Reduced Seedling Growth Research Articles

Određivanje optimalnih doza gama zračenja kod indukovanih mutacija pšenice i ječma

One of the major challenges that plant breeders face in the 21st century is food safety for growing human population coupled with extreme climate changes. Accordingly, the most important breeders' goal is to find appropriate methods in response to these challenges in order to create high-yielding varieties resilient to abiotic and biotic stressors. The aim of this study was to determine optimal doses of gamma irradiation in two wheat and one barley varieties and to apply the identified doses for development of mutant populations. Wheat and barley varieties showed different reactions to applied doses of gamma irradiation. Wheat varieties had germination rate over 90% at all applied doses while barley seeds showed to be more susceptible to gamma irradiation. Gamma irradiation had greater influence on seedling height which was clearly demonstrated by growth reduction with increasing radiation doses. ANOVA showed a significant difference between genotypes, applied doses of gamma radiation as well as genotype by doses interaction for seedling height. At highest dose of 600 Gy, the reduction of seedling height was 94.6%, 96.5% and 96.8% in Simonida, Rudnik and NS 40S, respectively. The irradiation doses that resulted in seedling growth reduction by 50% (GR50) were 210 Gy for barley Rudnik and wheat NS 40S, and 310 Gy for wheat variety Simonida. Identified doses were used for the irradiation of 2000 seeds of each variety in order to produce mutant populations that will be further used in a breeding program for development of varieties with increased resilience to climate change.

ZmDRR206 functions in maintaining cell wall integrity during maize seedling growth and defense response to external stresses

Plants adaptively change their cell wall composition and structure during their growth, development, and interactions with environmental stresses. Dirigent proteins (DIRs) contribute to environmental adaptations by dynamically reorganizing the cell wall and/or by generating defense compounds. A maize DIR, ZmDRR206, was previously reported to play a dominant role in regulation of storage nutrient accumulation in endosperm during maize kernel development. Here we show that ZmDRR206 mediates maize seedling growth and disease resistance by coordinately regulating biosynthesis of cell wall components for cell-wall integrity (CWI) maintenance. Expression of ZmDRR206 was induced in maize seedlings upon pathogen infection. ZmDRR206 overexpression in maize resulted in reduced seedling growth and photosynthetic activity but increased disease resistance and drought tolerance, revealing a tradeoff between growth and defense. Consistently, ZmDRR206 overexpression reduced the contents of primary metabolites and down-regulated genes involved in photosynthesis, while increasing the contents of major cell wall components, defense phytohormones, and defense metabolites, and up-regulated genes involved in defense and cell-wall biosynthesis in seedlings. ZmDRR206-overexpressing seedlings were resistant to cell-wall stress imposed by isoxaben, and ZmDRR206 physically interacted with ZmCesA10, which is a cellulose synthase unit. Our findings suggest a mechanism by which ZmDRR206 coordinately regulates biosynthesis of cell-wall components for CWI maintenance during maize seedling growth, and might be exploited for breeding strong disease resistance in maize.

Bioherbicide potential of essential oils from plant species used in folk medicine and cuisine in the Amazon region

The potential of essential oils (EOs) has been proven for several solutions in the agricultural sector, among others, which makes the exploration of this matrix an ongoing activity. From this perspective, this work investigated essential oils from medicinal and condimentary species commonly used in the Amazon region for the control of Eragrostis plana Nees, an invasive species with a great impact on forage production. The EOs of Copaifera sp., Bixa orellana L., Piper tuberculatum Jacq., Chenopodium ambrosioides L. and Ocimum gratissimum L. were obtained via hydrodistillation, characterized via GC–MS and used in the preparation of solutions that were applied in vitro tests E. plana. All EOs tested affected the germination and initial growth of E. plana, but that of C. ambrosioides was the most efficient in inhibiting emergence, reaching a reduction greater than 97 % in accumulated germination when applied at a concentration of 0.1 %, followed by the EO of O. gratissimum, with inhibition of almost 75 % at the same concentration. The other oils, although in higher concentrations, also showed an interesting potential for controlling the germination of this invasive species. Similarly, a significant and more pronounced reduction in the initial growth of seedlings was observed in exposure to the EO of C. ambrosioides, which showed a major volatile composition characterized by the identification of ascaridol (5.75 %), glycosylated ascaridol (10.58 %), linalool acetate (11.26 %) and dihydrocitronellol acetate (19.53 %). These results, although initial, validate the efficiency of essential oils as promising biological products for application in the agricultural sector.

Pyrimidine catabolism is required to prevent the accumulation of 5-methyluridine in RNA.

5-Methylated cytosine is a frequent modification in eukaryotic RNA and DNA influencing mRNA stability and gene expression. Here we show that free 5-methylcytidine (5mC) and 5-methyl-2'-deoxycytidine are generated from nucleic acid turnover in Arabidopsis thaliana, and elucidate how these cytidines are degraded, which is unclear in eukaryotes. First CYTIDINE DEAMINASE produces 5-methyluridine (5mU) and thymidine which are subsequently hydrolyzed by NUCLEOSIDE HYDROLASE 1 (NSH1) to thymine and ribose or deoxyribose. Interestingly, far more thymine is generated from RNA than from DNA turnover, and most 5mU is directly released from RNA without a 5mC intermediate, since 5-methylated uridine (m5U) is an abundant RNA modification (m5U/U ∼1%) in Arabidopsis. We show that m5U is introduced mainly by tRNA-SPECIFIC METHYLTRANSFERASE 2A and 2B. Genetic disruption of 5mU degradation in the NSH1 mutant causes m5U to occur in mRNA and results in reduced seedling growth, which is aggravated by external 5mU supplementation, also leading to more m5U in all RNA species. Given the similarities between pyrimidine catabolism in plants, mammals and other eukaryotes, we hypothesize that the removal of 5mU is an important function of pyrimidine degradation in many organisms, which in plants serves to protect RNA from stochastic m5U modification.

Morphological, Biochemical and Genetic Variation of Rice (Oryza sativa L.) Genotypes to Vegetative Stage Salinity Stress

Salinity is one of the most serious issues in rice cultivation and production. Salt stress significantly reduced seedling growth performance of rice. This research was conducted to study the effects of vegetative stage salinity stress on morphological, biochemical, molecular and genetic variation of 12 rice genotypes as well as 2 check varieties, MR297 (susceptible) and Pokkali (tolerant). The experiment was arranged in a split-plot design with 3 replications. Normal freshwater at 0 dS m-1 (L1), saline water at 6 dS m-1 (L2) and saline water at 12 dS m-1 (L3) were the main plot and rice genotypes were the sub-plot. In general, morphological and biochemical traits of all genotypes showed an overall reduction of about 47.41% in L3 as compared to L1 except for the tolerant check, Pokkali. The genetics and correlation analysis indicated that plant height, leaf size and standard evaluation system (SES) score might be used as a selection criterion in developing salt tolerant rice. The multivariate analysis revealed that a Malaysian landraces, Jarom Mas was clustered together with Pokkali as tolerant genotype. Screening using tightly linked Simple Sequence Repeat (SSR) markers (RM1287, RM10748, RM493) of salinity tolerant QTL, Saltol indicated that this QTL was absence in Jarom Mas. This finding might indicate the presence of other QTL associated with salinity tolerance in Jarom Mas. Further study on identifying the speculated QTL may be conducted to confirm this postulation.

Fatty acid amide hydrolase and 9-lipoxygenase modulate cotton seedling growth by ethanolamide oxylipin levels.

Polyunsaturated N-acylethanolamines (NAEs) can be hydrolyzed by fatty acid amide hydrolase (FAAH) or oxidized by lipoxygenase (LOX). In Arabidopsis (Arabidopsis thaliana), the 9-LOX product of linoleoylethanolamide, namely, 9-hydroxy linoleoylethanolamide (9-NAE-HOD), is reported to negatively regulate seedling development during secondary dormancy. In upland cotton (Gossypium hirsutum L.), six putative FAAH genes (from two diverged groups) and six potential 9-LOX genes are present; however, their involvement in 9-NAE-HOD metabolism and its regulation of seedling development remain unexplored. Here, we report that in cotton plants, two specific FAAH isoforms (GhFAAH Ib and GhFAAH IIb) are needed for hydrolysis of certain endogenous NAEs. Virus-induced gene silencing (VIGS) of either or both FAAHs led to reduced seedling growth and this coincided with reduced amidohydrolase activities and elevated quantities of endogenous 9-NAE-HOD. Transcripts of GhLOX21 were consistently elevated in FAAH-silenced tissues, and co-silencing of GhLOX21 and GhFAAH (Ib and/or IIb) led to reversal of seedling growth to normal levels (comparable with no silencing). This was concomitant with reductions in the levels of 9-NAE-HOD, but not of 13-NAE-HOD. Pharmacological experiments corroborated the genetic and biochemical evidence, demonstrating that direct application of 9-NAE-HOD, but not 13-NAE-HOD or their corresponding free fatty acid oxylipins, inhibited the growth of cotton seedlings. Additionally, VIGS of GhLOX21 in cotton lines overexpressing AtFAAH exhibited enhanced growth and no detectable 9-NAE-HOD. Altogether, we conclude that the growth of cotton seedlings involves fine-tuning of 9-NAE-HOD levels via FAAH-mediated hydrolysis and LOX-mediated production, expanding the mechanistic understanding of plant growth modulation by NAE oxylipins to a perennial crop species.

Effect of Exogenous Treatment with Nitric Oxide (NO) on Redox Homeostasis in Barley Seedlings (Hordeum vulgare L.) Under Copper Stress

The protective mechanism of nitric oxide (NO) in regulating tolerance to Cu-induced toxicity in shoots of barley (Hordeum vulgare L.) was studied. The experiment consisted of four treatments based on additions to basal nutrient solutions (BNS): control (CTR), Cu (200 µM), SNP (500 µM), and Cu (200 µM) + SNP (500 µM) over a period of 10 days. Treatment with Cu significantly reduced seedling growth and photosynthetic efficiency concomitant with an increase in reactive oxygen species contents, lipid peroxidation markers, and antioxidant enzyme activities, indicating that Cu induced oxidative stress. Furthermore, growth inhibition of Cu-treated plants was associated with a reduction in photosynthetic pigments and maximum photosystem II efficiency as well as a strong decrease in levels of glutathione (GSH) and ascorbate (AsA). Addition of a nitric oxide (NO) donor, sodium nitroprusside (SNP), to the growth medium alleviated Cu toxicity by decreasing Cu uptake and enhancing antioxidant capacity, as indicated by increased contents of GSH and AsA. The application of SNP decreased oxidative stress and lipid peroxidation by suppressing lipoxygenase activity and enhancing some antioxidant enzyme activities. The results obtained indicate the potential of exogenously applied SNP in the management of metal toxicity. Hence, NO generating compounds have potential agronomical applications when cultivating in contaminated areas. Our findings indicate that NO can alleviate Cu toxicity by affecting the antioxidant defense system and maintaining the glutathione-ascorbate cycle status, suggesting that SNP treatment protects proteins against oxidation by regulating the cellular redox homeostasis.

Physiological and Biochemical Mechanisms of Exogenous Calcium Chloride on Alleviating Salt Stress in Two Tartary Buckwheat (Fagopyrum tataricum) Varieties Differing in Salinity Tolerance

Salt stress is one of the most serious abiotic stresses limiting plant growth and development. Calcium as an essential nutrient element and important signaling molecule plays an important role in ameliorating the adverse effect of salinity on plants. This study aimed to investigate the impact of exogenous calcium on improving salt tolerance in Tartary buckwheat cultivars, cv. Xinong9920 (salt-tolerant) and cv. Xinong9909 (salt-sensitive). Four-week-old Tartary buckwheat seedlings under 100 mM NaCl stress were treated with and without exogenous calcium chloride (CaCl₂), Ca²⁺ chelator ethylene glycol tetraacetic acid (EGTA) and Ca²⁺-channel blocker lanthanum chloride (LaCl₃) for 10 days. Then, some important physiological and biochemical indexes were determined. The results showed that salt stress significantly reduced seedling growth, decreased photosynthetic pigments, inhibited antioxidants and antioxidant enzyme activities. However, it increased the reactive oxygen species (ROS) levels in the two Tartary buckwheat cultivars. Exogenous 10 mM CaCl₂ application on salt-stressed Tartary buckwheat seedlings obviously mitigated the negative effects of NaCl stress and partially restored seedlings growth. Ca²⁺-treated salt-stressed seedlings diplayed a suppressed accumulation of ROS, increased the contents of total chlorophyll, soluble protein, proline and antioxidants, and elevated the activities of antioxidant enzymes compared with salt stress alone. On the contrary, the addition of 0.5 mM LaCl₃ and 5 mM EGTA on salt-stressed Tartary buckwheat seedlings exhibited the opposite effects to those with CaCl₂ treatment. These results indicate that exogenous Ca²⁺ can enhance salt stress tolerance and Ca²⁺ supplementation may be an effective practice to cultivate Tartary buckwheat in saline soils.

Stimulating effects of cold plasma seed priming on germination and seedling growth of cumin plant

Improving germination and seedling establishment can effectively increase crop yields. Cold plasma (CP) seed priming can be used as an emerging tool to improve germination efficiency and increase seedling growth. The effects of CP seed priming for different time periods (5 and 10 min) on germination, seedling growth, seedling root morphology, photosynthetic pigments, antioxidant defense system and nutrient uptake of Cuminum cyminum L. (cumin) were investigated. Seed priming with 5 and 10 min CP improved the germination efficiency and germination index by increasing the water absorption capacity of the seeds. CP seed priming for 5 min induced growth, biomass production, proline content and antioxidant defense system of cumin seedlings. Seed pretreatment with 5 min CP enhanced nutrient uptake by increasing root growth, volume and area surface and, consequently, improved photosynthetic pigment contents and growth of cumin seedling. However, 10 CP pretreatment induced oxidative stress and damage to membrane lipids by excessively increasing the level of active species (H2O2 and superoxide anion), resulting in reduced seedling growth and biomass compared to control ones. Therefore, seed priming with CP at the appropriate time duration can be a promising tool to increase germination efficiency and improve seedling establishment in aromatic and medicinal plants.

Allelopathic Effect of Serphidium kaschgaricum (Krasch.) Poljak. Volatiles on Selected Species.

The chemical profile and allelopathic effect of the volatile organic compounds (VOCs) produced by a dominant shrub Serphidium kaschgaricum (Krasch.) Poljak. growing in northwestern China was investigated for the first time. Serphidium kaschgaricu was found to release volatile compounds into the surroundings to affect other plants’ growth, with its VOCs suppressing root elongation of Amaranthus retroflexus L. and Poa annua L. by 65.47% and 60.37% at 10 g/1.5 L treatment, respectively. Meanwhile, volatile oils produced by stems, leaves, flowers and flowering shoots exhibited phytotoxic activity against A. retroflexus and P. annua. At 0.5 mg/mL, stem, leaf and flower oils significantly reduced seedling growth of the receiver plants, and 1.5 mg/mL oils nearly completely prohibited seed germination of both species. GC/MS analysis revealed that among the total 37 identified compounds in the oils, 19 of them were common, with eucalyptol (43.00%, 36.66%, 19.52%, and 38.68% in stem, leaf, flower and flowering shoot oils, respectively) and camphor (21.55%, 24.91%, 21.64%, and 23.35%, respectively) consistently being the dominant constituents in all oils. Eucalyptol, camphor and their mixture exhibited much weaker phytotoxicity compared with the volatile oils, implying that less abundant compounds in the volatile oil might contribute significantly to the oils’ activity. Our results suggested that S. kaschgaricum was capable of synthesizing and releasing allelopathic volatile compounds into the surroundings to affect neighboring plants’ growth, which might improve its competitiveness thus facilitate the establishment of dominance.

Cinnamic Acid Increased the Incidence of Fusarium Wilt by Increasing the Pathogenicity of Fusarium oxysporum and Reducing the Physiological and Biochemical Resistance of Faba Bean, Which Was Alleviated by Intercropping With Wheat.

BackgroundContinuous cropping has resulted in the accumulation of self-toxic substances in faba beans which has restricted their global production. Intercropping is widely used to alleviate these problems.AimsTo explore the role of cinnamic acid stress in faba bean physiology and disease resistance, and the potential mitigating effects of intercropping the faba bean with wheat.MethodsFaba bean seedlings were grown with or without wheat in both field and hydroponic conditions in the presence of different cinnamic acid concentrations and Fusarium oxysporum (FOF), the occurrence of. Fusarium-mediated wilt and oxidative stress, as well as plant growth indices and the anti-pathogen defense system were analyzed.ResultsCinnamic acid significantly increased Fusarium pathogenicity, inhibited the activity of defense enzymes and reduced the ability of plants to resist pathogens, indicating the importance of cinnamic acid in the promotion of Fusarium wilt resulting in reduced seedling growth. Intercropping with wheat improved plant resistance by alleviating cinnamic acid-induced stress, which promoted crop growth and decreased the incidence and disease index of Fusarium wilt.ConclusionCinnamic acid promotes Fusarium wilt by stimulating pathogen enzyme production and destroying the defense capability of faba bean roots. Intercropping reduces Fusarium wilt by alleviating the damage caused by cinnamic acid to the defense system of the faba bean root system.

Radiosensitivity of two varieties of watermelon (Citrullus lanatus) to different doses of gamma irradiation

Watermelon (Citrullus lanatus) is one of the most popular fruits in Cameroon and the world at large. However, the extreme sensitivity of watermelon to parasites and climatic vagaries makes its cultivation demanding of chemical inputs that can have negative impacts on human health and the environment. In Cameroon, there is a slow improvement of fruit yield in watermelon breeding due to the lack of natural heritable genetic variation, which is a prerequisite for genetic improvement of crops. Such variation can be created through either random or targeted processes on genotypes with appropriate doses of radiation. Genetic improvement by induced mutagenesis appears today alongside hybridization as an alternative method of creating new plant varieties. However, the success of this approach is determined by the application of an appropriate and ideal dose of mutagen. The objective of this study was to evaluate the radiosensitivity of the two most cultivated watermelon varieties in Cameroon to gamma radiation from 60Co in order to determine an optimal dose or lethal dose 50 (LD50) for the induction of the genetic variability necessary for genetic improvement. Seeds of the Kaolack and Crimson sweet watermelon varieties were irradiated with five doses of gamma radiation (100, 200, 300, 400 and 600 Gy) in the laboratory of the International Atomic Energy Agency in Seibersdorf, Austria. These seeds were cultivated in a greenhouse following an utterly randomized device with three repetitions, and parameters such as the germination rate, the survival rate and the shoot length of plants were evaluated. High rates of 90% and 75% germination were obtained, respectively, for the control treatments of Kaolack and Crimson sweet, while the lowest rates were 35% at 600 Gy for Kaolack and 30% at 400 Gy for Crimson sweet. The highest survival rate of plants (96.66%) was obtained with the control seeds of the Kaolack. This variety had the lowest survival rate (45.6%) at 600 Gy dose. Statistical analysis of data obtained helped to estimate the ideal LD50 doses based on growth reduction of seedlings’ heights after gamma-ray treatment. Using a linear regression model based on parameters like plant size, the LD50 doses for Kaolack and Crimson sweet were calculated at 225.40 Gy and 221.56 Gy, respectively, and predicted between 200 and 250 Gy. These results show that the two varieties evaluated were radiosensitive as clearly expressed in the parameters evaluated, where the values decreased with the increase in the irradiation dose. The LD50 doses from this study could be safely applied as reference doses for large-scale gamma irradiation of watermelon genotypes to create desirable agronomic traits in the mutation breeding efforts.

The performance of three local rice (Oryza sativa L.) cultivar from East Kalimantan - Indonesia under drought stress at early seedling stage

Climate change made rain fall unpredictable leading to sudden drought stress during crop cultivation period. Drought stress affects the crop growth and development, especially during the seedling period. This research aims to evaluate the performance of three local rice seedling under drought stress induced by PEG 6000. Three local rice cultivars were germinated and then divided into five groups. In the 3 d after germination, each group were treated in vitro with either 0 %, 10 %, 15 %, 20 % or 25 % PEG 6000 solution for 10 d in vitro. Drought stress was continued for 14 d ex vitro in rice treated with 0 % and 25 % PEG. Osmotic stress induced by PEG significantly reduced plant growth and total chlorophyll content in the leaf. In vitro study showed rice seedling growth reduction was increased when the PEG 6000 increased. Ex vitro study with application of 25 % PEG showed cv. Telaseh more tolerant to drough stress at the seedling stage compare to cv.. Mayas Kuning and cv. Mayas Putih. Additionally, drought stress induced increasing of soluble sugar in the leaf of all rice cultivars. This might indicate that soluble sugar plays a role as osmoprotectant under drought stress in those three cultivars.

Photosynthetic pigments and vigour of rice (Oryza sativa L.) seedlings as affected by kinetin and prohexadione-calcium

In the present study effects of exogenous application of Kinetin (Kn @ 10, 20 and 40 mg/l) and Prohexadione calcium (BX-112 @ 5, 10 and 20 mg/l) were studied on rice (Oryza sativa L.) cultivars viz PB-2, PB-3 and PUSA 112. Different levels of Kn and BX-112 were applied to seedlings, five days after sowing (DAS). The content of photosynthetic pigments (total chlorophyll) was recorded at fourteen DAS stage, furthermore application of Kn significantly improved it in selected cultivars with more percent increase at 7 DAS. The content of accessory pigments (carotenoids) was recorded higher in both Kn as well as BX-112 treated sets. Kn application promoted vigour of rice seedlings in the selected cultivars with more pronounced effect in treatments involving higher concentration of Kn. BX-112 decreased both the vigour and relative growth rate (RGR) that led to reduction in growth of seedlings of all the three cultivars. This study revealed that though both Kn and BX-112 improved accumulation of photosynthetic pigments yet Kn application promoted growth and vigour of the seedlingswhile BX-112displayed an inhibitory effect on vigour of rice seedling.

Determination of lethal dose and effect of EMS and gamma ray on germination percentage and seedling parameters in barnyard millet variety Co(Kv)2

An experiment was conducted to estimate the lethal dose of the chemical mutagen EMS and physical mutagen gamma ray in barnyard millet variety Co(Kv) 2. Genetically pure seeds were treated with different doses of EMS viz. 30mM, 40mM, 50mM, 60mM, 70mM, 80mM, 90mM and 100mM and gamma rays viz., 500 Gy, 600 Gy, 700 Gy, 800 Gy, 900Gy and 1000 Gy. The LD50 values were observed based on growth reduction of seedlings after EMS and gamma ray treatment. The LD50 dose for EMS and gamma ray under in vitro and in vivo condition were fixed at 70mM and 800 Gy respectively, based on probit analysis. As the doses of applied EMS and gamma ray increased, there was a decrease in germination, survival rate of seedlings, root length, shoot length, seedling height, vigour index under in vitro conditions and emergence and survival under field (in vivo) conditions in M1 generation as compared to the control.

Species- and developmental stage-specific effects of allelopathy and competition of invasive Impatiens glandulifera on co-occurring plants.

BackgroundImpacts of invasive species on native communities are often difficult to assess, because they depend on a range of factors, such as species identity and traits. Such context-dependencies are poorly understood yet, but knowledge is required to predict the impact of invasions.Materials and methodsWe assessed species- and developmental stage-specificity of competitive and allelopathic effects of the invasive plant Impatiens glandulifera on different developmental stages of four native plant species. While some studies have shown a reduction in plant growth caused by I. glandulifera, the magnitude of its impact is ambiguous. For our study we used seedlings and juveniles of I. glandulifera and the native target species Geum urbanum, Filipendula ulmaria, Urtica dioica, and Salix fragilis (seedlings only of the latter), which often co-occur with I. glandulifera in different habitats. Plants were grown in competition with I. glandulifera or treated with I. glandulifera leaf material, or 2-metoxy-1,4-naphtoquinone (2-MNQ), its supposedly main allelochemical.Results and conclusionsOverall I. glandulifera had a negative effect on the growth of all target species depending on the species and on the plant’s developmental stage. F. ulmaria was the least affected and U. dioica the most, and seedlings were less affected than juveniles. The species-specific response to I. glandulifera may lead to an altered community composition in the field, while growth reduction of seedlings and juveniles should give I. glandulifera an advantage in cases where plant recruitment is crucial. 2-MNQ led to minor reductions in plant growth, suggesting that it may not be the only allelopathic substance of I. glandulifera. Surprisingly, I. glandulifera was not fully tolerant to 2-MNQ. This autotoxicity could contribute to I. glandulifera population dynamics. We conclude that I. glandulifera reduces the growth of native vegetation and alters early successional stages without fully hindering it.

Salinity effect on germination, seedling growth and cotyledon membrane complexes of a Portuguese salt marsh wild beet ecotype

Sugar beet (Beta vulgaris L.) high yields have been achieved through irrigation and this crop is described as coping with mild salinity (40–120 mM NaCl). However, during seed germination, sugar beet is salinity sensitive and soil salinity should not exceed 3 dS/m. Wild beets, ancestors of sugar beet, are naturally able to germinate and grow in saline environments. Salinity tolerance during germination and early seedling development of three Portuguese wild beet ecotypes [Comporta (CMP), Oeiras (OEI), Vaiamonte (VMT)] and one sugar beet cultivar (Isella) was evaluated. Concerning germination, VMT outperformed all the other beets, with 98% (± 2%) of glomerules germinating in 200 mM NaCl after 14 days of scarification. However, in 500 mM NaCl, only CMP was able to initiate and maintain radicle emergence, though in a very small extension (< 3%). On the basis of the relative salinity tolerance index, CMP is the less affected by salinity, despite reduced seedling growth and biomass. Since cotyledons length and membrane proteins abundance were negatively affected by salinity, the hypothesis was raised that membranes functionality, including the photochemical multiprotein complexes, was compromised. To test this hypothesis, a blue-native two-dimensional electrophoresis was applied to CMP seedlings. In the cotyledonary leaves, complexes LC1 and LC4 and several components of LC2, LC5, LC6 complexes were negatively affected by salinity. The components of the complexes of photosystem I and ATP synthase were less abundant what points out to a lower cotyledon capacity for ATP synthesis and ferredoxin reduction. Lower availability of ATP and reduced ferredoxin imply reduced photosynthetic assimilation and, therefore, lower carbon availability for growth.

Decision-making criteria for plant-species selection for phytostabilization: Issues of biodiversity and functionality

In polluted protected areas, using phytoremediation raises the question of the choice of the plant species to select. As an example, Atriplex halimus has been identified as a proliferative plant species that needs to be eradicated in the Calanques National Park (PNCal). Since it has been proven that the spontaneous populations of this plant species could phytostabilize shore waste deposits generated by past industrial activities within the PNCal territory, its status seems controversial, presenting a dilemma between biodiversity management of a protected area and ecological solutions for pollution management. To address this issue, we assessed the ability of A. halimus to grow on different soils from this territory, in order to estimate the potential invasiveness of this plant in this territory. Petri dish germinations and pot-growth experiments showed 50% germination of seeds collected on local individuals from the most polluted PNCal soil and 20% growth reduction of seedlings. Soil analysis showed that limitation of growth was caused by high pH value and sparsely available micronutrients as well as metal and metalloid contamination. Our results suggested that local populations of A. halimus may stabilize the highly metal and metalloid polluted salt-affected soils of the PNCal, with low seed germination potential lowering the eventuality of a propagation over the PNCal territory. As a consequence of this study, the administration of the PNCal decided not to remove A. halimus populations along the polluted coastline until another solution to prevent pollution dispersal had been found. This laboratory approach may be extended to other similar situations where plant species may be evaluated not only in term of phytoremediation potential but also in term of biodiversity preservation.

Comparing salt-induced responses at the transcript level in a salares and coastal-lowlands landrace of quinoa (Chenopodium quinoa Willd)

To further our understanding of the mechanisms governing salt stress responses and adaptation in halophytes, we explored morphological, metabolic, and gene expression responses to high salinity in quinoa (Chenopodium quinoa Willd). The main objective of this study was to analyze selected responsive genes in a time-course experiment to test for expression kinetics and to compare short-term salt-induced effects at the transcript level between two Chilean landraces belonging to different ecotypes. Quinoa genotypes exhibit a large variability in their responses to salinity, but it is not clear whether this is strictly related to the ecotype to which they belong. We tested this hypothesis by comparing the expression levels of genes involved in growth, ion homeostasis, abscisic acid (ABA) biosynthesis, perception, and conjugate cleavage, polyamine (PA) biosynthesis and oxidation, and proline biosynthesis as well as genes encoding ABA-dependent and −independent transcription factors. Landraces R49 (salares ecotype) and Villarrica (VR, coastal-lowlands ecotype) were analyzed from 0.5 to 120h after transfer to saline (300mM NaCl) or non-saline (control) medium. All the genes, except CqSOS1 and CqNHX, were investigated here for the first time in quinoa under salt stress. Transcript levels were determined by quantitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR) analysis. Germination, seedling growth, ABA, and PA contents were evaluated in parallel. Even though on saline medium germination was inhibited in VR but not in R49, seedling growth reduction at 120h was not substantially different in the two landraces. The ABA biosynthetic enzyme NCED was the most strongly salt-induced gene; ABA content was similarly enhanced (shoots) or unaffected (roots) in both R49 and VR. NaCl treatment also altered transcript levels of some PA metabolic enzymes and the PA profile leading to an enhanced ratio between the higher PAs and putrescine. All other genes also exhibited similar expression profiles in response to salinity in the two landraces especially in roots, while in shoots some differences were observed. Our results provide new information indicating that crucial salt adaptation strategies at the molecular level and in terms of ABA and PA contents are shared by the coastal-lowlands and salares landraces; however, the timing of the onset of transcriptional changes (e.g., NCED, ABF3, and RD22) may reflect genotype-dependent constitutive and/or inducible adaptive strategies.

Effects of silicon soil amendments and nitrogen fertilizer on apple snail (Ampullariidae) damage to rice seedlings

This study examines the potential for silicon soil amendments and nitrogen to reduce apple snail, Pomacea canaliculata Lamarck, damage to rice (Oryza sativa L.) seedlings. A rate of 75 kg/ha of nitrogen applied as (NH4)2SO4 to rice (cv IR64 and cv YTH183) seedbeds increased seedling biomass, allowing the seedlings to gain critical stem thickness and avoid snail herbivory. These seedlings remained relatively large after exposure to snails in pot experiments, mainly because of faster growth rates, but also due to lower damage from snails to >21 day-old IR64 seedlings. Silicon applied as Na2O3Si·9H20 alone (without nitrogen) reduced seedling growth compared to control seedlings. When nitrogen and silicon were applied together, the addition of silicon resulted in reduced seedling growth in YTH183 compared to seedlings treated with nitrogen alone. However, the same effect was not noted for IR64 seedlings, indicating clear variety-specific responses to seedbed inputs. Regardless of variety, silicon-treated seedlings that were transplanted to snail-infested pots at 21 days after seeding (DAS) had lower biomass than seedlings without silicon despite silicon-treated IR64 seedlings having less snail damage than untreated controls. From an experiment conducted in snail-infested ponds, we found no difference between snail damage to silicon (SiO2)-treated and control cv IR50 seedlings. Although we did not determine silicon levels in plant tissues, our results indicate that the effects of silicon soil amendments are largely insufficient to reduce the impact of apple snails to young rice seedlings (≤21 DAS).