Shoot Elongation Rate Research Articles

Efficient Plantlet Regeneration from Branches in Mangifera indica L.

Mango (Mangifera indica L.) is one of the most significant tropical and subtropical fruit species, with high ecological and economic value. However, research on the in vitro culture of mangoes is relatively weak, so establishing an efficient and stable mango plant regeneration system is of great significance. In this study, a preliminary mango regeneration system was established with Mangifera indica L. cv. Keitt from young branches as the starting explants. The results showed that the optimal plant growth regulator (PGR) formula for direct adventitious shoot induction on the branches was 1 mg/L 6-benzylaminopurine (6-BA) + 0.1 mg/L a-naphthaleneacetic acid (NAA), with an adventitious shoot induction rate of 73.63% and an average of 6.76 adventitious shoots. The optimal basal medium for adventitious shoot induction was wood plant medium (WPM), with an adventitious shoot induction rate of 63.87% and an average of 5.21 adventitious shoots. The optimal culture medium for adventitious shoot elongation was WPM + 1 mg/L 6-BA + 0.5 mg/L NAA, with an adventitious shoot elongation rate of 89.33% and an average length of 5.17 cm. The optimal formula for the induction of mango rooting was Douglas fir cotyledon revised medium (DCR) + 3 mg/L indole-3-butyric acid (IBA), with a maximum rooting rate of 66.13% and an average rooting quantity of 6.43. The genetic fidelity of the in vitro-regenerated plants was evaluated using inter-simple sequence repeat (ISSR) molecular markers. There was no difference between the in vitro-regenerated plants and the parent plant. This study provides an efficient and stable propagation system for Mangifera indica L., laying the foundation for its rapid propagation and genetic improvement.

Effects of different rootstocks on the growth and yield characteristics of Papazkarası (Vitis vinifera L.)

Rootstocks, which are becoming increasingly important in viticulture, influence the growth, yield, and grape quality of the grafted variety. Therefore, understanding the resistance characteristics of rootstocks to phylloxera, nematodes, environmental conditions, and abiotic and biotic stresses is crucial. Selecting a rootstock that is appropriate for the region where the vineyard will be established optimizes grape quality. The aim of this research is to determine the performance of the cv. Papazkarası on different rootstocks. For this purpose, an experiment was established at Irem Çamlica Viticulture and Winery Co. vineyard in Kırklareli province. Ten-year-old Papazkarası vines grafted onto 1103P, 110R, and 420A rootstocks were used as plant material. To determine the growth of the vines, parameters such as shoot elongation rate (cm/week), shoot length changings (cm), pruning wood weight (PW) (kg/vine), vigor (g), puissance, number of buds per square meter (number), balanced pruning buds number (number/vine), vegetative growth (VG), Ravaz Index (RI), Partridge Index (PI), and yield (kg/vine) were examined. Additionally, to determine cluster characteristics, cluster width and length (cm), weight (g), and the volume of gappy and spaceless clusters (cm³) were measured. The results of the research indicated that the 1103P rootstock had the lowest yield, puissance, RI, PI, and VG values; moderate values for PW, vigor, number of shoots, number of berries per cluster, and cluster length; and the highest values for cluster weight, the volume of gappy and spaceless clusters. The 110R rootstock was found to be more balanced compared to other rootstocks, with the highest values for vigor, RI, and PI; average values for yield, puissance, and VG; and the lowest values for PW, number of shoots, number of berries per cluster, cluster length, weight, and the volume of gappy and spaceless clusters. The 420A rootstock had the highest values for yield, PW, VG, number of shoots, number of berries per cluster, and cluster width and length; average values for RI, PI, cluster weight, and the volume of gappy and spaceless clusters; and the lowest value for one-year-old cane weight. In conclusion, based on the characteristics outlined, a selection can be made from these rootstocks according to cultivation purposes, but other rootstocks should also be investigated.

Dynamic changes in evapotranspiration, canopy photosynthesis and expansive growth in open field under rapid fluctuating radiation

In open fields, plants experience dynamic changes in environment, particularly radiation, temperature, wind, and humidity but their short-term responses have not been adequately characterized under natural conditions. In this study, we assessed causal effects of rapid radiation fluctuation on seven plant parameters in open fields of cotton and sweet corn canopies. The parameters are evapotranspiration (ET), canopy photosynthesis indicated by CO2 flux from air to canopy (FCO2), sensible heat energy flux (H), canopy conductance for water vapor (gcw), canopy surface temperature (Ts), shoot and leaf elongation rate, and stem diameter change. The energy and CO2 fluxes were measured with Bowen ratio/energy balance/CO2 gradient (BREB+) technique, using averaging time of 5 min. Shoot + leaf elongation and stem diameter change were monitored with position transducers using averaging time of 1 min. All parameters were all found to respond to change in radiation and transpiration within minutes or sooner. While radiation effects on canopy gas exchanges are expected, illuminating are the indirect but immediate effects on shoot + leaf growth and stem diameter change through radiation effects on transpiration and plant water status. A novel finding is that gcw also responded within minutes or sooner to radiation fluctuations and that FCO2 was related almost linearly to gcw. Results are discussed in terms of soil-plant-atmosphere continuum, and interpreted in terms of dynamic interactions between transpiration and plant water status. The clear inverse relationship between ET and elongation rate or stem diameter changes provides additional evidence supporting the validity of 5-min averaging for the BREB + technique.

An efficient in vitro organogenesis protocol for the endangered relic tree species Bretschneidera sinensis and genetic fidelity assessment using DNA markers.

Bretschneidera sinensis is a monotypic species of rare and tertiary relic trees mainly distributed in China. B. sinensis is a potentially valuable horticultural plant, which has significant ornamental and research value, and is a crucial tool for the study of phylogeography. The artificial cultivation of B. sinensis is of great scientific value and practical significance. In this study, we developed a direct organogenesis process of B. sinensis using mature zygotic embryos as initial materials. The highest sterile germination induction (54.5%) from the mature zygotic embryo was obtained in a Murashige and Skoog (MS) medium with 2.0 mg·L-1 6-benzylaminopurine (6-BA) and 0.2 mg·L-1 α-naphthaleneacetic acid (NAA). The highest percentage of shoot regeneration (90.37%) was attained using 1.0 mg·L-1 6-BA and 0.01 mg·L-1 NAA in the MS medium. The Woody Plant Medium (WPM) had the greatest adventitious shoot elongation rate of 93.33%. The most optimized rooting rate was 88.89% in a half-strength MS medium containing 2.0 mg·L-1 indole-3-butyric acid (IBA) and 1.0 mg·L-1 NAA. The genetic fidelity of in vitro regenerated plantlets was assessed using inter-simple sequence repeats and random amplified polymorphic DNA molecular markers, confirming the genetic uniformity and stability of regenerated B. sinensis plantlets. Our research presents an effective in vitro propagation system for B. sinensis, laying the groundwork for its germplasm conservation and large-scale production while maintaining high genetic integrity.

Evaluation of rapeseed (Brassica napus L.) genotypes for tolerance to PEG (polyethylene glycol) induced drought at germination and early seedling growth

Rapeseed (Brassica napus L.) is an important oilseed crop well adapted to Mediterranean area. However, increasing drought, due to climate change, impairs its growth and development, mainly when this stress occurs early during germination. This study carried out in vitro conditions aimed to investigate the effect of water deficit on seed germination and seedling growth traits in 12 genotypes to select the most drought-tolerant ones. Drought conditions were created using polyethylene glycol 6000 to induce three osmotic potential levels, namely −0.7 MPa for moderate stress, −0.9 MPa for intermediate stress, and −1.1 MPa for severe stress. Germination percentage (GP), germination rate (GR), mean germination time (MGT), root length (RL), shoot length (SL), root-to-shoot ratio (RSR), seedling vigor index (SVI), shoot elongation rate (SER), and root elongation rate (RER) were measured/calculated. ANOVA and PCA were performed to analyze the data gathered. Results showed a significant effect of genotype, drought, and drought × genotype interaction on all studied parameters. Under severe drought conditions, overall values of GP, GR, RL, SL, SER, RER, and SVI decreased by 87.15 %, 53.29 %, 9.33 %, 4.73 %, 78 %, 82 %, and 96 %, respectively, while those of MGT and RSR increased by 56 % and 76 %, respectively, when compared to unstressed conditions. However, the genotypes studied reacted differently to the three levels of water stress. Based on PCA results, RL, RER, and GP proved to be the most discriminating of drought-tolerant genotypes. Overall, higher drought tolerance was associated with higher values in RL, SL, and SVI. Accordingly, the variety ‘Nap10’ and, to a lesser extent, ‘Baraka’ and ‘Nap9’ exhibited higher drought tolerance than the rest of genotypes, which makes them potential cultivars for dry areas. However, further studies in real field conditions are needed to confirm their tolerance to drought occurring at germination as well as during other stages, mainly flowering.

Effect of Shoot Bending at Different Time on Production and Quality of Hybrid Tea Rose Cultivar Minu Pearle

A field experiment was undertaken from September to March for two consecutive years (2020 and 2021) to find out the best time for shoot bending in Hybrid Tea rose. Growth and development of rose cultivar Minu Pearle, was significantly influenced by shoot bending at different time (4th week of September to 4th week of December). Among the treatments tallest plants & maximum leaf area was produced in plants bended on T5 whereas, the plant canopy was registered to be maximum in 2nd week of December. The highest rate of shoot elongation at 15 & 30 days after shoot bending was noted in second week of November and October respectively. Application of shoot bending on 2nd week of October recorded early blooming and slowest flower bud emergence was registered in T5whereas, delayed sepal reflex and maximum days taken to attain cup shape was observed in T6. In terms of flower quality parameters like length and diameter of flower bud and pedicel and weight of individual flower, T5 proved to be superior. Shoot bending applied on 2nd week of November (T4) produced long and thick stalks. Among the treatments maximum number of flowers, longest self and vase life, highest dry matter production from leaves and stem, greater chlorophyll and anthocyanin content was observed in T5.

Regeneration of Raja (Musa AAB Group) and Kepok (Musa ABB Group) bananas on various stages of in vitro culture

Banana group can be divided into two groups based on their method of its utilization. Banana group that can be eaten immediately after ripening is called "dessert banana", e.g., Raja, while the group that needs particular processing before consumption is called "plantain banana", e.g., Kepok. This study aimed to compare the growth of Raja banana with Kepok plantain through experiments at three stages of the in vitro culture media: the shoot initiation, shoot multiplication, and plantlet acclimatization, also to compare the growth of Raja bananas with Kepok plantains in response to cytokinins BAP and TDZ at shoot multiplication stage. Planting material was in the form of rhizomes that was prepared with the same size. The experiment was performed using a completely randomized design. Results showed that Kepok plantain could adapt faster to the media condition than Raja banana; the phenomenon was evident in the growing speed of Kepok during shoot initiation stage. The proportion of the B genome did not show a direct effect on shoot induction at the multiplication stage or enlargement and organ formation at the acclimatization stage. Shoot induction at the multiplication stage depended more on the composition of the media used. The combination of BAP 3 mg L-1 and TDZ 0.01 mg L-1 in MS media produced the best shoot induction rate, and TDZ 0.01 mg L-1 in MS media had the highest shoot elongation rate.
 Keywords: banana, BAP, genome, PGR, plantain, TDZ

Characterization of Rice Genotypes for SNORKEL1 (SK1) and SNORKEL2 (SK2) Gene

The present study was performed in kharif (June-December) 2019 at Bihar Agricultural College, Sabour, Bhagalpur, Bihar, India to screen gene specific markers developed from SNORKEL1 (SK1) and SNORKEL2 (SK2) gene and identify the rice genotypes for the presence of SNORKEL genes. A total of 13 rice genotypes were used out of which 8 genotypes Vaidehi, RYC743, FR13A, Desaria, Dudhi, Birar, Kalaladora and Kajargod indicated the presence of both SNORKEL1 (SK1) and SNORKEL2 (SK2) gene using SK1-1, SK1-2, SK2-1 and SK2-2 markers. Therefore, these genotypes have tolerance ability of deep water flooding due to higher rates of elongation where water stagnates for longer than two weeks. However, results from the present study also revealed that the genotype Desaria and RYC743 had higher rates of elongation and Satyam, Sudha, Purnendu, FR13A, Pansoradhan and Swarna Sub1 had lower shoot elongation rate compared to other genotypes. This study provides gene specific markers for the identification of varieties/donors tolerant to deep water flooding as well as donors to be used in deep water rice breeding programs. Thus, the marker developed and validated in this study will aid rice breeders in quickly and efficiently identifying and introgressing the SNORKEL genes. The results would be a helpful in the development of rice varieties with both submergence tolerance and elongation ability in order to improve the yield stability in flood-prone areas.

Seed Priming Treatments to Improve Heat Stress Tolerance of Garden Pea (Pisum sativum L.)

Heat stress seriously affects the production of cool-season food legume crops such as garden peas. Seed priming is a widely used technique that increases germination and improves plant growth and development, resulting in better field performance and higher yield of crops. In the current study, we investigated three seed priming treatments—hydropriming (dH2O), osmopriming (2.2% w/v CaCl2), and hormopriming (50 mg L−1 salicylic acid—SA)—and their effect on germination, initial seedling development, and physiological traits of two novel garden pea cultivars, under optimal conditions and heat stress. Seed priming with H2O, CaCl2, and SA enhanced garden pea performance under both optimal and stress conditions via significant improvements in germination energy, final germination, mean germination time, mean germination rate, seedling vigor index, shoot length, root length, fresh seedling weight, dry seedling weight, shoot elongation rate, root elongation rate, relative water content, chlorophyll content, and membrane stability index, as compared to control. The highest effect on the examined parameters was achieved by osmopriming and hormopriming in both cultivars, suggesting that these treatments could be used to improve the heat stress tolerance of garden pea, after extensive field trials.

Adaptive responses to flooding in wild rice species with various genomes other than AA

ABSTRACT In the present study, 15 accessions of wild rice species belonging to genome groups different from that of Oryza sativa were tested for their adaptive response to flooding at the seedling and mature stages. Under complete submergence at the seedling stage, reduced underwater shoot elongation and high survival rate after the recovery period were observed in the accessions of O. minuta as well as tetraploid O. punctata, O. eichingeri, O. officinalis, O. alta, O. grandiglumis, O. latifolia, and O. australiensis. This suggests that these species exhibit submergence tolerance at the seedling stage. During gradual submergence at mature stage, promoted internodal elongation was observed in the accessions of diploid and tetraploid O. punctata, O. alta, O. grandiglumis, O. latifolia, and O. brachyantha. This suggests that these species possess floating ability. Remarkably, two CCDD genome species, namely O. grandiglumis and O. latifolia, strongly displayed both submergence tolerance at the seedling stage and floating ability at mature stage, suggesting that these species are valuable genetic resources for improving rice adaptability to flooding. SUB1A and SNORKEL genes are known to confer submergence tolerance and floating ability to O. sativa, respectively. However, SUB1A, SNORKEL1, and SNORKEL2 genes were not detected in any of the wild rice accessions investigated in the present study. Our results suggest that adaptive responses to flooding in the investigated wild rice species can be achieved independently of the presence or absence of SUB1A and SNORKEL genes.

Chickpea and lentil show little genetic variation in emergence ability and rate from deep sowing, but small-sized seed produces less vigorous seedlings

Context Germination and emergence are key to successful annual crop establishment. Emergence rate depends on germination rate, sowing depth, and rate of pre-emergent shoot elongation. The rate at which a shoot grows prior to emerging from the soil becomes significant when crops such as chickpea (Cicer arietinum L.) and lentil (Lens culinaris Medik.) are deep sown to utilise moisture below the conventional sowing zone. Aims In seeds of contrasting size, we aimed to compare the ability of chickpera and lentil varieties to emerge from deep sowing. Here we describe genetic variation for epicotyl growth rate, and phenotypic variation for epicotyl and root growth rates and biomass partitioning, of chickpea and lentil, as they relate to seed size. We further assess the impact of deep sowing and soil type on emergence, establishment and yield of the two species. Methods Epicotyl elongation rates, root growth and seedling biomass partitioning were determined in controlled environment studies, using soil tubes. Field trials were conducted on two different soil types at two sowing depths. Key results Most of the variance in epicotyl growth rate could be attributed to species rather than variety. Although epicotyl emergence was faster in lentil, chickpea epicotyl growth rates were higher than those in lentils and unrelated to seed size, whereas growth rates in lentils were weakly correlated to seed size (r = 0.31). Root development and epicotyl diameter appeared to be traded for maintenance of growth in smaller seeds of both species. In the field, sowing depth did not affect emergence, establishment or yield of chickpeas at either site. Deeper sowing resulted in minor reductions in emergence of lentil at one site, although biomass and yield were not affected. Conclusions Emergence of both crops was unaffected by deep sowing (to at least 200 mm) under controlled environment and sandy field conditions. There was minimal genetic variation for the measured parameters within a species. Seed size was of little importance for emergence rate; however, shoot growth rate from small seeds was maintained by reducing seedling vigour. Implications Seed size should be considered when deep sowing lentils in order to maintain high seedling vigour. Further work is needed to understand how environmental factors influence seedling emergence from depth.

Variation in Growth Response of Coastal Dune-Building Grass Species Ammophila Arenaria and Leymus Arenarius to Sand Burial

AbstractAmmophila arenaria and Leymus arenarius are dune-building grass species native to European seacoasts. The present study aimed to compare growth responses to the sand burial of A. arenaria and L. arenarius from coastal habitats of the Baltic Sea, when the intensity of sand accretion was relatively low under controlled conditions. Plants were grown from seeds collected from natural coastal habitats, transplanted into individual containers, buried in the sand at different depths in the rapid shoot elongation stage, and further cultivated (11 or 9 weeks) in an automated greenhouse. Burial in sand significantly stimulated the growth of shoots of A. arenaria, the effect was earlier at high burial intensities (46 and 60%) and was evident ten days after the start of treatment. Both shoot and root dry mass increased for plants buried at 13%; however, increased burial depth (37, 46 and 60%) resulted in a significant increase in root biomass. In comparison, shoot biomass decreased significantly at the highest burial intensity (60%). For L. arenarius, there was no direct dependence of shoot elongation rate on burial depth. There was a tendency for increased elongation growth and biomass allocation to leaf sheaths despite a decrease in total shoot mass. Most strikingly, root biomass decreased with sand burial in parallel with increased burial depth up to 21% intensity. In conclusion, although both grass species showed a positive shoot growth response to moderate sand burial intensity, differences in individual responses at the morphological and physiological level indicate the existence of different genetically based adaptation strategies.

Is there evidence of local adaptation of Phragmites australis to water level gradients and fluctuation frequencies?

Greater differences in hydrologic conditions are expected between coastal and inland wetlands with global climate change. Local adaptation has been considered as a significant driver of intraspecific differentiation in heterogeneous habitats. The common reed Phragmites australis is a cosmopolitan wetland species with high genetic variability and adaptability. In our study, reeds collected from coastal and inland wetlands were subjected to three stable water level gradients and two fluctuation frequencies in a common garden experiment. We measured their aboveground and belowground biomass, height, density, stem diameter, leaf water potential, specific leaf area, and photosynthetic parameters. Our results showed that P. australis exhibited high tolerance to stable and fluctuating water levels up to 30 cm depth. Increased shoot elongation rate and water-use efficiency promoted the establishment of P. australis in flooding habitats. The common reeds in the high-frequency water level fluctuation had a shorter shoot height and a lower shoot density than those in the low-frequency one. The coastal populations performed better under high (30 cm) and low (0 cm) water levels than the inland populations, which preferred shallow water (15 cm). The adaptation strategies of coastal and inland reeds to fluctuation frequencies were no different. We concluded that local adaptation might occur in P. australis populations due to different water levels rather than fluctuation frequency in coastal and inland wetlands. Our findings could provide a theoretical basis on the effects of flooding on intraspecific variation of wetland plants in future environmental change scene.

APPRAISEMENT OF SALINITY STRESS ON GERMINATION AND SEEDLING DEVELOPMENT OF OKRA (Abelmoschus Esculentus L.)

Salt stress is one of the most common abiotic factors which has a trouble impression on the seed germination and establishment of crops. A laboratory based incubation experiment was executed at the department of Agriculture, Noakhali Science and Technology University during the period from January to February 2019 to investigate the salt stress effects on germination and seedling development of okra. The experiment comprises on okra variety named ‘Green Finger F1’.There were eight treatments viz. T0 (0 mM NaCl), T1 (20 mM NaCl), T2 (50 mM NaCl), T3 (100 mM NaCl), T4 (150 mM NaCl), T5 (200 mM NaCl), T6 (250 mM NaCl) and T7 (300 mM NaCl) and the experiment was designed at Completely Randomized Design (CRD) with three replications. Different parameters like germination percentage, speed of germination, seedling height, shoot elongation rate, shoot fresh and dry weight, root length, root fresh and dry weight and finally vigor index were compared among the all treatments. From the findings of this research trial, it can be extracted that the treatments T0 to T2 okra performed well as compare to the other treatments. So this study clearly indicated that the okra could be a promising crop for coastal areas and lead to improvements in agricultural production where mild saline condition present. However, it will not grow well under a high saline condition.

Metabolite profiling of semi-leafless pea (Pisum sativum L.) under progressive soil drought and subsequent re-watering

Four semi-leafless pea (Pisum sativum L.) cultivars at the vegetative stage of growth were exposed to progressive soil drought, which lasted for 18 days until the plants began to wilt, after which a 7-day period of the recovery from stress followed, when plant watering was resumed. The soil drought negatively affected plant growth, slowing down the rate of shoot elongation, decreasing the accumulation of fresh and dry weight, inhibiting the development of new leaves, and delaying the flowering of plants. Changes in the levels of 41 polar metabolites (identified by GC–MS) were established by the GC-FID method in the shoot tip, stem, stipules and tendrils, separately. Drought caused re-arrangement in the metabolism in all parts of the pea shoot, leading to a significant increase in the content of total polar metabolites. Although changes in most metabolites in the same parts of shoot were not identical among the pea cultivars studied, some metabolites were uniformly accumulated until 18th day of drought and decreased after recovery. They were i) proline and malate in all, while myo-inositol in most parts of shoot (of all the pea cultivars), ii) sucrose and glycine in the shoot tip, iii) homoserine in the stem and iv) GABA in stipules. These findings signify that the pea adjustment to progressive soil drought includes both accumulation of osmolytes and osmoprotectants and translocation of some of them (proline, sucrose, myo-inositol) to the shoot tip, thereby protecting the youngest tissues from damage caused by water deficit.

Clonal propagation of Dracaena fragrans cv. Victoria through tissue culture technology

Micropropagation of Dracaena fragrans cv.Victoria was conducted using the young, tender and disease-free leaves and nodal segments as explants collected from the local market of Savar, Dhaka. Surface sterilization of the explants pretreated with a liquid detergent and then 0.2% HgCl2 for 4-5 minutes produces maximum contamination free explants without any toxicity. After surface sterilization, different explants were inoculated on gelrite gelled MS medium supplemented with different concentrations of 2,4-D for callus induction and with different concentrations and combinations of BAP and NAA for direct shoot induction. Nodal explants showed high callus induction potentiality (80%) on MS medium supplemented with 1.5 mg/l 2,4-D. The highest frequency of direct shoot induction from nodal segment was 80% and the number of shoots per nodal segment was(5.28±1.17) when they were cultured on MS medium supplemented with 3.0 mg/l BAP and 0.3 mg/l NAA. The highest shoot multiplication (83.33%) with maximum number of shoot per unit callus (5.62±1.24) and maximum shoot length (3.27±0.82 cm) was observed when the nodal calli were transferred in gelrite gelled MS medium in combination with 4.5 mg/l BAP and 0.5 mg/l NAA. Additionally, the incorporation of 4% sucrose and 10% coconut water with the above mentioned medium showed the satisfactory shoot growth and development with an average 7.84±1.30 shoots per unit of callus which was 4.21±0.78 cm in length. Moreover, addition of 3.0 mg/l GA3 with the above mention medium showed highest rate of shoot elongation (5.83±2.31cm). For root induction, in vitro raised shoots were transferred onto half-strength of MS liquid medium augmented with different concentrations and combinations of auxins (IBA and NAA). Maximum rooting (75%) were observed in halfstrength MS liquid medium supplemented with 0.5 mg/l IBA. After appropriate rooting the plantlets were successfully acclimatized (85% survival) when they were cultured in polybag containing (1:1:1) garden soil, sand and compost mixture before transferred to soil. Regenerated plants were morphologically identical with mother plants and showed their uniform growth in field condition.
 Jahangirnagar University J. Biol. Sci. 8(2): 1-11, 2019 (December)

Remediation of hexavalent chromium in contaminated soil using amorphous iron pyrite: Effect on leachability, bioaccessibility, phytotoxicity and long-term stability

A large amounts of arable land is facing a high risk of hexavalent chromium (Cr(VI)) pollution, which requires remediation using a low toxic agent. In this study, the remediation effect of amorphous iron pyrite (FeS2(am)) on Cr(VI) in Cr(VI)-contaminated soil was evaluated by systematically analyzing the variation of the leachability, bioaccessibility, phytotoxicity, and long-term stability of the remediated soil. The effectiveness of FeS2(am) on the leachability was assessed by alkaline digestion and the toxicity characteristic leaching procedure (TCLP); the effect on the bioaccessibility was evaluated via the physiologically based extraction test (PBET) and the Tessier sequential extraction; the effect on the phytotoxicity was assessed via phytotoxicity bioassay (seed germination experiments) based on rape (Brassica napus L.) and cucumber (Cucumis Sativus L.), and the long-term stability of the Cr(VI)-remediated soil was appraised using column tests with groundwater and acid rain as the influents. The results show that FeS2(am), with a stoichiometry of 4× exhibited a high efficiency in the remediation of Cr(VI) and decreased its leachability and bioaccessibility during the 30-day remediation period. In addition, seed germination rate, accumulation and translocation of Cr, and root and shoot elongation of rape and cucumber of remediated soil are not significantly different from those of clean soil, illustrating that FeS2(am) is suitable for remediating Cr(VI) contaminated arable soil. The stabilization of Cr(VI) in contaminated soil using FeS2(am) was maintained for 1575 days. The long-term effectiveness was further confirmed by the increasing amount of free Fe and Mn in the effluent and the decreasing redox potential. In summary, FeS2(am) has an excellent efficiency for the remediation of Cr(VI), demonstrating it is a very promising alternative for use in the contaminated arable soil.

Mulberry (Morus spp.) growth analysis by morpho-physiological and biochemical components for crop productivity enhancement

Mulberry is a crop of economic importance in sericulture and the silkworm solely feeds on its foliage for silk biosynthesis. The study reports characterization of mulberry growth by statistical analysis using morpho-physiological and biochemical components during three cultivation periods. Repeated measures ANOVA revealed significant variations (p < 0.001) of traits during the cultivation periods. The shoot elongation rate (SER) was maximum in 16 – 45th day of the growth phase across three cultivation periods. Inter-nodal distance (IND) was highly heritable and consistent in all environments. The photosynthetic rate (A) was highest in 45th day followed by 60th and 69th days. The stomatal conductance (gs) and transpiration rate (Tr) was uniform in different growth stages with no clear trend on intrinsic water-use efficiency (IWUE). A strong positive correlation of A, gs and Tr and, a negative correlation of number of days for bud sprouting (NDBS) and IWUE with fresh biomass (FB) were observed. The liner mixed model also suggested the contribution of few morpho-physiological traits in fresh leaf weight (FLW) and fresh shoot weight (FSW). Significant correlations (p < 0.05) of light and CO2 curve parameters (Amax, AQL, Vcmax and Jmax) with fresh biomass were established. The results of growth analysis augment crop cultivation practices and breeders are provided with better insight into the mulberry growth for strategic planning in productivity enhancement.

Reaction of some rapeseed (Brassica napus L.) genotypes to different drought stress levels during germination and seedling growth stages

Drought is a major abiotic stress that affects seed germination and plant growth in arid and semi-arid regions. Rapeseed is an oilseed crop adapted to Mediterranean area; however, it is reported that it is sensitive to water stress occurring during seed germination. In this study, we investigated how seed germination and early seedling growth of six rapeseed genotypes were influenced by different water stress levels. In addition to the control (absence of drought stress), three drought levels were simulated using three osmotic potentials of polyethylene glycol (PEG-6000), −9, −10 and −11 bars. A completely randomized design with three replications was used for this experiment. Germination percentage (GP), shoot length (SL), root length (RL), shoot elongation rate (SER) and root elongation rate (RER) were determined to evaluate the genotypes response to PEG-induced drought stress. Results showed drought stress, genotype and interaction stress × genotype had a significant effect on the studied parameters. GP decreased with the increase in stress level. The genotype ‛Nap9’ was the most interesting, having the highest GP values, namely 63.33, 62.67 and 28% under the stress levels −9, −10 and −11 bars, respectively. The genotype ‛H2M-5’, which ranked second with respect to this parameter, was statistically comparable to ‛Nap9’. Also, SL, RL, SER and RER decreased with the increase in drought stress level. However, the studied genotypes reacted differently to various water stress levels. Once again, the genotype ‛H2M-5’ exhibited the highest average RL and RER under all drought levels. Particularly, for severe drought conditions (−11 bars), ‛H2M-5’ had an average RL of 1.54 cm and RER of 0.36 cm/d. Field evaluation under controlled conditions is needed to confirm findings of the present experiment. The mutant ‛H2M-5’ could be a valuable and promising germplasm for developing a performant and adapted variety to be designed for harsh environments particularly characterized by early drought coinciding with germination and seedling growth stages.

Evaluation of the effectiveness of in situ stabilization in the field aged arsenic-contaminated soil: Chemical extractability and biological response.

The effectiveness of in situ stabilization in the long-term As-contaminated soil was assessed. In situ stabilization of As was conducted through a Fe-based sorbent amendment. Chemical extractability of As was first determined by solubility/bioavailability research consortium extraction method and any change in human health risk through oral ingestion was characterized. Also, nonspecifically bound As in soil was determined by five-step sequential extraction. The results indicate that such extractable fractions of As decreased, and consequently risk through oral ingestion decreased probably due to hematite transformed from both the goethite in the original soil and the Fe-based sorbent, which was identified through the X-ray absorption spectroscopy. In ecotoxicity test with Hordeum vulgare, root and shoot elongation and germination rate decreased which was contrary to the chemical extraction data. Such increase in As toxicity is because of increased exchangeable Ca2+ concentration causing As accumulation in the membrane surface of H. vulgare. Also, adsorption of phosphorus onto the Fe-based sorbent decreased available phosphorus concentration causing phosphorus deficiency for growth. Our results demonstrate that the effectiveness of in situ stabilization should be evaluated by means of both chemical extractability and biological response, as chemical analysis alone may not be sufficient to assess the ecotoxicity.