis, and accelerated leaf abscission, in the mountain birch. Elevated CO2 promoted root development and thereby reduced the ratio of shoot dry mass (stem + branch) to root dry mass (S/R ratio) in the mountain birch and white birch. In contrast, there was no difference in dry mass between ambient and elevated CO2 for the Monarch birch, due to downregulation of photosynthesis. Studies of the combined effect of CO2 and ozone revealed that elevated CO2 did not ameliorate the effect of ozone on mountain birch in late summer. In considering the ameliorating effect of CO2 on ozone damage, it is necessary to take account of the species and the season.

Photosynthetic sucrose acts as cotyledon-derived long-distance signal to control root growth during early seedling development in Arabidopsis

The most hazardous span in the life of green plants is the period after germination when the developing seedling must reach the state of autotrophy before the nutrients stored in the seed are exhausted. The need for an economically optimized utilization of limited resources in this critical period is particularly obvious in species adopting the dispersal strategy of producing a large amount of tiny seeds. The model plant Arabidopsis thaliana belongs to this category. Arabidopsis seedlings promote root development only in the light. This response to light has long been recognized and recently discussed in terms of an organ-autonomous feature of photomorphogenesis directed by the red/blue light absorbing photoreceptors phytochrome and cryptochrome and mediated by hormones such as auxin and/or gibberellin. Here we show that the primary root of young Arabidopsis seedlings responds to an interorgan signal from the cotyledons and that phloem transport of photosynthesis-derived sugar into the root tip is necessary and sufficient for the regulation of root elongation growth by light.

DREB1A promotes root development in deep soil layers and increases water extraction under water stress in groundnut

Water deficit is a major yield-limiting factor for many crops, and improving the root system has been proposed as a promising breeding strategy, although not in groundnut (Arachis hypogaea L.). The present work was carried out mainly to assess how root traits are influenced under water stress in groundnut, whether transgenics can alter root traits, and whether putative changes lead to water extraction differences. Several transgenic events, transformed with DREB1A driven by the rd29 promoter, along with wild-type JL24, were tested in a lysimeter system that mimics field conditions under both water stress (WS) and well-watered (WW) conditions. The WS treatment increased the maximum rooting depth, although the increase was limited to about 20% in JL24, compared to 50% in RD11. The root dry weight followed a similar trend. Consequently, the root dry weight and length density of transgenics was higher in layers below 100-cm depth (Exp. 1) and below 30 cm (Exp. 2). The root diameter was unchanged under WS treatment, except a slight increase in the 60-90-cm layer. The root diameter increased below 60 cm in both treatments. In the WW treatment, total water extraction of RD33 was higher than in JL24 and other transgenic events, and somewhat lower in RD11 than in JL24. In the WS treatment, water extraction of RD2, RD11 and RD33 was higher than in JL24. These water extraction differences were mostly apparent in the initial 21 days after treatment imposition and were well related to root length density in the 30-60-cm layer (R(2) = 0.68), but not to average root length density. In conclusion, water stress promotes rooting growth more strongly in transgenic events than in the wild type, especially in deep soil layers, and this leads to increased water extraction. This opens an avenue for tapping these characteristics toward the improvement of drought adaptation in deep soil conditions, and toward a better understanding of genes involved in rooting in groundnut.