FERONIA and microtubules independently contribute to mechanical integrity in the Arabidopsis shoot.

To survive, cells must constantly resist mechanical stress. In plants, this involves the reinforcement of cell walls, notably through microtubule-dependent cellulose deposition. How wall sensing might contribute to this response is unknown. Here, we tested whether the microtubule response to stress acts downstream of known wall sensors. Using a multistep screen with 11 mutant lines, we identify FERONIA (FER) as the primary candidate for the cell's response to stress in the shoot. However, this does not imply that FER acts upstream of the microtubule response to stress. In fact, when performing mechanical perturbations, we instead show that the expected microtubule response to stress does not require FER. We reveal that the feronia phenotype can be partially rescued by reducing tensile stress levels. Conversely, in the absence of both microtubules and FER, cells appear to swell and burst. Altogether, this shows that the microtubule response to stress acts as an independent pathway to resist stress, in parallel to FER. We propose that both pathways are required to maintain the mechanical integrity of plant cells.

Dioecious hemp (Cannabis sativa L.) plants do not express significant sexually dimorphic morphology in the seedling stage.

Some economically important crop species are dioecious, producing pollen and ovules on distinct, unisexual, individuals. On-the-spot diagnosis of sex is important to breeders and farmers for crop improvement and maximizing yield, yet diagnostic tools at the seedling stage are understudied and lack a scientific basis. Understanding sexual dimorphism in juvenile plants may provide key ecological, evolutionary and economic insights into dioecious plant species in addition to improving the process of crop cultivation. To address this gap in the literature, we asked: can we reliably differentiate males, females, and co-sexual individuals based on seedling morphology in Cannabis sativa, and do the traits used to distinguish sex at this stage vary between genotypes? To answer these questions, we collected data on phenotypic traits of 112 C. sativa plants (50 female, 52 male, 10 co-sexuals) from two hemp cultivars (CFX-1, CFX-2) during the second week of vegetative growth and used ANOVAs to compare morphology among sexes. We found males grew significantly longer hypocotyls than females by week 2, but this difference depended on the cultivar investigated. Preliminary evidence suggests that co-sexual plants may be distinguished from male and female plants using short hypocotyl length and seedling height, although this relationship requires more study since sample sizes of co-sexual plants were small. In one of the cultivars, two-week old male plants tend to produce longer hypocotyls than other plants, which may help to identify these plants prior to anthesis. We call for increased research effort on co-sexual plants, given their heavy economic cost in industrial contexts and rare mention in the literature. Our preliminary data suggests that short hypocotyl length may be an indicator of co-sexuality. These results are the first steps towards developing diagnostic tools for predicting sex using vegetative morphology in dioecious species and understanding how sexual dimorphism influences phenotype preceding sexual maturity.

Phenotypic Study of Photomorphogenesis in Arabidopsis Seedlings.

Light is one of the most important environmental factors, serving as the energy source of photosynthesis and a cue for plant developmental programs, called photomorphogenesis. Here, we provide a standardized operation to measure physiological parameters of photomorphogenesis, including in hypocotyl length, cotyledon size, and anthocyanin content.

Method for Phenotypic Chemical Screening to Identify Cryptochrome Inhibitors.

After germination, plants determine their morphogenesis, such as hypocotyl elongation and cotyledon opening, by responding to various wavelengths of light (photomorphogenesis). Cryptochrome is a blue-light photoreceptor that controls de-etiolation, stomatal opening and closing, flowering time, and shade avoidance. Successful incorporation of these phenotypes as indicators into a chemical screening system results in faster selection of candidate compounds. Here, we describe phenotypic screening for the blue-light response of Arabidopsis thaliana seedling and the resulting process that clarifies that the compound obtained in the screening is an inhibitor of cryptochromes.

AtHDA15 binds directly to COP1 positively regulating photomorphogenesis.

Reversible histone acetylation and deacetylation play crucial roles in modulating light-regulated gene expression during seedling development. However, it remains largely unknown how histone-modifying enzymes interpose within the molecular framework of light signaling network. In this study, we show that AtHDA15 positively regulates photomorphogenesis by directly binding to COP1, a master regulator in the repression of photomorphogenesis. hda15 T-DNA knock-out and RNAi lines exhibited light hyposensitivity with reduced HY5 and PIF3 protein levels leading to long hypocotyl phenotypes in the dark while its overexpression leads to increased HY5 concentrations and short hypocotyl phenotypes. In vivo and in vitro binding assays show that HDA15 directly interacts with COP1 inside the nucleus modulating COP1's repressive activities. As COP1 is established to act within the nucleus to regulate specific transcription factors associated with growth and development in skotomorphogenesis, the direct binding by HDA15 is predicted to abrogate activities of COP1 in the presence of light and modulate its repressive activities in the dark. Our results append the mounting evidence for the role of HDACs in post-translational regulation in addition to their well-known histone modifying functions.

Enhanced thermotolerance of Arabidopsis by chitooligosaccharides-induced CERK1n-ERc fusion gene.

Heat stress is a major growth-limiting factor for most crops over the world. Chitin elicitor receptor kinase 1 (CERK1) is a chitin/chitooligosaccharides receptor, and ERECTA (ER) plays a crucial role in plant resistance to heat stress. In the present study, a chitooligosaccharides-induced CERK1n-ERc fusion gene was designed and synthesized, in which the extracellular domain and transmembrane domain of CERK1 gene is connected with the response region of ER gene. We successfully constructed the CERK1n-ERc fusion gene by Overlap PCR and introduced it into Arabidopsis by Agrobacterium-medicated infection. Genetically modified (GM) plants had a greater germination rate and germination index, as well as a shorter mean germination time, indicating that they had a better thermotolerance compared with the wild-type (WT) lines under heat stress. Moreover, the GM lines showed a lower level of hydrogen peroxide (H2O2) and relative electrolyte leakage (REL), suggesting that they were in better state compared with the WT plants when exposed to high temperature. UPLC-MS/MS was employed to assess the phytohormone level, suggesting that the GM lines acquired a better thermotolerance via jasmonic acid (JA) signaling pathways. In general, we constructed a COS-induced fusion gene to enhance the thermotolerance of Arabidopsis during seed germination and postgermination growth.

Seed-specific down-regulation of Arabidopsis CELLULOSE SYNTHASE 1 or 9 reduces seed cellulose content and differentially affects carbon partitioning.

KEY MESSAGE: Seed-specific down-regulation of AtCESA1 and AtCESA9, which encode cellulose synthase subunits, differentially affects seed storage compound accumulation in Arabidopsis. High amounts of cellulose can negatively affect crop seed quality, and, therefore, diverting carbon partitioning from cellulose to oil, protein and/or starch via molecular breeding may improve seed quality. To determine the effect of seed cellulose content reduction on levels of storage compounds, Arabidopsis thaliana CELLULOSE SYNTHASE1 (AtCESA1) and AtCESA9 genes, which both encode cellulose synthase subunits, were individually down-regulated using seed-specific intron-spliced hairpin RNA (hpRNAi) constructs. The selected seed-specific AtCESA1 and AtCESA9 Arabidopsis RNAi lines displayed reduced cellulose contents in seeds, and exhibited no obvious visual phenotypic growth defects with the exception of a minor effect on early root development in AtCESA1 RNAi seedlings and early hypocotyl elongation in the dark in both types of RNAi line. The seed-specific down-regulation of AtCESA9 resulted in a reduction in seed weight compared to empty vector controls, which was not observed in AtCESA1 RNAi lines. In terms of effects on carbon partitioning, AtCESA1 and AtCESA9 RNAi lines exhibited distinct effects. The down-regulation of AtCESA1 led to a ~ 3% relative increase in seed protein content (P = 0.04) and a ~ 3% relative decrease in oil content (P = 0.02), but caused no alteration in soluble glucose levels. On the contrary, AtCESA9 RNAi lines did not display a significant reduction in seed oil, protein or soluble glucose content. Taken together, our results indicate that the seed-specific down-regulation of AtCESA1 causes alterations in seed storage compound accumulation, while the effect of AtCESA9 on carbon partitioning is absent or minor in Arabidopsis.

A Deep Learning-Based Approach for High-Throughput Hypocotyl Phenotyping.

Hypocotyl length determination is a widely used method to phenotype young seedlings. The measurement itself has advanced from using rulers and millimeter papers to assessing digitized images but remains a labor-intensive, monotonous, and time-consuming procedure. To make high-throughput plant phenotyping possible, we developed a deep-learning-based approach to simplify and accelerate this method. Our pipeline does not require a specialized imaging system but works well with low-quality images produced with a simple flatbed scanner or a smartphone camera. Moreover, it is easily adaptable for a diverse range of datasets not restricted to Arabidopsis (Arabidopsis thaliana). Furthermore, we show that the accuracy of the method reaches human performance. We not only provide the full code at https://github.com/biomag-lab/hypocotyl-UNet, but also give detailed instructions on how the algorithm can be trained with custom data, tailoring it for the requirements and imaging setup of the user.

Molecular analysis of anthocyanin biosynthesis-related genes reveal BoTT8 associated with purple hypocotyl of broccoli (Brassica oleracea var. italica L.).

Broccoli (Brassica oleracea var. italica L.) is a highly nutritious vegetable that typically forms pure green or purple florets. However, green broccoli florets sometimes accumulate slight purplish pigmentation in response environmental factors, decreasing their market value. In the present study, we aimed to develop molecular markers to distinguish broccoli genotypes as pure green or purplish floret color at the early seedling stage. Anthocyanins are known to be involved in the purple pigmentation in plants. The purplish broccoli lines were shown to accumulate purple pigmentation in the hypocotyls of very young seedlings; therefore, the expression profiles of the structural and regulatory genes of anthocyanin biosynthesis were analyzed in the hypocotyls using qRT-PCR. BoPAL, BoDFR, BoMYB114, BoTT8, BoMYC1.1, BoMYC1.2, and BoTTG1 were identified as putative candidate genes responsible for the purple hypocotyl color. BoTT8 was much more highly expressed in the purple than green hypocotyls; therefore, it was cloned and sequenced from various broccoli lines, revealing SNP and InDel variations between these genotypes. We tested four SNPs (G > A; A > T; G > C; T > G) in the first three exons and a 14-bp InDel (ATATTTATATATAT) in the BoTT8 promoter in 51 broccoli genotypes, and we found these genetic variations could distinguish the green lines, purple lines, and F1 hybrids. These novel molecular markers could be useful in broccoli breeding programs to develop a true green or purple broccoli cultivar.

Co-optimization of axial root phenotypes for nitrogen and phosphorus acquisition in common bean.

Background and Aims: Root architecture is a primary determinant of soil resource acquisition. We hypothesized that root architectural phenes will display both positive and negative interactions with each other for soil resource capture because of competition for internal resources and functional trade-offs in soil exploration. Methods: We employed the functional-structural plant model SimRoot to explore how interactions among architectural phenes in common bean determine the acquisition of phosphate and nitrate, two key soil resources contrasting in mobility. We evaluated the utility of basal root whorl number (BRWN) when basal root growth angle, hypocotyl-borne roots and lateral root branching density (LRBD) were varied, under varying availability of phosphate and nitrate. Key Results: Three basal root whorls were optimal in most phenotypes. This optimum shifted towards greater values when LRBD decreased and to smaller numbers when LRBD increased. The maximum biomass accumulated for a given BRWN phenotype in a given limiting nutrient scenario depended upon root growth angle. Under phosphorus stress shallow phenotypes grew best, whereas under nitrate stress fanned phenotypes grew best. The effect of increased hypocotyl-borne roots depended upon BRWN as well as the limiting nutrient. Greater production of axial roots due to BRWN or hypocotyl-borne roots reduced rooting depth, leading to reduced biomass under nitrate-limiting conditions. Increased BRWN as well as greater LRBD increased root carbon consumption, resulting in reduced shoot biomass. Conclusions: We conclude that the utility of a root architectural phenotype is determined by whether the constituent phenes are synergistic or antagonistic. Competition for internal resources and trade-offs for external resources result in multiple phenotypes being optimal under a given nutrient regime. We also find that no single phenotype is optimal across contrasting environments. These results have implications for understanding plant evolution and also for the breeding of more stress-tolerant crop phenotypes.

Sucrose supply from leaves is required for aerenchymatous phellem formation in hypocotyl of soybean under waterlogged conditions.

Background and Aims: Soil waterlogging often causes oxygen deficiency in the root systems of plants and severely inhibits plant growth. Formation of aerenchyma - interconnected spaces that facilitate the movement of gases between and within the aerial and submerged parts of plants - is an adaptive trait for coping with waterlogged conditions. Soybean (Glycine max) forms porous secondary tissues known as aerenchymatous phellem (AP), which are derived from the outermost cell layer of phellogen. To understand what factors other than waterlogging are involved in phellogen and AP formation, we examined how their formation in soybean seedlings was affected by darkness, CO2 deficiency and blockage of phloem transport. Methods: Aerenchymatous phellem and phellogen formation were expressed as area ratios in cross-sections of hypocotyl. CO2 was depleted by use of calcium oxide and sodium hydroxide. Phloem transport was blocked by heat-girdling of hypocotyls. Sucrose levels were measured by spectrophotometry. Key Results: Under light conditions, waterlogging induced the accumulation of high concentrations of sucrose in hypocotyls, followed by phellogen and AP formation in hypocotyls. Phellogen formation and AP formation were inhibited by darkness, CO2 deficiency and blockage of phloem transport. Phellogen formation and AP formation were also inhibited by excision of shoots above the epicotyl, but they recovered following application of sucrose (but not glucose or fructose application) to the cut surface. Conclusions: The results demonstrate that sucrose derived from leaves is essential for AP and phellogen formation in soybean hypocotyls under waterlogged soil conditions. Maintenance of a high sucrose concentration is thus essential for the development of phellogen and AP and the differentiation of phellogen to AP.

Modification of growth anisotropy and cortical microtubule dynamics in Arabidopsis hypocotyls grown under microgravity conditions in space.

We carried out a space experiment, denoted as Aniso Tubule, to examine the effects of microgravity on the growth anisotropy and cortical microtubule dynamics in Arabidopsis hypocotyls, using lines in which microtubules are visualized by labeling tubulin or microtubule-associated proteins (MAPs) with green fluorescent protein (GFP). In all lines, GFP-tubulin6 (TUB6)-, basic proline-rich protein1 (BPP1)-GFP- and spira1-like3 (SP1L3)-GFP-expressing using a constitutive promoter, and spiral2 (SPR2)-GFP- and GFP-65 kDa MAP-1 (MAP65-1)-expressing using a native promoter, the length of hypocotyls grown under microgravity conditions in space was longer than that grown at 1 g conditions on the ground. In contrast, the diameter of hypocotyls grown under microgravity conditions was smaller than that of the hypocotyls grown at 1 g. The percentage of cells with transverse microtubules was increased under microgravity conditions, irrespective of the lines. Also, the average angle of the microtubules with respect to the transverse cell axis was decreased in hypocotyls grown under microgravity conditions. When GFP fluorescence was quantified in hypocotyls of GFP-MAP65-1 and SPR2-GFP lines, microgravity increased the levels of MAP65-1, which appears to be involved in the maintenance of transverse microtubule orientation. However, the levels of SPR2 under microgravity conditions were comparable to those at 1 g. These results suggest that the microgravity-induced increase in the levels of MAP65-1 is involved in increase in the transverse microtubules, which may lead to modification of growth anisotropy, thereby developing longer and thinner hypocotyls under microgravity conditions in space.

Ontogenesis and functions of saxophone stem in Acrocomia aculeata (Arecaceae).

BACKGROUND AND AIMS: The underground saxophone stem systems produced by seedlings of certain palm species show peculiar growth patterns and distinctive morphologies, although little information is available concerning their development and function. We studied the ontogenesis of the saxophone stem in Acrocomia aculeata, an important neotropical oleaginous palm, and sought to experimentally define its function. METHODS: Morpho-anatomical evaluations were performed during 240 d on seedlings using traditional methodologies. The tuberous region of the structure was submitted to histochemical tests and evaluated by transmission electron microscopy. The aerial portions of 130 1- to 3-year-old greenhouse plants were removed and their continuous growth capacity was evaluated after 30 d. Severed saxophone stems were also stored at room temperature (average 25 °C) for up to 90 d and then cultured for 60 d to evaluate root and shoot emission. KEY RESULTS: The development of the saxophone stem is distinct from other underground systems previously described, and involves three processes: growth and curvature of the cotyledonary petiole, expansion and curvature of the hypocotyl, and expansion of the plumule internodes. The tuberous region stores water and starch, as well as lesser amounts of mucilage and oil. Growth of the aerial portion occurred in 84 % of the separated saxophone stems and in 53 % of the stems held in storage. CONCLUSIONS: The saxophone stem represents an important adaptation of A. aculeata to anthropogenically impacted and/or dry environments by promoting the burial of both the shoot meristem and storage reserves, which allows the continuous growth of aerial organs.

Cambios anatómicos en raíces e hipocótilos de plántulas de Prosopis ruscifolia (Fabaceae) sometidas a estrés salino / Anatomical changes in roots and hypocotyls of Prosopis ruscifolia (Fabaceae) seedlings exposed to saline stress

ResumenProsopis ruscifolia es una especie arbórea pionera en áreas inundadas o salinas. El objetivo de este trabajo fue determinar cambios anatómicos en raíces e hipocótilos de plántulas de P. ruscifolia sometidas a estrés salino, bajo condiciones controladas. Las semillas se recolectaron en bosques nativos de la Región Chaqueña Occidental de Argentina. Las semillas se sembraron sobre toallas de papel humedecidas con soluciones salinas de 100, 200 y 300 mM de NaCl y un control humedecido con agua destilada. Se sembraron cuatro repeticiones de 50 semillas cada una, correspondientes a cada tratamiento, se ubicaron en cajas plásticas herméticas dentro de cámara de siembra a 27 ºC y con fotoperíodo de 12 horas. Doce días después de la siembra, se extrajeron plántulas para estudios anatómicos. Se estudiaron 35 plántulas correspondientes a cada tratamiento. Se midieron en raíces e hipocótilos las siguientes variables anatómicas: diámetro de la raíz principal e hipocótilo (µm), espesor de la corteza (µm), número de estratos celulares en la corteza, diámetro del cilindro central (µm), diámetro de la médula (µm), número de estratos celulares en el periciclo y diámetro tangencial de los vasos (µm). Se realizó ANOVA con diámetro de la raíz o hipocótilo como variable dependiente y espesor de la corteza, número de estratos celulares en la corteza, diámetro del cilindro central, diámetro de la médula, número de estratos celulares en el periciclo, diámetro tangencial de los vasos y concentración salina como variables independientes. El diámetro de la raíz disminuyó significativamente con el aumento de la concentración salina (P < 0.0001). El espesor de la corteza redujo su espesor a 100 mM (P < 0.0001) e incrementó el número de estratos celulares que la componen (P < 0.0002). El diámetro del cilindro central se redujo a la concentración salina de 100 mM (P < 0.0001) y el diámetro de la médula y el número de estratos celulares del periciclo (P < 0.0003) disminuyó progresivamente hasta 300 mM. El diámetro tangencial de los vasos (P < 0.0001) se redujo recién a 300 mM de NaCl. Estos cambios anatómicos podrían estar relacionados con la alteración de la expansión y división celular causada por la salinidad y comprometer la formación de raíces laterales y el almacenamiento de reservas. Los hipocótilos no mostraron cambios anatómicos significativos en respuesta al incremento en la salinidad, con excepción de la variación en la posición de estomas y un incremento en el espesor de la hipodermis. Estos cambios parecen indicar el estrés hídrico impuesto por el bajo potencial osmótico causado por las sales. Las plántulas de P. ruscifolia experimentaron cambios anatómicos en respuesta a las concentraciones salinas analizadas, en rasgos vinculados al almacenamiento de reservas, a la absorción y la conducción de agua y la formación de raíces laterales.

Abstract:Prosopis ruscifolia is a pioneer tree species in flooding or saline areas. The aim of this work was to assess anatomical changes in roots and hypocotyls of P. ruscifolia seedlings induced to saline stress under controlled conditions. Seeds, collected in natural forests of Western Chaco region in Argentina, were sown on paper towels moisturized with saline solutions of 100, 200 and 300 mM of NaCl, and a control group with distilled water. Four repetitions of 50 seeds per treatment were sown, located in hermetic polystyrene boxes, and included in a seeding chamber, at 27 ºC and 12 hours photoperiod. Were studied 35 seedlings from each saline concentration; these seedlings were processed 12 days after sown to obtain microscopic samples. The anatomical variables measured in roots and hypocotyls were the following: main root diameter (µm), bark thickness (µm), number of cell strata in bark, central cylinder diameter (µm), pith diameter (µm), number of cell strata in the pericycle and the tangential diameter of vessels (µm). ANOVA analysis were performed with hypocotyl and root diameters as the dependent variable, and bark thickness (µm), number of cell strata in the bark, the central cylinder diameter (µm), the pith diameter (µm), number of cell strata in the pericycle, the tangential diameter of vessels and the saline concentration as independent variables. Results showed that the root diameter decreased with increasing saline concentrations (P < 0.0001). The bark thickness decreased at 100 mM (P < 0.0001) and the number of cell strata of bark increased to 300 mM (P < 0.0002). The central cylinder diameter decreased at 100 mM saline concentration (P < 0.0001) and the number of cell strata of the pericycle and the pith diameter reduced progressively until 300 mM. The tangential diameter of vessels decreased at 300 mM. These anatomical changes suggested alterations in the expansion and cell division caused by the salinity, and could limit lateral roots formation and reserves storage. Hypocotyls did not show significant anatomical changes in response to increasing salinity, with exception of stomata position and an increase of the hypodermis thickness. These changes indicated that the water stress imposed by low osmotic potential is caused by increasing saline concentration. The seedlings of P. ruscifolia experienced anatomical changes in response to tested saline concentrations in traits related to reserve storage, the absorption and conduction of water, and lateral roots formation. Rev. Biol. Trop. 64 (3): 1007-1017. Epub 2016 September 01.

DELLA-mediated PIF degradation contributes to coordination of light and gibberellin signalling in Arabidopsis.

Light and gibberellins (GAs) antagonistically regulate hypocotyl elongation in plants. It has been demonstrated that DELLAs, which are negative regulators of GA signalling, inhibit phytochrome-interacting factors 3 and 4 (PIF3 and PIF4) by sequestering their DNA-recognition domains. However, it is unclear whether there are other mechanisms of regulatory crosstalk between DELLAs and PIFs. Here, we demonstrate that DELLAs negatively regulate the abundance of four PIF proteins through the ubiquitin-proteasome system. Reduction of PIF3 protein abundance by DELLAs correlates closely with reduced hypocotyl elongation. Both sequestration and degradation of PIF3 by DELLAs contribute to a reduction in PIF3 binding to its target genes. Thus, we show that promotion of PIF degradation by DELLAs is required to coordinate light and GA signals, and the dual regulation of transcription factors by DELLAs by both sequestration and degradation may be a general mechanism.

Root development and structure in seedlings of Ginkgo biloba.

PREMISE OF THE STUDY: The popular, highly recognizable, well-known gymnosperm, Ginkgo biloba, was studied to document selected developmental features, which are little known in its primary root system from root tips to cotyledonary node following seed germination. METHODS: Using seedlings grown in soil, vermiculite, or a mixture, we examined sections at various distances from the root cap to capture a developmental sequence of anatomical structures by using standard brightfield, epifluorescence, and confocal microscopic techniques. KEY RESULTS: The vascular cylinder is usually a diarch stele, although modified diarchy and triarchy are found. Between exarch protoxylem poles, metaxylem usually develops into a complete disc, except near the transition region, which has irregularly arranged tracheary cells. The disc of primary xylem undergoes secondary growth on its metaxylem flanks with many tracheids added radially within a few weeks. Production of fibers in secondary phloem also accompanies secondary growth. In the cortex, endodermis produces Casparian bands early in development and continues into the upper transition region. Phi cells with phi-thickenings (bands of lignified walls) of a layer of inner cortex are often evident before endodermis, and then adjoining, additional layers of cortex develop phi cells; phi cells do not occur in the upper transition region or stem. An exodermis is produced early in root development and is continuous into the transition region and cotyledonary node. CONCLUSIONS: Seedling root axes of Ginkgo biloba are more complex than the literature suggests, and our findings contribute to our knowledge of root structure of this ancient gymnosperm.

[Anatomical changes in roots and hypocotyls of Prosopis ruscifolia (Fabaceae) seedlings exposed to saline stress].

Prosopis ruscifolia is a pioneer tree species in flooding or saline areas. The aim of this work was to assess anatomical changes in roots and hypocotyls of P. ruscifolia seedlings induced to saline stress under controlled conditions. Seeds, collected in natural forests of Western Chaco region in Argentina, were sown on paper towels moisturized with saline solutions of 100, 200 and 300 mM of NaCl, and a control group with distilled water. Four repetitions of 50 seeds per treatment were sown, located in hermetic polystyrene boxes, and included in a seeding chamber, at 27 ºC and 12 hours photoperiod. Were studied 35 seedlings from each saline concentration; these seedlings were processed 12 days after sown to obtain microscopic samples. The anatomical variables measured in roots and hypocotyls were the following: main root diameter (µm), bark thickness (µm), number of cell strata in bark, central cylinder diameter (µm), pith diameter (µm), number of cell strata in the pericycle and the tangential diameter of vessels (µm). ANOVA analysis were performed with hypocotyl and root diameters as the dependent variable, and bark thickness (µm), number of cell strata in the bark, the central cylinder diameter (µm), the pith diameter (µm), number of cell strata in the pericycle, the tangential diameter of vessels and the saline concentration as independent variables. Results showed that the root diameter decreased with increasing saline concentrations (P < 0.0001). The bark thickness decreased at 100 mM (P < 0.0001) and the number of cell strata of bark increased to 300 mM (P < 0.0002). The central cylinder diameter decreased at 100 mM saline concentration (P < 0.0001) and the number of cell strata of the pericycle and the pith diameter reduced progressively until 300 mM. The tangential diameter of vessels decreased at 300 mM. These anatomical changes suggested alterations in the expansion and cell division caused by the salinity, and could limit lateral roots formation and reserves storage. Hypocotyls did not show significant anatomical changes in response to increasing salinity, with exception of stomata position and an increase of the hypodermis thickness. These changes indicated that the water stress imposed by low osmotic potential is caused by increasing saline concentration. The seedlings of P. ruscifolia experienced anatomical changes in response to tested saline concentrations in traits related to reserve storage, the absorption and conduction of water, and lateral roots formation.

Potential of hypocotyl diameter in family selection aiming at plant architecture improvement of common bean.

Cultivars of common bean with more erect plant architecture and greater tolerance to degree of lodging are required by producers. Thus, to evaluate the potential of hypocotyl diameter (HD) in family selection for plant architecture improvement of common bean, the HDs of 32 F2 plants were measured in 3 distinct populations, and the characteristics related to plant architecture were analyzed in their progenies. Ninety-six F2:3 families and 4 controls were evaluated in a randomized block design, with 3 replications, analyzing plant architecture grade, HD, and grain yield during the winter 2010 and drought 2011 seasons. We found that the correlation between the HD of F2 plants and traits related to plant architecture of F2:3 progenies were of low magnitude compared to the estimates for correlations considering the parents, indicating a high environmental influence on HD in bean plants. There was a predominance of additive genetic effects on the determination of hypocotyl diameter, which showed higher precision and accuracy compared to plant architecture grade. Thus, this characteristic can be used to select progenies in plant architecture improvement of common beans; however, selection must be based on the means of at least 39 plants in the plot, according to the results of repeatability analysis.

Effect of Environmental Factors on Germination and Emergence of Invasive Rumex confertus in Central Europe.

Rumex confertus is a biennial species native to Eastern Europe and Asia, where it thrives on meadow-steppes and glades in forest-steppe. This species has increased its range rapidly within central Europe, yet its biology is not well understood, which has led to poorly timed management. Effects of temperature, light, sodium chloride (NaCl), hydrogen ion concentration (pH), potassium nitrate (KNO3), and polyethylene glycol 6000 on seed germination were examined. Seedling emergence was examined for seeds sown at different depths in sand-filled pots. Seeds of R. confertus were nondormant at maturity. The germination percentage and rate of germination were significantly higher in light than in darkness. Secondary dormancy was induced in these seeds by 12 weeks of dark incubation at 4°C. The seeds of R. confertus undergo a seasonal dormancy cycle with deep dormancy in winter and early spring and a low level of dormancy in early autumn. Germination decreased as soil salinity increased. NO3(-) increased the percentage and rate of germination in the studied species. Decrease in seedling emergence from the seeds buried at >0.5 cm may be due to deficiency of light. From our experiments, we conclude that the weed R. confertus normally becomes established in vegetation gaps or due to disturbance of the uppermost soil layer during the growing season through the germination of seeds originating from a long-lived seed bank.

Manipulation of the hypocotyl sink activity by reciprocal grafting of two Raphanus sativus varieties: its effects on morphological and physiological traits of source leaves and whole-plant growth.

To reveal whether hypocotyl sink activities are regulated by the aboveground parts, and whether physiology and morphology of source leaves are affected by the hypocotyl sink activities, we conducted grafting experiments using two Raphanus sativus varieties with different hypocotyl sink activities. Comet (C) and Leafy (L) varieties with high and low hypocotyl sink activities were reciprocally grafted and resultant plants were called by their scion and stock such as CC, LC, CL and LL. Growth, leaf mass per area (LMA), total non-structural carbohydrates (TNCs) and photosynthetic characteristics were compared among them. Comet hypocotyls in CC and LC grew well regardless of the scions, whereas Leafy hypocotyls in CL and LL did not. Relative growth rate was highest in LL and lowest in CC. Photosynthetic capacity was correlated with Rubisco (ribulose 1·5-bisphosphate carboxylase/oxygenase) content but unaffected by TNC. High C/N ratio and accumulation of TNC led to high LMA and structural LMA. These results showed that the hypocotyl sink activity was autonomously regulated by hypocotyl and that the down-regulation of photosynthesis was not induced by TNC. We conclude that the change in the sink activity alters whole-plant growth through the changes in both biomass allocation and leaf morphological characteristics in R. sativus.