Retarded Shoot Growth Research Articles

Evaluation of shoot-growth variation in diverse carrot (Daucus carota L.) germplasm for genetic improvement of stand establishment.

Carrot (Daucus carota L.) is a high value, nutritious, and colorful crop, but delivering carrots from seed to table can be a struggle for carrot growers. Weed competitive ability is a critical trait for crop success that carrot and its apiaceous relatives often lack owing to their characteristic slow shoot growth and erratic seedling emergence, even among genetically uniform lines. This study is the first field-based, multi-year experiment to evaluate shoot-growth trait variation over a 100-day growing season in a carrot diversity panel (N=695) that includes genetically diverse carrot accessions from the United States Department of Agriculture National Plant Germplasm System. We report phenotypic variability for shoot-growth characteristics, the first broad-sense heritability estimates for seedling emergence (0.68 < H2 < 0.80) and early-season canopy coverage ( 0.61 < H2 < 0.65), and consistent broad-sense heritability for late-season canopy height (0.76 < H2 < 0.82), indicating quantitative inheritance and potential for improvement through plant breeding. Strong correlation between emergence and canopy coverage (0.62 < r < 0.72) suggests that improvement of seedling emergence has great potential to increase yield and weed competitive ability. Accessions with high emergence and vigorous canopy growth are of immediate use to breeders targeting stand establishment, weed-tolerance, or weed-suppressant carrots, which is of particular advantage to the organic carrot production sector, reducing the costs and labor associated with herbicide application and weeding. We developed a standardized vocabulary and protocol to describe shoot-growth and facilitate collaboration and communication across carrot research groups. Our study facilitates identification and utilization of carrot genetic resources, conservation of agrobiodiversity, and development of breeding stocks for weed-competitive ability, with the long-term goal of delivering improved carrot cultivars to breeders, growers, and consumers. Accession selection can be further optimized for efficient breeding by combining shoot growth data with phenological data in this study's companion paper to identify ideotypes based on global market needs.

Far-red light-enhanced apical dominance stimulates flower and fruit abortion in sweet pepper.

Far-red radiation affects many plant processes, including reproductive organ abortion. Our research aimed to determine the role of apical dominance in far-red light-induced flower and fruit abortion in sweet pepper (Capsicum annuum L.). We conducted several climate room experiments where plants were grown under white- or red-rich LED light, with or without additional far-red light. Additional far-red light enhanced apical dominance: it increased auxin levels in the apices of dominant shoots, and caused a greater difference in internode length and apical auxin levels between dominant and subordinate shoots. Additional far-red light stimulated fruit abortion in intact plants but not in decapitated plants, suggesting a crucial role of shoot apices in this effect. However, reducing basipetal auxin transport in the stems with N-1-naphthylphthalamic acid did not influence far-red light-stimulated fruit abortion, although auxin levels in the stem were largely reduced. Applying the synthetic auxin 1-naphthaleneacetic acid on decapitated apices did not influence fruit abortion. However, applying the auxin biosynthesis inhibitor yucasin to shoot apices reduced fruit abortion regardless of the light conditions, accompanied by slight shoot growth retardation. These findings suggest that the basipetal auxin stream does not mediate far-red light-stimulated fruit abortion. Far-red light-stimulated fruit abortion was associated with reduced sucrose accumulation and lower invertase activities in flowers. We suggest that under additional far-red light conditions, increased auxin levels in shoot apices promote fruit abortion probably through enhanced competition for assimilates between apices and flowers, which limits assimilate import into flowers.

Impact of the leaf‐mining jewel beetle Hedwigiella jureceki on two forms of cat's claw creeper, Dolichandra unguis‐cati

AbstractThe impact assessment of a weed biocontrol agent offers insight into the potential of the agent and weed responses in long‐term weed management. The impact of the jewel beetle Hedwigiella jureceki Obenberger (Coleoptera: Buprestidae) and its first‐generation larvae on the long‐pod (LP) and short‐pod (SP) forms of cat's claw creeper, Dolichandra unguis‐cati (L.) L.G. Lohmann (Bignoniaceae) was studied by initiating one, two, or five pairs (male and female) of adults in a glasshouse experiment. With the higher density of adults, the number of leaves increased significantly, as did the numbers of dead leaves and larval mines, and the percentages of affected leaves (up to 40%), and damaged leaf areas (up to 60%). Plants with the five pairs of adults had fewer leaves and reduced dry weights (e.g., tuber biomass was reduced by 50.4–62.5%). Regardless of adult density, the dry weights of the leaves and tubers were lower in the SP form. Conversely, the LP form had fewer leaves (ca. 17% fewer) and slower shoot growth (mean ± SE = 46.3 ± 2.6 cm per week) than the SP form (66.5 ± 3.8 cm per week). However, the number of tubers was not affected by the plant form and adult density. Larval mines (262 ± 30), pupae (186 ± 17), and adults (144 ± 14) in LP form were higher than in SP form (243 ± 20, 167 ± 14, and 115 ± 11, respectively). Likewise, the average weight of adults that emerged on the LP form was higher. Therefore, H. jureceki impacted both LP and SP forms. The SP form showed a higher impact in terms of reduced tuber growth, and the LP form is anticipated to be harmed more in the long term as a higher number of H. jureceki offspring developed on it when competition for food was increased.

Diversity in the morphology of clones of witches’ broom in Siberian stone pine

Mutational witches’ broom (WB) is a fragment of a tree crown with abnormally dense branching and slow shoot growth compared with those of a normal crown. All WBs have thicker and denser crown compared to the normal crown part of their parental tree, but the crown density differs significantly among WBs. There are both relatively loose WBs, whose crown density differ from normal crown part not very strong, and WBs with a very dense crown. The aim of this study was to conduct a comparative analysis of morphological traits in Pinus sibirica WB clones with different crown densities and to determine which traits contribute most to their differences. The object of the study was clones from 11 mutational WB with different crown density. The density of WB was considered low if it exceeded the density of a normal crown by less than 2 times, medium - by 2-3 times, high - by more than 3 times. Morphological characteristics of crown and shoots were measured in 12-year-old clones. It was found that the higher the WB clone crown density the smaller and less elongated its crown shape, as well as less crown continuity. The basis of this phenotype formation was primarily the shorter length of annual shoots, the reduced level of apical dominance compared to other clone groups, and advanced branching. An additional factor that increased crown density was the significantly shorter internodes compared to the other clone groups. The needle length did not contribute to the differences in crown density of the clones.

Cytokinin localization and dynamics in rye plants under chilling and kernel priming with zeatin

In the early stages of plant development, a sharp chilling can pose a significant threat to cold-resistant crops, such as winter cereals, in particular, rye. Phytohormones from the cytokinin family play a crucial role in regulating plant response to low-temperature stress. Pre-sowing seed priming with cytokinin solutions is a promising approach to improving the stress tolerance of cereals. The aim of this study was to investigate the impact of chilling on the dynamics and localization of cytokinins in plants of rye cv. Boguslavka in the early stages of development, to determine the possibility of mitigating the adverse effects of cold stress through kernel priming with a zeatin solution, and to assess the effect of this substance on the balance of endogenous cytokinins. Kernels were soaked in either water or a zeatin solution (10—6 М), and plants were grown under controlled conditions of the vegetation chamber. Chilling was induced by exposing 7-day-old plants to the refrigerator for 2 h or twice for 6 h over two days. Endogenous cytokinins were analyzed using the HPLC-MS method. We found significant changes in the cytokinin pool in plants exposed to 2 °C for 2 h while no morphological alterations were observed. The content of trans-zeatin and trans-zeatin riboside increased considerable in the shoots of the plants grown from the kernels soaked in water, whereas in the roots, the level of these cytokinins dropped sharply. Prolonged chilling led to retarded shoot growth and elongated roots. Simultaneously, the level of trans-zeatin, isopentenyladenosine and isopentenyladenine in the shoots decreased to minimum values, while the amount of trans-zeatin riboside increased almost twofold. Transformations of the cytokinin pool in the roots followed a similar pattern. Overall, under the cold stress at the alarm stage, cytokinin balance changes were aimed at maintaining growth processes, while during the acclimation stage, they contributed to growth inhibition. Pre-sowing priming of rye kernels with a zeatin solution allowed plants to maintain normal growth and morphology under of prolonged chilling. This treatment significantly affected the homeostasis of endogenous cytokinins, resulting in a more moderate rearrangement of the cytokinin pool in stressed plants than in the control. We assume that changes in the balance of cytokinins due to seed priming allow plants to improve cold tolerance. Seed treatment with cytokinins could be a promising approach to increasing the adaptive properties of plants.

Response of Pear Trees’ (Pyrus bretschneideri ‘Sinkiangensis’) Fine Roots to a Soil Water Regime of Regulated Deficit Irrigation

A field experiment was conducted to evaluate the effects of regulated deficit irrigation (RDI) on the fine root redistribution of mature pear trees in 2009 and 2010. The experiment consisted of four RDI treatments: MRDI-1 and SRDI-1, in which the trees received irrigation replacing 60% and 40% of pan evaporation (Ep) during Stage 1 (cell division stage), and MRDI-1+2 and SRDI-1+2, in which the trees received irrigation replacing 60% and 40% of Ep during Stage 1+2 (cell division and slow shoot growth stage). All the RDI-treated trees received irrigation replacing 80% of Ep (full irrigation) in other stages, and the control trees were fully irrigated during the whole growth season. The results showed that the fine root length density (RLD) of mature pear trees was reduced by water stress. The resumption of full irrigation boosted fine root growth. The RLD of the SRDI-1-treated trees in the irrigated zones recovered in early July, they maintained water and nutrient absorption during the fruit enlargement stage, and the final fruit yield was significantly improved. The RLD of trees in the irrigated zones with MRDI-1 and MRDI-1+2 recovered in July and September, respectively, but there were no significant differences in fruit yield between the MRDI-1, MRDI-1+2, and the control. This indicates that the fruit yield was not negatively or positively impacted by the redistribution of moderate water stress applied during either Stage 1 or Stage 1+2.

Aspects of cultivar variation in physiological traits related to Cd distribution in rice plants with a short-term stress

BackgroundGenotypic variations are seen in cadmium (Cd) tolerance and accumulation in rice plants. Cultivars that show low Cd translocation from the root into shoot can be selected to reduce Cd contamination in rice grains. This study aims to clarify the physiological regulation related to Cd absorption by rice plants for screening out the cultivars, which have relatively low Cd accumulation in grains. Eight Taiwan mega cultivars of paddy rice: japonica (TY3, TK9, TNG71, and KH145 cultivars), indica (TCS10 and TCS17 cultivars), and glutinous (TKW1 and TKW3 cultivars), which are qualified with the criteria for rice grain quality by the Council of Agriculture, Taiwan, were used for illustration. An experiment in hydroponics was conducted for the rice seedlings with a treatment of 50 μM CdCl2 for 7 days.Results and discussionAfter the Cd treatment, the reductions in shoot growth were more significant than those in root growth; however, Cd absorbed in the rice plant was sequestered much more in the root. The malondialdehyde (MDA) was preferentially accumulated in rice root but the hydrogen peroxide (H2O2) was increased more significantly in the shoot; the antioxidative enzymes, superoxide dismutase (SOD) and ascorbate peroxidase (APX), were pronounced more in rice shoot.ConclusionsThe rice cultivars preferentially accumulated Cd in the root rather than the shoot with the Cd treatment, which resulted in significant enhancements of MDA and growth reductions in the root. However, H2O2 accumulation was toward the shoot to retard shoot growth suddenly and then the root could keep a gradual growth. Also, the rice cultivars, which preferentially accumulate Cd in the root, would have the regulation tendency of SOD toward the shoot. Due to that SOD is responsible for H2O2 production, H2O2 accumulation would be thus toward the shoot. Moreover, the cultivars, which have a less regulation tendency of APX toward the shoot, would present higher translocation of Cd into the shoot.

Mathematical modeling of diurnal patterns of carbon allocation to shoot and root in Arabidopsis thaliana

We developed a mathematical model to simulate dynamics of central carbon metabolism over complete diurnal cycles for leaves of Arabidopsis thaliana exposed to either normal (120 µmol m−2 s−1) or high light intensities (1200 µmol m−2 s−1). The main objective was to obtain a high-resolution time series for metabolite dynamics as well as for shoot structural carbon formation (compounds with long residence time) and assimilate export of aerial organs to the sink tissue. Model development comprised a stepwise increment of complexity to finally approach the in vivo situation. The correct allocation of assimilates to either sink export or shoot structural carbon formation was a central goal of model development. Diurnal gain of structural carbon was calculated based on the daily increment in total photosynthetic carbon fixation, and this was the only parameter for structural carbon formation implemented in the model. Simulations of the dynamics of central metabolite pools revealed that shoot structural carbon formation occurred solely during the light phase but not during the night. The model allowed simulation of shoot structural carbon formation as a function of central leaf carbon metabolism under different environmental conditions without structural modifications. Model simulations were performed for the accession Landsberg erecta (Ler) and its hexokinase null-mutant gin2-1. This mutant displays a slow growth phenotype especially at increasing light intensities. Comparison of simulations revealed that the retarded shoot growth in the mutant resulted from an increased assimilate transport to sink organs. Due to its central function in sucrose cycling and sugar signaling, our findings suggest an important role of hexokinase-1 for carbon allocation to either shoot growth or assimilate export.

Cone structure and seed development in grafted witches’ broom and normal crown clones from the same trees of Pinus sibirica

Mutational witches’ broom represents a fragment of the tree crown with slower shoot growth, abnormally dense branching, decreased apical dominance and often with abundant cone-bearing compared with a normal crown. Mutational witches’ broom is a major source for the majority of ornamental dwarf conifer cultivars with abundant branching. Pinus sibirica is also capable of forming mutational witches’ brooms. The species has valuable edible seeds, and therefore, dwarf cultivars with abundant cone-bearing could be used to establish cone crop plantations. To reveal how the mutation causing witches’ broom affects the quality of cones and seeds, we carried out a comparative analysis of cone size, cone structure and seed quality in six grafted clones with witches’ broom and normal clones from the same trees, determining seed losses at the different developmental stages. Cones from mutant clones had 1.5–2.9 times smaller size than normal clones. Cones from 50% of the normal clones were more elongated in shape. In mutant clones, the numbers of fertile scales and ovules were 1.4 times lower than in normal clones. Seeds had a smaller size in all mutant clones, and seed quality and seed efficiency were lower in two-thirds of the clones compared with normal clones. Seed losses were observed at different developmental stages, but there were significantly more losses before pollination and during embryo development in mutants. Therefore, the majority of mutants had small cones and therefore a rather ornamental value because of reduced seed efficiency and small seeds. At the same time, individual mutant clones had a seed efficiency and the number of filled seeds close to those of normal clones. They could therefore be promising as cone-bearing cultivars for the commercial production of pine kernel.

Heavy metals and metalloids: Sources, risks and strategies to reduce their accumulation in horticultural crops

Abstract Food production in areas contaminated with heavy metals is associated with health risks because of their adverse effects on food safety and marketability, and on crop growth and yield quality. The present review focuses on sources and risks of heavy metals, mainly in cultivated fields in various regions, and strategies to reduce their accumulation in horticultural crops. The following heavy metals are discussed: arsenic (As), boron (B), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), lead (Pb), mercury (Hg), molybdenum (Mo), nickel (Ni), strontium (Sr), tin (Sn), titanium (Ti), vanadium (V) and zinc (Zn). Heavy metal sources in the environment can originate from natural and anthropogenic activities. Their main natural enrichment in soils stems from parent-material weathering. However, in coastal areas, precipitation of sea spray may enrich soil with B. In contrast, the main anthropogenic sources of heavy metals in cultivated areas are irrigation with treated sewage water, application of residual biosolids, and atmospheric pollution. Plants absorb heavy metals predominantly through roots and, to a lesser extent, through leaves. Leaf uptake can occur through the stomata, cuticular cracks, ectodesmata, and aqueous pores. Heavy metal uptake may lead to their accumulation in vegetables and fruit trees, and their consequent introduction into the food chain, which is recognized as one of the major pathways for human exposure to them. This exposure can result in retardation, several types of cancer, kidney damage, endocrine disruption, and immunological and neurological effects. High concentrations of heavy metals can also affect the growth and yield of many crops: Zn and Cd decrease plant metabolic activity and induce oxidative damage; Cu generates oxidative stress and reactive oxygen species; Hg can induce visible injury and physiological disorders; Cr affects photosynthesis in terms of CO2 fixation, electron transport, photophosphorylation and enzyme activities; Pb induces plant abnormal morphology; Ni spoils the nutrient balance, resulting in disorders of cell membrane functions; Fe causes free radical production that irreversibly impairs cell structure and damages membranes, DNA and proteins; As causes leaf necrosis and wilting, followed by root discoloration and retardation of shoot growth. Therefore, international organizations, such as the US EPA and EU bodies, are working on regulating the maximum allowable levels of food pollutants. A number of direct (mycorrhiza, transgenic plants and grafting) approaches can be deployed to overcome problems of heavy metal contamination in horticulture.

Cone quality and seed efficiency in the clones from mutational witches brooms ofPinus sibirica

Mutational witches' broom is a fragment of the tree crown with abnormal morphogenesis including slow shoot growth, abundant branching and decreased apical dominance which caused by somatic mutation that presumably originates in the apical meristem bud. To study the variability in the cone quality and seed efficiency in witches' broom clones ofPinus sibirica, the cone size and structure were assessed in 21 mutant clones. The mutant clones were significantly differentiated both by the cone traits and seed quality. Their cone size varied from less than 3 to 4 cm. The clones had large number of sterile scales in proximal and distal cone parts, and from 16 to 39 fertile scales per cone. Cones from all mutant clones were inferior to average normal cones of the species. Six clones had large portion of filled seeds, more than 70%, and the other clones had less than 50% of filled seeds. The clones had 10-33% of empty seeds and 1-73% of seeds with collapsed megagametophyte per cone. In general, the seed quality in mutants was quite low, but individual clones had almost normal seed quality, and their seed efficiency was within the species norm.

Evaluation of Mechanisms of Phosphorus Use Efficiency in Traditional Wheat Cultivars for Sustainable Cropping

In order to search for low input alternative wheat cultivars, this study aims to investigate the mechanisms of phosphorous (P) uptake and utilization efficiency of two traditional wheat cultivars as compared to a modern cultivar. The experiment was conducted under semi-controlled conditions using four P supplies. Plant growth and P efficiency parameters were studied at two harvest dates. Plant and soil parameters where measured: shoot dry matter, P concentration in shoot, root length, root diameter, specific root density, root length/shoot weight, shoot growth rate, P shoot demand on roots, P influx, P efficiency ratio, P utilization index, extractable and soil solution P concentrations, and P recovery. Traditional and modern cultivars had similar overall uptake (P influx, and recovery) and utilization efficiency. In terms of specific efficiency traits, traditional cultivars had the superiority in having more root size, higher root shoot ratio, slower shoot growth rate and less shoot demand on roots for P, but were inferior in having thicker roots and less specific root density. Investigating P use efficiency mechanisms could be a useful tool in selection programs to separate plant cultivars to superior and inferior, but using different measures of utilization efficiency parameters could be in some cases misleading.

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.

Investigations into the Causes and Control of theu Growth Arrestment Phenomenon of Sultana. I. Symptoms and Survey Results

Growth abnormalities, locally called arrestment phenomenon (GAP), occurring in the Sultana vineyards in the Lower Orange River region were first described in 1955. Characteristically, single vines or patches of vines are affected, show poor budding, retarded shoot growth during flowering, localised blackening of peduncles and abortion of flower clusters, followed by vigorous renewed shoot growth and flower shatter. Shiny spots on the upper surface of basal leaves are associated with symptoms mentioned above. Because of flower cluster abortion and flower shatter, crop losses exceeding 800/o occurred on affected vines. An extensive survey and analysis programme revealed GAP to be mainly associated with low K values in soil and plants, a low irrigation frequency, especially during the dormancy period, and relatively heavy textured soils.

Temporal and spatial changes in gene expression, metabolite accumulation and phytohormone content in rice seedlings grown under drought stress conditions.

In order to analyze the molecular mechanisms underlying the responses of plants to different levels of drought stress, we developed a soil matric potential (SMP)-based irrigation system that precisely controls soil moisture. Using this system, rice seedlings were grown under three different drought levels, denoted Md1, Md2 and Md3, with SMP values set to -9.8, -31.0 and -309.9 kPa, respectively. Although the Md1 treatment did not alter the visible phenotype, the Md2 treatment caused stomatal closure and shoot growth retardation (SGR). The Md3 treatment markedly induced SGR, without inhibition of photosynthesis. More severe drought (Sds) treatment, under which irrigation was terminated, resulted in the wilting of leaves and inhibition of photosynthesis. Metabolome analysis revealed the accumulation of primary sugars under Md3 and Sds and of most amino acids under Sds. The starch content was increased under Md3 and decreased under Sds. Transcriptome data showed that the expression profiles of associated genes supported the observed changes in photosynthesis and metabolites, suggesting that the time lag from SGR to inhibition of photosynthesis might lead to the accumulation of photosynthates under Md3, which can be used as osmolytes under Sds. To gain further insight into the observed SGR, transcriptome and hormonome analyses were performed in specific tissues. The results showed specific decreases in indole-3-acetic acid (IAA) and cytokinin levels in Md2-, Md3- and Sds-treated shoot bases, though the expression levels of hormone metabolism-related genes were not reflected in IAA and cytokinin contents. These observations suggest that drought stress affects the distribution or degradation of cytokinin and IAA molecules.

Early Measures of Drought Tolerance in Four Grape Rootstocks

Recent and severe droughts in major grape (Vitis)-growing regions of the United States and Australia underscore the importance of more efficient agricultural use of water. Grape rootstock breeding for increased drought tolerance could contribute to continued sustainable yields as fresh water supplies decline. Rhizotron containers were used in a greenhouse to investigate the predictive measures of drought tolerance in young grapevine rootstocks. Deeper rooting distributions were found for the drought-tolerant rootstocks ‘110R’ (Vitis berlandieri × Vitis rupestris) and ‘Ramsey’ (Vitis champinii, a natural hybrid of Vitis candicans × V. rupestris) as opposed to shallower distributions observed in the more drought-sensitive rootstocks ‘101-14Mgt’ (Vitis riparia × V. rupestris) and ‘Riparia Gloire’ (V. riparia). Production of new roots during a 6-day nonirrigated period declined 45% to 53% for ‘Riparia Gloire’ and ‘101-14Mgt’, respectively, but showed no change in ‘110R’ and ‘Ramsey’. Slow growth, a hallmark of abiotic stress tolerance, was evident in the drought-tolerant rootstocks in their relatively slow shoot growth before drought stress and their relatively slow new root growth during recovery, especially for ‘Ramsey’. High stomatal conductance (gS) corresponded with drought tolerance and distinguished rootstocks best during the first 3 days of recovery, with a mean value for ‘Ramsey’ 2.7 times higher than ‘101-14Mgt’. Stomatal conductance during recovery may serve as the most efficient means of predicting drought tolerance capacity in a breeding program.

System analysis of metabolism and the transcriptome in Arabidopsis thaliana roots reveals differential co-regulation upon iron, sulfur and potassium deficiency.

Deprivation of mineral nutrients causes significant retardation of plant growth. This retardation is associated with nutrient-specific and general stress-induced transcriptional responses. In this study, we adjusted the external supply of iron, potassium and sulfur to cause the same retardation of shoot growth. Nevertheless, limitation by individual nutrients resulted in specific morphological adaptations and distinct shifts within the root metabolite fingerprint. The metabolic shifts affected key metabolites of primary metabolism and the stress-related phytohormones, jasmonic, salicylic and abscisic acid. These phytohormone signatures contributed to specific nutrient deficiency-induced transcriptional regulation. Limitation by the micronutrient iron caused the strongest regulation and affected 18% of the root transcriptome. Only 130 genes were regulated by all nutrients. Specific co-regulation between the iron and sulfur metabolic routes upon iron or sulfur deficiency was observed. Interestingly, iron deficiency caused regulation of a different set of genes of the sulfur assimilation pathway compared with sulfur deficiency itself, which demonstrates the presence of specific signal-transduction systems for the cross-regulation of the pathways. Combined iron and sulfur starvation experiments demonstrated that a requirement for a specific nutrient can overrule this cross-regulation. The comparative metabolomics and transcriptomics approach used dissected general stress from nutrient-specific regulation in roots of Arabidopsis.

Witches’ broom and normal crown clones from the same trees of Pinus sibirica: a comparative morphological study

Mutational witches’ broom clones show a growth redistribution compared with normal clones. The main factor affecting the variations in mutant clone morphology is the strength of the mutation. Mutational witches’ broom is a fragment of the tree crown with abnormally dense branching and slower shoot growth, compared with those of a normal crown. Thousands of dwarf ornamental cultivars widely used in landscape design have been developed from mutational witches’ broom. In this study, crown morphology was compared between grafted clones of witches’ broom and normal clones from the same trees. The results quantify variations in crown structure between the mutants and normal clones. The sample materials were 10 pairs of grafted witches’ broom and normal crown clones of Pinus sibirica. The mutant and normal clones were discrete sets. Many morphological traits were affected in the mutants. Compared with the normal-crown clones, the mutants showed male sterility, decreased apical dominance, reduced shoot and needle length, and increased branching and seed cone bearing. In terms of morphogenic changes induced by the mutation, the shoots of the witches’ broom clones were bicyclic, generated seed cones that were much shorter than those of normal clones, and had acquired the ability to form lateral buds. The extent of interclonal variation was significantly greater among witches’ broom clones than among normal clones. Compared with the morphological traits of normal clones, those of the mutants were shifted in the same direction but to different extents. Therefore, mutational witches’ broom is the expression of a mutation that can be weak, medium, or strong. These results will be useful for unraveling the genetic basis of witches’ broom in conifers and for breeding new dwarf cultivars.

Control of shoot growth in Agrostemma githago L. by 4,4-dimethylmorpholinium chloride and related compounds

4,4-Dimethylmorpholinium chloride and (2-chloroethyl)-trimethylammonium chloride retarded shoot growth in &lt;i&gt;Agrostemma githago&lt;/i&gt; L. This effect was nullified by gibberellin. 4,4-Dimethyl-2-oxomorpholinium chloride and 4,4-diethyl-2-oxomorpholinium chloride slightly stimulated shoot growth.

Flower and leaf damage of grapevines caused by the grape rust mite, Calepitrimerus vitis (Nalepa)

The symptoms of damage on flower buds and leaves of grapevines caused by the grape rust mite, Calepitrimerus vitis (Nalepa) were examined in this study. The damaged flower buds displayed retarded growth and became dried up and some of the damaged flower clusters were curved. Not only symptom of damaged leaves such as malformed and bronzed leaves, but also retarded shoot growth was observed. Flower clusters (each flower cluster consisted of one main cluster and one side cluster) and leaves were collected to determine the relationship between degree of damage symptoms and density of the grape rust mite, which was measured by a modified washing and sieving method. The highest mean density (± SE) of C. vitis was found to be 672.6±112.9 per flower cluster with the mid-level damage, while the lowest mean density was found to be 327.6±55.5 per flower cluster with the high level damage. This was probably due to significant dispersal of grape rust mites from the highly damaged flower buds. Significantly higher numbers of C. vitis were found on the distorted leaves than on healthy ones.