Differences In Germination Rates Research Articles

OsNAL11 and OsGASR9 Regulate the Low-Temperature Germination of Rice Seeds by Affecting GA Content

Low temperatures cause serious threat to rice seed emergence, which has become one of the main limiting factors in the production of direct seeding rice. It is of great importance to study the genes controlling low-temperature tolerance during seed germination and to mine the possible regulatory mechanism for developing new rice varieties with immense low-temperature germination ability. In the current research study, two types of mutants of nal11 and gasr9, derived from the WT (wild type) ZH11, were used for the analysis of low-temperature germinability. The results showed that the nal11 and gasr9 mutants displayed no significant difference in germination rate with ZH11 at room temperature, but the mutants showed significantly lower germination rates, germination potential and germination index, and slowed seedling growth in the simulated direct seeding experiments at low temperatures compared to ZH11. Additionally, the activity of POD, SOD, CAT, and anti-superoxide anion radial activity were significantly reduced, but the levels of MDA and H2O2 were significantly higher in the nal11 and gasr9 mutant seeds that were germinated at low temperatures compared to ZH11. Further analysis revealed that the levels of total active GA, especially GA4 and GA7, were significantly lower in the nal11 and gasr9 mutants than that in ZH11 during low-temperature germination. Based on qRT-PCR analysis, the expression levels of some GA synthesis-related genes were higher, whereas some were lower in the nal11 and gasr9 mutants than those in ZH11, however, the GA metabolism-related genes OsGA2ox8 and OsGA2ox10 and the GA signaling negative regulator gene SLR1 were significantly up-regulated in both nal11 and gasr9 mutants at several time points during low-temperature germination. This may explain the lower GA levels in the nal11 and gasr9 mutants. Furthermore, the interaction between the OsNAL11 and OsGASR9 proteins was confirmed by Y2H, LUC, and Co-IP assays. This study provides preliminary insights into the regulatory mechanism of the OsNAL11 and OsGASR9 genes, which control the low-temperature germination of rice seeds by affecting the GA pathway. Our study will provide the basis for further mining the molecular mechanisms of low-temperature germination in rice and valuable theoretical reference for breeding varieties with strong low-temperature germinability.

Integration of mRNA-miRNA Reveals the Possible Role of PyCYCD3 in Increasing Branches Through Bud-Notching in Pear (Pyrus bretschneideri Rehd.).

Bud-notching in pear varieties with weak-branches enhances branch development, hormone distribution, and germination, promoting healthier growth and improving early yield. To examine the regulatory mechanisms of endogenous hormones on lateral bud germination in Pyrus spp. (cv. 'Huangguan') (Pyrus bretschneideri Rehd.), juvenile buds were collected from 2-year-old pear trees. Then, a comprehensive study, including assessments of endogenous hormones, germination and branching rates, RNA-seq analysis, and gene function analysis in these lateral buds was conducted. The results showed that there was no significant difference in germination rate between the control and bud-notching pear trees, but the long branch rate was significantly increased in bud-notching pear trees compared to the control (p < 0.05). After bud-notching, there was a remarkable increase in IAA and BR levels in the pruned section of shoots, specifically by 141% and 93%, respectively. However, the content of ABA in the lateral buds after bud-notching was not significantly different from the control. Based on RNA-seq analysis, a notable proportion of the differentially expressed genes (DEGs) were linked to the plant hormone signal transduction pathway. Notably, the brassinosteroid signaling pathway seemed to have the closest connection with the branching ability of pear with the related genes encoding BRI1 and CYCD3, which showed significant differences between lateral buds. Finally, the heterologous expression of PyCYCD3 has a positive regulatory effect on the increased Arabidopsis growth and branching numbers. Therefore, the PyCYCD3 was identified as an up-regulated gene that is induced via brassinosteroid (BR) and could act as a conduit, transforming bud-notching cues into proliferative signals, thereby governing lateral branching mechanisms in pear trees.

Comparison of Juvenile Development of Maize and Sorghum in Six Temperate Soil Types under Extreme Water Regimes

Climate change requires the introduction of alternative crops in certain temperate areas due to the warmer and drier growing seasons. Maize, one of the most important crops, is projected to become less tolerant of a drier climate. Therefore, it is necessary to find an alternative species that is less susceptible to environmental stressors. This study compared the germination, growth vigour, and stress tolerance of maize and sorghum grow in six types of soil under three water regimes. The results indicate that sorghum germination is faster and more uniform. The most significant differences in germination rates were found in chernozem (88.9% and 72.2% for sorghum and maize, respectively) and saline solonetz (74.4% and 63.3% for sorghum and maize, respectively). Maize exhibited higher growth vigour only in three cases, i.e., under solonetz–flooding, shifting sand–drought, and brown forest floor–flooding conditions. An ANOVA showed a significant difference between sorghum and maize stress conditions due to soil conditions and water availability (p &lt; 0.0001). Sorghum can be a suitable alternative to maize, but only in areas with hot, dry periods and in areas where the soil is not too prone to waterlogging, regardless of its quality.

Low temperature and excess moisture affect seed germination of soybean (Glycine max L.) under controlled environments

Cold and excess moisture pose a serious threat to soybean production especially during seed germination in short-season environments. In this study, the effects of low temperature and excess moisture stress on seed germination were investigated in 187 soybean accessions originating from 18 countries. The experiment used a combination of three temperature conditions (i.e., 20 °C/14 °C, 14 °C/10 °C, and 10 °C/10 °C day/night) and two moisture levels (i.e., normal and excess). The seed germinability traits measured included germination rate (GR), germination index, germination time, germination uniformity, and coefficient of velocity of germination. Overall, GR was lowest in the 20 °C/14 °C + excess moisture and germination time was longest in the 10 °C/10 °C + excess moisture. When compared with 20 °C/14 °C + normal moisture treatment, GR at 10 °C/10 °C + excess moisture decreased by 38%; germination time increased by 20 days; seed viability decreased by 83%; germination uniformity decreased by 70%; germination speed decreased by 73%. Differences in GR, germination index, and germination velocity under different treatments were affected by temperature, moisture, and their interaction. Variation in germination time uniformity was determined by temperature, with no significant effects of moisture conditions and the interaction of temperature and moisture. It was shown that the temperature–excess moisture interaction led to a sharp decrease in seed germination. Two genotypes including PI 603147 and PI 507702 were identified with a GR over 90% at 10 °C/10 °C + excess moisture. This study generated new knowledge and data to further the understanding of genetic resistance to cold and excess moisture stress in soybean.

Boron homeostasis affects Longan yield: a study of NIP and BOR boron transporter of two cultivars

BackgroundEssential micronutrient Boron (B) plays crucial roles in plant survival and reproduction but becomes toxic in higher quantities. Although plant cells have different B transport systems, B homeostasis is mainly maintained by two transporter protein families: B exporters (BOR) and nodulin-26-like intrinsic proteins (NIP). Their diversity and differential expression are responsible for varied B tolerance among plant varieties and species. Longan is a highly admired subtropical fruit with a rising market in China and beyond. In the present study, we cultured Shixia (SX) and Yiduo (YD), two differently characterized Longan cultivars, with foliar B spray. We analyzed their leaf physiology, fruit setting, B content, and boron transporter gene expression of various tissue samples. We also traced some of these genes' subcellular localization and overexpression effects.ResultsYD and SX foliage share similar microstructures, except the mesophyll cell wall thickness is double in YD. The B spray differently influenced their cellular constituents and growth regulators. Gene expression analysis showed reduced BOR genes expression and NIP genes differential spatiotemporal expression. Using green fluorescent protein, two high-expressing NIPs, NIP1 and NIP19, were found to translocate in the transformed tobacco leaves' cell membrane. NIPs transformation of SX pollen was confirmed using magnetic beads and quantified using a fluorescence microscope and polymerase chain reaction. An increased seed-setting rate was observed when YD was pollinated using these pollens. Between the DlNIP1 and DlNIP19 transformed SX pollen, the former germinated better with increasing B concentrations and, compared to naturally pollinated plants, had a better seed-setting rate in YD♀ × SX♂.ConclusionSX and YD Longan have different cell wall structures and react differently to foliar B spray, indicating distinct B tolerance and management. Two B transporter NIP genes were traced to localize in the plasma membrane. However, under high B concentrations, their differential expression resulted in differences in Jasmonic acid content, leading to differences in germination rate. Pollination of YD using these NIPs transformed SX pollen also showed NIP1 overexpression might overcome the unilateral cross incompatibility between YD♀ × SX♂ and can be used to increase Longan production.

Transcriptome atlas of Striga germination: Implications for managing an intractable parasitic plant

Societal Impact StatementWitchweeds, parasitic plants of the genus Striga, are nicknamed “cereal killers” because of their devastating destruction of Africa's most staple cereals, including maize, sorghum, millets, and upland rice. The parasite relies on biomolecules emitted from the host roots to germinate and therefore initiate its infectious lifecycle. Some sorghum varieties have evolved to not produce effective germination stimulants, making them resistant to the parasite. Here, the genetic factors that underpin Striga germination were assessed, followed by a discussion of how such knowledge can be used to develop new Striga management strategies through the disruption of host–parasite communication exchange.Summary Seeds of the parasitic plant Striga are dormant. They only germinate in response to biomolecules emitted from the host's root exudate, strigolactones (SL). But it is now emerging that Striga germination is a much more complex process regulated by crosstalk of hormone signaling pathways. To further understand the genetic basis of the communication exchange between Striga and its host sorghum, we performed a comparative transcriptomic analysis. We sought to identify major transcriptomic changes that define the germination process in Striga and a set of genes that may contribute to the differences in germination rates. Results showed that germination proceeds immediately after SL perception and is marked by a wave of transcriptional reprogramming to allow for metabolic processes of energy mobilization. Cluster analysis using self‐organizing maps revealed a time‐phased and genotype‐differentiated response to germination stimulation. The variation in germination was also a function of hormonal crosstalk. The early germination stage was associated with significant repression of genes in the abscisic acid (ABA) biosynthesis pathway. Other hormones influenced germination as follows: (i) ABA and auxin repressed germination; (ii) brassinosteroid, ethylene, and jasmonic acid promoted germination; and (iii) cytokinin had a more prominent role post‐germination rather than during germination. Perception of SL sets the germination program leading to different rates of germination in sorghum, followed by a complex hormonal regulation network that acts to either repress or enhance germination. We discuss the implications of these findings and present new plausible Striga management strategies.

Seed morphology, germination, and seedling vigor characteristics of fine fescue taxa and other cool‐season turfgrass species

AbstractFine fescue taxa differ in their field establishment rate but it is unclear if this is due to differences in germination rate or seedling growth rate. Research at Purdue University quantified differences in seed morphology, germination vigor, and seedling vigor among 30 cultivars of fine fescue (FF) taxa (Festuca spp.). Strong creeping red fescue (STCRF) (Festuca rubra ssp. rubra), slender creeping red fescue (SLCRF) (F. rubra ssp. littoralis), Chewings fescue (F. rubra ssp. commutata), hard fescue (Festuca brevipila), and sheep fescue (Festuca ovina) were compared with tall fescue (Schedonorus arundinaceus), Kentucky bluegrasses (Poa pratensis), and, perennial ryegrass (Lolium perenne). Seed morphological characteristics differed among FF cultivars and species; however, there was no strong relationship between morphological characteristics and germination vigor. Estimated number of days until 50% germination and mean germination time among the 30 FF cultivars varied, with sheep fescue and Chewings fescue consistently having the slowest germinating cultivars and STCRF cultivars generally the fastest. Species with the fastest to slowest germination ranked as follows: perennial ryegrass &gt; STCRF ≥ SLCRF ≥ hard fescue ≥ Chewings fescue ≥ sheep fescue ≥ tall fescue &gt; Kentucky bluegrass. Seedling vigor measurements among FF indicated the three F. rubra ssp. (STCRF, SLCRF, and Chewings fescue) exhibited faster seedling vigor and greater shoot mass than hard fescue or sheep fescue. Results indicate that past observations of reduced field establishment rates of hard fescue and sheep fescue is primarily due to their slow seedling growth and not reduced germination speed.

Comparison of the Germination Conditions of Two Large-Spore Microsporidia Using Potassium and Sodium Ion Solutions.

The germination of a microsporidian polar tube generally occurs under alkaline conditions. Typically, microsporidian spores can be stored in physiological salt solution for short periods. However, because of differences in the lodging area, the requirements may not always be uniform. In fact, Trachipleistophora sp. OSL-2012-10 (nomen nudum Trachipleistophora haruka) germinated when preserved in physiological salt solution. In this study, the germination characteristics of the large-spore microsporidia Trachipleistophora sp. FOA-2014-10 and Vavraia sp. YGSL-2015-13 were compared with those of Trachipleistophora sp. OSL-2012-10; moreover, we investigated whether these characteristics are specific to these microsporidia. We found that both microsporidia germinated in physiological salt solution. These differences in germination rates were affected by the preservation solution and temperature.

Study on pecan seed germination influenced by seed endocarp.

Nondeep physiological dormancy exists in freshly harvested pecan (Carya illinoinensis) seed, and the endocarp inhibits the seed germination. New methods were tried to detect if “chemical dormancy” or “mechanical dormancy” was caused by the endocarp. The germination of freshly harvested pecan seed with the removal of different parts of the endocarp and the fracture pressure of the endocarp of pecan seed soaked in water at different temperatures were tested. The results showed that (1) there was no significant difference in germination rate between the pecan kernel keeping in touch and out of touch with the same part of the endocarp, (2) whether a part of endocarp was removed to expose the radicle, preventing endocarp from splitting by glue inhibited the radicle elongation significantly, (3) the fracture pressure of the endocarp decreased significantly over water uptake time, and (4) little difference in the fracture pressure of the endocarp between different soaking temperatures. In conclusion, it suggested that (1) the endocarp caused “mechanical dormancy” but “chemical dormancy,” (2) the prevention of radicle elongation was due to the endocarp pressuring the cotyledon rather than the direct physical restriction on the radicle, and (3) the radicle elongation seemed to be able to respond to the suture split and the pressure on the cotyledon.

Germination and Growth Characteristics of Quercus myrsinifolia Blume Seedlings According to Seed Coat Removal, Type of Potting Soil and Irrigation Cycle

The importance of evergreen oak species is increasing due to changes in the ecosystem caused by climate change and environmental changes such as fine dust and carbon dioxide. The Quercus myrsinifolia Blume seeds showed a recalcitrant seed property, where the germination rate decreased when the moisture content was decreased. For seedling propagation of evergreen oak, the effect of oak seed coat (pericarp and testa) removal on germination and seedling growth as well as the effect of potting soil and irrigation cycle on seedling quality were investigated. The germination rate and germination characteristics of Q. myrsinifolia evergreen oak seeds showed significant differences depending on the storage period and the presence or absence of seed coat. Seed coat removal significantly increased germination rate compared to intact seeds, accelerated mean germination time, and increased germination rate and germination value. There was no significant difference in germination rate according to the storage period. The growth of Q. myrsinifolia seedlings was much better in the seeds with the seed coat removed than the intact seeds. The root collar diameter of seedlings germinated from intact seeds was 2.44 mm, and the root collar diameter of seedlings from which the seed coat was removed was 3.38 mm. As a result of the growth characteristics according to the potting soil, 1- and 3-year-old Q. myrsinifolia seedlings showed excellent root growth in commercial potting soil and sand mixed potting soil. Consequently, seedling quality index was 0.124–0.257 according to irrigation and 0.149–0.262 according to potting soil. From observing the root growth of the seedlings according to the irrigation treatment, in the case of 3-year-old seedlings, the total root length was 432 cm when irrigated every 3 days, and the growth was the best. The above results are expected to contribute significantly to the mass propagation of Q. myrsinifolia, which is important for warming and urban greening.

Hermetic bags maintain soybean seed quality under high relative humidity environments

Soybean seed quality is affected by high relative humidity (r.h.) during storage in the humid tropics resulting in loss of germination. This study assessed the effectiveness of hermetic bags in preserving soybean seed quality when stored at high r.h. over three months. Treatments consisted of Purdue Improved Crop Storage (PICS) and control polypropylene (PP) woven bags kept at 30 and 80% r.h. Moisture content and germination were measured each month. Moisture content did not change, except in seed stored in PP bag at 80% r.h. where it more than doubled after one month. There was no significant difference in germination rates between soybean seed stored in PICS bags at 30 and 80% r.h. over three months. Soybean seed stored in PP bag at 30% r.h. had germination rates similar to those observed in PICS bags at 30 and 80% r.h., except after the third month where it significantly decreased compared to PICS bags at 30%. Germination rates of soybean seed stored in PICS at 30% and 80%, and PP bags at 30% decreased by about 3, 6, and 7%, respectively. However, the germination rates of soybean seed stored in PP bags at 80% r.h. dropped by 98% after three months. There was a significant negative correlation of −80.6% (Pearson correlation) between moisture content and seed germination. Farmers and seed producers/traders in the humid tropics can safely preserve soybean seed using commercially available hermetic bags.

Effect of Plant Growth Regulators in In Vitro Culture of Hippophae rhamnoides

This study was carried out to establish in vitro propagation system influenced by plant growth regulators through organogenesis with three different seed sources (China, Mongolia and Russia) for conservation of genetic resources in Northeast Asia. The experiment compared two different carbon sources (commercial sugar, sucrose), which showed no significant differences in germination rate. Induced adventitious buds from leaf segments were found to be highly effective when supplemented with 1.0 mg/L BA, 1.0 mg/L Kinetin, and 5.0 mg/L IAA, in the case of Chinese origin 96.8%, Russian origin R-1: 95.6%, R-2: 85.6%, and Mongolian origin M-2: 77.8%. It was effective in BA and Kinetin with supplemented with IAA, respectively. Shooting development was also efficient in Woody Plant Media (WPM) supplemented with 1.0 mg/L BA, 1.0 mg/L Kinetin and 5.0 mg/L IAA.

Influence of scarification method on seed germination of the terrestrial orchid Anacamptis laxiflora (Lam.)

Abstract A critical step during in vitro sexual propagation of terrestrial orchids is the treatment of the microscopic seeds with a disinfecting solution that kills bacteria and fungi attached to the seeds. This treatment is necessary to prevent infection of the culture vessels. At the same time, the treatment serves to scarify the seeds, a process that disrupts seed dormancy and initiates germination. The literature is inconclusive with respect to the proper combination of disinfecting solution strength and treatment duration. Both factors should be adapted to each species to guarantee minimal infection rate without damaging the embryo. This research aims to compare three disinfection/scarification methods for seeds of Anacamptis laxiflora (Lam.): (i) soaking in 0.5% NaClO, (ii) soaking in 0.5% NaClO, then centrifugation, and (iii) presoaking the seeds in sucrose solution, then soaking in 0.5% NaClO. The seeds were soaked in the disinfecting solution for 5 to 85 min. Following scarification, the seeds were sown in modified Malmgren nutrient medium. Infected and germinated vessels were counted at 41 and 189 d after sowing. We found that the longer the chemical treatment, the lower the infection rate, and the higher the germination rate. There was no significant difference in germination rate between the NaClO and the NaClO-plus-centrifugation method; in fact, the slight savings in disinfection time effected by centrifugation were more than offset by the added complexity of the method. Moreover, we found that centrifugation significantly delays germination. The sucrose presoak-plus-NaClO method was superior to plain NaClO, as the sucrose stimulates the germination of microbial spores on the surface of the seeds, making them easier to kill. Perhaps seeds with thicker testa as well as whole immature capsules could benefit even more from the pretreatment in sucrose solution.

Multi Traits of Phosphate Solublizing Bacterial and Fungal Isolates and Evaluation of Their Potential as Biofertilizer Agent for Coffee Production

Exploitation of phosphate solubilizing bacteria (PSB) and fungi as bioinoculants instead of chemical fertilizers is known to promote plant growth through the supply of plant nutrients. In view of this, the present investigation was planned to assess the phytobeneficial traits of phosphate solublizing bacterial and fungal isolates recovered from coffee arabica rhizosphere/ vermicompost and to determine their potential in growth promotion of coffee seedlings. They were isolated and purified following standard methods. A total number of 154 bacteria and 72 fungi were isolated from vermicompost and coffee rhizosphere. Out of these, twelve potent bacterial and nine fungal isolates were selected and investigated. Among twelve bacterial isolates, three of them showed significant potential to solubilize Ca3 (PO4)2 and had phytobeneficial traits, viz, indole acetic acid, NH3, HCN production and N-fixing ability. The three bacterial isolates (RCHVCB1, RScB1.19 and RMaB2.11) exhibited also remarkable tolerance to ecophysiological factors such as heavy metal, acidity and salinity. These potent isolates were selected for further identification based on morphological and biochemical characteristics and presumptively identified as genera of Pseudomonas (RCHVCB1) and Bacillus (RScB1.19 and RMaB2.11). Similarly, three fungal isolates with superior phosphate solubilizeation ability were characterized and identified as genera Penicillium (RSCF1.19) and Aspergillus (RCHVCF2 and RLVCF2). Consequently, these three efficient bacterial and fungal isolates were evaluated on the coffee seed germination on Petri dish based trial under laboratory condition. The results of inoculated seeds showed significant (p≤0.05) differences in germination rate and vigor index compared to the control. Among all inoculums RScB1.19, RMaB2.11+RSCF1.19 and RMaB2.11 + RLVCF2 showed significantly (p≤0.05) high germination rate (20.59%) over the control (13.33%). Moreover, a single inoculation of RLVCF2, RSCF1.19 and co-inoculation of RMaB2.11 with RLVCF2 also showed significant (p≤0.05) mean root length (1.31cm) and mean shoot length (1.48cm) over the control. These effective bacterial and fungal solublizers can be recommended under field condition as biofertilizer agent and reducing the cost required for chemical fertilizers and providing a step forward towards sustainable agriculture.

Reproductive Output, Synchrony across Depth and Influence of Source Depth in the Development of Early Life stages of Kelp.

Ecklonia radiata is the main foundation species in Australian temperate reefs, yet little has been published on its reproduction and how this may change across its depth range (1-50+m). In this study, we examined differences in sporophyte morphology and zoospore production during a reproductive season and across four depths (7, 15, 25, and 40m). Additionally, we examined differences in germination rate, survival, and morphological traits of gametophytes obtained from these four depths, cultured under the same light and temperature conditions. Multivariate morphology of sporophytes differed significantly between deep (~40m) and shallow sites (7 and 15m), but individual morphological traits were not significantly different across depths. Total spore production was similar across depths but the peak of zoospore release was observed in February at 15m of depth (6,154zoospores · mm-2 of tissue) and the minimum observed in January at 7, 25, and 40m (1,141, 987, and 214zoospores · mm-2 of tissue, respectively). The source depth of zoospores did not have an influence in the germination rate or the survival of gametophytes, and only gametophytes sourced from 40m sites presented significantly less surface area and number of branches. Overall, these results indicate that E. radiata's reproductive performance does not change across its depth range and that kelp beds reproducing in deeper areas may contribute to the replenishment of their shallow counterparts. We propose that deep kelps may constitute a mechanism of resilience against climate change and anthropogenic disturbances.

Electrically Charged Disinfectant Containing Calcium Hydrogen Carbonate Mesoscopic Crystals as a Potential Measure to Control Xanthomonas campestris pv. campestris on Cabbage Seeds.

Xanthomonas campestris pv. campestris (Xcc) is an important seed-borne bacterial pathogen that causes black rot in brassica. Current seed disinfection methods for Xcc have disadvantages; chemical treatment has associated environmental risks, hot water immersion reduces germination, and dry heat treatment is protracted. Here, we treated Xcc-contaminated seeds with CAC-717, a recently developed disinfectant produced by applying an electric field and water flow to distilled water containing calcium hydrogen carbonate to produce mesoscopic crystals. The decimal reduction time (D-value) of Xcc suspension (8.22 log10 colony forming units (CFU)/mL) by CAC-717 treatment was 0.319 min. Treatment of Xcc-contaminated cabbage seeds at 25 °C for 30 min with CAC-717 significantly reduced bacterial cell numbers recovered from the seeds (0.36 log10 CFU/mL (SEM (standard error of the mean) = 0.23 log10 CFU/mL)) compared with distilled water treatment (3.52 log10 CFU/mL (SEM = 0.12 log10 CFU/mL)). Moreover, there was a lower incidence of black rot after treatment with CAC-717 (26.67% ± 3.33%) versus distilled water (56.67% ± 8.82%). For non-contaminated seeds, there was no significant difference in germination rate and plant stem length between distilled water and CAC-717 treatment after 5 days of cultivation. In conclusion, CAC-717 is a promising seed disinfectant without deleterious effects on germination or plant growth.

DoRWA3 from Dendrobium officinale Plays an Essential Role in Acetylation of Polysaccharides.

The acetylation or deacetylation of polysaccharides can influence their physical properties and biological activities. One main constituent of the edible medicinal orchid, Dendrobium officinale, is water-soluble polysaccharides (WSPs) with substituted O-acetyl groups. Both O-acetyl groups and WSPs show a similar trend in different organs, but the genes coding for enzymes that transfer acetyl groups to WSPs have not been identified. In this study, we report that REDUCED WALL ACETYLATION (RWA) proteins may act as acetyltransferases. Three DoRWA genes were identified, cloned, and sequenced. They were sensitive to abscisic acid (ABA), but there were no differences in germination rate and root length between wild type and 35S::DoRWA3 transgenic lines under ABA stress. Three DoRWA proteins were localized in the endoplasmic reticulum. DoRWA3 had relatively stronger transcript levels in organs where acetyl groups accumulated than DoRWA1 and DoRWA2, was co-expressed with polysaccharides synthetic genes, so it was considered as a candidate acetyltransferase gene. The level of acetylation of polysaccharides increased significantly in the seeds, leaves and stems of three 35S::DoRWA3 transgenic lines compared to wild type plants. These results indicate that DoRWA3 can transfer acetyl groups to polysaccharides and is a candidate protein to improve the biological activity of other edible and medicinal plants.

Microplastics accumulate on pores in seed capsule and delay germination and root growth of the terrestrial vascular plant Lepidium sativum

The impacts of nano- and microplastics (<100 nm and <5 mm, respectively) on terrestrial systems is to the present largely unexplored. Plastic particles are likely to accumulate in these systems primarily by the application of sewage sludge. The aim of the current study was to investigate the effects of three sizes of plastic particles (50, 500, and 4800 nm) on a terrestrial plant (cress; Lepidium sativum), using a standardized 72 h bioassay. Cress seeds were exposed to five different concentrations of plastics, ranging from 103 to 107 particles mL−1. Germination rate was significantly reduced after 8 h of exposure for all three sizes of plastics, with increased adverse effect with increasing plastic sizes. Seeds exposed to 4800 nm microplastics showed a germination rate decline from 78% in control to 17% in the highest exposure. No difference in germination rate occurred after 24 h of exposure, regardless of the size of the plastic used. Significant differences in root growth were observed after 24 h, but not after 48 or 72 h of exposure. Impacts on germination are likely due to physical blockage of the pores in the seed capsule by microplastics as shown by confocal microscopy of fluorescent microplastics. In later stages, the microplastics particularly accumulated on the root hairs. This is the first detailed study on the effect of nano- and microplastics on a vascular, terrestrial plant, and our results indicate short-term and transient adverse effects.

Differential sensitivity among Puccinia striiformis f. sp. tritici isolates to propiconazole and pyraclostrobin fungicides

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a destructive disease of wheat in the USA and fungicides have been used to manage the disease. However, it is not clear whether Pst has developed resistance to the commonly used fungicides. In this study, historical and recent Pst isolates were tested for sensitivity to Tilt, a propiconazole demethylation inhibitor fungicide, and Headline, a pyraclostrobin quinone outside inhibitor fungicide. Both Tilt and Headline at their labelled full concentration completely prevented urediniospore germination of all tested isolates. However, differences in germination rate among Pst isolates were observed at reduced fungicide concentrations. In the infection tests of both seedlings and adult plants, the full labelled concentration of either fungicide applied at the same day as inoculation with Pst completely prevented sporulation, but differences in rust sporulation or disease severity were observed among isolates at some reduced fungicide concentrations, or at the same full concentration applied either one day before or 3 or 7 days after inoculation. Thus, the fungicides are still effective for managing stripe rust at the full concentrations, but differences in sensitivity exist among Pst isolates. The results provide the technique and baseline for continually monitoring Pst populations for changes in fungicide sensitivity.

Seed germination of Carex lainzii Luceño, E. Rico &amp; T. Romero: An endemic Spanish endangered species

Abstract. Ribeiro KAF, Madeira de Medeiros C, Agudo JAS, Sánchez JS. 2019. Seed germination of Carex lainzii Luceño, E. Rico &amp; T. Romero: An endemic Spanish endangered species. Biodiversitas 20: xxxx. Strategies to halt the decline of biodiversity include: in-situ and ex-situ conservation, the latter already considered at the global level essential in conservation programs. The results of the germinative responses of Carex lainzii Luceño, E. Rico &amp; T. Romero (Cyperaceae), an endemic Spanish endangered species, are presented in this work, to different trials carried out in the laboratory with seeds harvested in the two known populations of that community. Treatments with and without 0.2% potassium nitrate (KNO3) were tested for four, six and eight months in cold stratification at 5 °C in two germination chambers at different temperatures (22/10 °C and 27/15 °C with a photoperiod of 12/12 hours). The results indicate that there is a large difference in germination rates between the two populations. The use of KNO3 did not increase germination rates in any case, but differences were found between periods of cold stratification, with six months being the most effective. On the other hand, the germination rates of both populations remain low (17.58% and 2%) compared to the obtained rate of seed viability. With this first approach to the understanding of the germination requirements of C. lainzii, it becomes clear that new essays are needed to obtain better results, in order to effectively implement the protection plans of C. lainzii populations.