Decreased Root Length Research Articles

Response of selected okra cultivars to Meloidogyne incognita

Root–knot nematodes (Meloidogyne spp.) are major pests of vegetables especially in the tropics and subtropics. All commercial okra varieties are susceptible to root knot nematodes and cause substantial losses. The objective of this study is to find out resistant germplasm in order to facilitate our breeders for gene manipulation. A greenhouse study was conducted to evaluate 28 okra cultivars against Meloidogyne incognita inoculated with 5000 eggs. Five cultivars (Bamya Yalova, 19,232, 19,236, 1,922,121, and Green Wonder) had significantly fewer root galls and eggs and less reduction in plant growth (shoot weight and root length), than most of the other entries. A positive relationship was demonstrated between root galls and reduction in plant growth parameters measured. These cultivars may improve okra production in fields infested with M. incognita. During our study, none of the cultivars tested were observed to be immune or resistant to nematode infection according to a scale where: good host [susceptible] when Pf/Pi (Pf = Final population of nematodes after harvest and Pi = Initial population of nematodes which was used as inoculum during experiment) > 5.0, fair, better [moderately resistant] if 5.0 ≥ Pf/Pi > 1, poor if 1 > Pf/Pi > 0, and non-host [resistant] when Pf/Pi = 0. The cultivars, including 19,224, 19,235, Pusa Sawami, Ikra-1, Ikra-2 and Sabzperi China Red, were found to be susceptible with Pf/Pi > 5.0, and they were declared as good hosts of M. incognita. While all the other cultivars were moderately resistant, with 0 ≥ Pf/Pi > 1 but still a significant penetration of nematodes was found. The regression studies showed positive and significant relationships between the number of galls and the reduction in shoot weight (r2 = 0.95), number of galls and reduction in shoot length (r2 = 0.81), and number of galls and decrease in root length (r2 = 0.89).

Seedling growth of maize (Zea mays L.) inbred lines affected by seed treatment with pesticides

Seed treatment is a common way of fungicide and insecticide use nowadays, since this way of pesticide application can provide the best protection in the vicinity of the future plant. The aim of research was to evaluate the effects of different seed treatments on germination and seedling growth in three maize inbred lines. The research included the seed treatment with several combinations of a fungicide Maxim XL 035-FS (a.i. metalaxil-M + fludioxonil) and neonicotinoid insecticides Gaucho 600-FS (a.i. imidacloprid) and Cruiser 350-FS (a.i. thiamethoxam), as well as untreated seed (control). The results indicated that inbred lines 21202 x 21101 NS and 317659 NS had a highly vigourous seed which was not affected by the seed treatments. The seed treatments with Maxim XL 035- FS+Gaucho 600-FS and Maxim XL 035-FS+Cruiser 350-FS led to a decrease in germination (90.25% and 89.50%, respectively) of maize inbred line 306081 NS as well as a decrease in root length (126.75 mm and 125.25 mm, respectively) and dry root weight (0.135 g and 0.1875 g, respectively) of maize inbred line 21202 x 21101 NS. All seed treatments had positive effects on root growth, as well as on fresh root weight of maize inbred lines 306081 NS and 317659 NS.

Allelopathic effect of some aromatic plants on weed seeds

Allelopathic effect of cogermination of aromatic plant seeds [basil (Ocimum basilicum), coriander (Coriandrum sativum), lovage (Levisticum officinale), oregano (Origanum vulgare)] and weed seeds [hoary cress (Cardaria draba), scentless mayweed (Tripleurosperum inodorum)] on germination and early growth of weeds was investigated under laboratory conditions. Basil, coriander and lovage reduced germination of hoary cress from 13.8 to 27%. On the contrary, all aromatic plants, except lovage, had stimulatory effect on germination of scentless mayweed. Coriander decreased root length of hoary cress and scentless mayweed for 17.5 and 16.5%, respectively. Shoot length of scentless mayweed was increased in cogermination with all aromatic plants. Only lovage had significant inhibitory effect on fresh weight of hoary cress, while fresh weight of scentless mayweed was increased by coriander.

Influence of Zinc Oxide Nanoparticles on Cadmium Toxicity on Germination of Faba Bean (Vicia faba L.)

This work aimed to study the influence of zinc oxide nanoparticles (ZnONPs) on Cadmium (Cd) toxicity ongermination of Faba bean (Vicia faba L.). The results indicated that, the levels of Zn and Cd significantly increased inshoot and root in a correlation with their dose. The levels of shoot and root Cd decreased in plants treated with theincreasing of ZnONPs dose. ZnONPs and/ or Cd increased the shoot length, shoot fresh weight and shoot dry weightand whereas decreased root length, root length /shoot length and root dry weight in comparison with the control.ZnONPs and/ or Cd decreased the Mean Daily Germination MDG, Germination Index GI, Coefficient of Velocity ofGermination CVG, Promptness index PI, Germination stress tolerance index GSI, Seedling vigor index SVI and Rootlength stress tolerance index RLSI whereas increased Mean Germination Time MGT in comparison with control.ZnONPs at 250 mg L-1 with Cd 50 mg L-1 showed the highest decrease in MDG, GI, CVG, PI and GSI whereas MGTrecorded highest values. The highest decreased in SVI was shown in ZnONPs at 500 mg L-1 with Cd 25 mg L-1.Meanwhile, the highest decreased in RLSI was shown in ZnONPs at 1000 mg L-1 with Cd 50 mg L-1. It can beconcluded that, ZnONPs decreased Cd level in the seedling of Faba bean, as well as germination parameters whereasincreased some growth parameters.

Effects of Grafting Methods and Root Excision on Growth Characteristics of Grafted Muskmelon Plants

Grafting has been used for controlling certain soilborne diseases and improving abiotic stress tolerance in muskmelon (Cucumis melo) production. Grafting methods may vary considerably among geographic regions and nurseries, while excision of rootstock roots before graft healing may also be practiced, which allows root regeneration of the grafted plants. In this greenhouse study, four grafting methods including hole insertion, one-cotyledon, noncotyledon, and tongue approach methods were examined for their impacts on plant growth and root characteristics of ‘Athena’ muskmelon grafted onto ‘Strong Tosa’ interspecific hybrid squash rootstock (Cucurbita maxima × C. moschata). Nongrafted rootstock and scion plants were included as controls. Both the grafted and nongrafted plants were examined with or without root excision. The practice of root excision was unsuccessful with the tongue approach method, while it did not exhibit significant effects on graft quality and growth of plants grafted with the one-cotyledon and hole insertion methods. Grafted plants with root excision started to show active and rapid root regeneration at 8 days after grafting (DAG) and reached similar root length and surface area as the root-intact plants at 16 DAG. Plants grafted with the noncotyledon method showed a different root growth pattern with decreased root length and surface area at 16 DAG. As a result, this method reduced the quality of grafted plants. No significant differences in plant growth characteristics were observed among the hole insertion, one-cotyledon, and tongue approach grafted plants.

Effectiveness of exogenous salicylic acid on root and shoot growth attributes, productivity, and water use efficiency of water-deprived fennel genotypes

This study was carried out to investigate the response of fennel (Foeniculum vulgare Mill.) to water deficit and exogenous application of salicylic acid (SA). Six fennel genotypes, from Iran (namely ‘Urmia’, ‘Hamadan’, ‘Kerman’, ‘Shiraz’, ‘Birjand’ and ‘Yazd’) were subjected to two levels of irrigation consisting of either irrigation after 35% (control) or 75% depletion of available soil water (water deficit) and 3 levels of treatment with SA (0.0, 0.5 and 1.0 mM). Root growth attributes, yield and yield components as well as irrigation water use efficiencies for seed, oil and dry masses of the shoot and whole plant were studied. Shoot dry mass, grain yield and essential oil yield were decreased due to water deficit. Furthermore, root growth attributes were decreased under water deficit, except for root diameter and dry mass, and root/shoot ratio. With the exception of irrigation water use efficiency for seed yield, all irrigation water use efficiency aspects were increased when fennel was subjected to water deprivation. Fennel genotypes were grouped according to their stress susceptibility indices (SSI) into drought-tolerant, moderately drought-tolerant and drought-sensitive groups. The largest drought-induced decreases in root length, root dry mass, root length density, number of fruits per umbel, seed yield, 1000-seed weight, seed essential oil yield, and irrigation water use efficiency for seed and oil yield were observed in genotype ‘Hamadan’ from the drought-sensitive group. Salicylic acid led to increases in root growth and yield attributes, seed essential oil content and yield, and irrigation water use efficiency aspects under both moisture conditions. Overall, foliar application of SA appeared to attenuate the negative effects of drought stress on fennel through increases in most of the root growth and yield attributes and the attenuation was more substantial in the drought-tolerant set of fennel genotypes.

Phenotype of Arabidopsis thaliana semi-dwarfs with deep roots and high growth rates under water-limiting conditions is independent of the GA5 loss-of-function alleles.

Background and Aims The occurrence of Arabidopsis thaliana semi-dwarf accessions carrying inactive alleles at the gibberellin (GA) biosynthesis GA5 locus has raised the question whether there are pleiotropic effects on other traits at the root level, such as rooting depth. In addition, it is unknown whether semi-dwarfism in arabidopsis confers a growth advantage under water-limiting conditions compared with wild-type plants. The aim of this research was therefore to investigate whether semi-dwarfism has a pleiotropic effect in the root system and also whether semi-dwarfs might be more tolerant of water-limiting conditions.Methods The root systems of different arabidopsis semi-dwarfs and GA biosynthesis mutants were phenotyped in vitro using the GROWSCREEN-ROOT image-based software. Semi-dwarfs were phenotyped together with tall, near-related accessions. In addition, root phenotypes were investigated in soil-filled rhizotrons. Rosette growth trajectories were analysed with the GROWSCREEN-FLUORO setup based on non-invasive imaging.Key Results Mutations in the early steps of the GA biosynthesis pathway led to a reduction in shoot as well as root size. Depending on the genetic background, mutations at the GA5 locus yielded phenotypes characterized by decreased root length in comparison with related wild-type ones. The semi-dwarf accession Pak-3 showed the deepest root system both in vitro and in soil cultivation experiments; this comparatively deep root system, however, was independent of the ga5 loss-of-function allele, as shown by co-segregation analysis. When the accessions were grown under water-limiting conditions, semi-dwarf accessions with high growth rates were identified.Conclusions The observed diversity in root system growth and architecture occurs independently of semi-dwarf phenotypes, and is probably linked to a genetic background effect. The results show that there are no clear advantages of semi-dwarfism at low water availability in arabidopsis.

SCREENING OF PHYTOTOXIC EFFECT OF PESTICIDE BI-58 WITH USE OF <i>ALLIUM CEPA</i> L. AND <i>ZEA MAYS</i> L.

We carried out the comparative analysis of phytotoxic effect of BI-58 pesticide on morphometric indicators of roots of seeds of Zea mays L. and Allium cepa L. Results of the conducted research showed that BI-58 in the range of the studied concentrations (0,05 - 0,4 ml/l) had the negative impact on sprouts of Allium cepa and Zea mays' seeds which is shown in inhibition of a root gain and viability of seeds. This influence had the expressed dose-dependent character: increase of concentration of the tested preparation caused decrease in the studied indicators in both test cultures. The dose of 0,05 ml/l of phytotoxic action didn't render on sprouts of Allium cepa and Zea mays. It should be noted the concentration of BI-58 recommended for application (0,1 ml/l) had the expressed phytotoxic effect on test plants. It was established sprouts of Zea mays were more sensitive to toxic effect of pesticide, than Allium cepa. On the basis of these data this dose at cultivation of the tested cultures was recommended not to use. The further increase in concentration of BI-58 (0,2 and 0,4 ml/l) caused the interfaced increase of phytotoxic effect on Самарский научный вестник. 2015. № 2(11) 136 Д.Э. Эмирова СКРИНИНГ ФИТОТОКСИЧЕСКОГО ДЕЙСТВИЯ ПЕСТИЦИДА БИ-58 ... the tested cultures. Length of roots of Allium sera decreased by 1,5 times at concentration of 0,2 ml/l and by 40,66% - at decrease in quantity of the sprouted seeds. The increase in concentration of a preparation (0,4 ml/l) caused decrease in length of roots of sprouts of the studied test culture and oppression of their viability. In particular, length of roots of Allium sera in this option of research decreased by 1,8 times in comparison with control, a viability indicator - by 46,16%. Pesticide had similar impact on Zea mays. In particular, at a dose of BI-58 of 0,2 ml/l length of backs of Zea mays decreased by 45,1%, a viability indicator - for 25,3% in comparison with control. The increase in concentration of the studied preparation twice (0,4 ml/l) caused decrease of the morforometric roots indicators for 52,1%, decrease in viability - for 28,8% in comparison with control option.

Morpho-anatomical and growth alterations induced by arsenic in Cajanus cajan (L.) DC (Fabaceae)

Arsenic (As) is a toxic element to most organisms. Studies investigating anatomic alterations due to As exposure in plants are scarce but of utmost importance to the establishment of environmental biomonitoring techniques. So, this study aimed to investigate the effects of As on the development and initial root growth in Cajanus cajan (Fabaceae), characterize and quantify the possible damages, evaluate genotoxic effects, and identify structural markers to be used in environmental bioindication. Plants were exposed hydroponically to 0.5, 1.0, 1.5, and 2.0 mg As L(-1), as sodium arsenate. Growth parameters were measured, and in the end of the exposure, root samples were analyzed for qualitative and quantitative anatomical alterations. Arsenic genotoxicity was evaluated through analysis of the mitotic index in the root apex. Compared to the control, As-treated seedlings showed an altered architecture, with significantly decreased root length (due to the lower mitotic index in the apical meristem and reduced elongation of parenchyma cells) with darkened color, and abnormal development of the root cap. A significant increase in vascular cylinder/root diameter ratio was also detected, due to the reduction of the cellular spaces in the cortex. The secondary xylem vessel elements were reduced in diameter and had sinuous walls. The severest damage was visible in the ramification zone, where uncommon division planes of phellogen and cambium cells and disintegration of the parenchyma cells adjacent to lateral roots were observed. The high sensibility of C. cajan to As was confirmed, since it caused severe damages in root growth and anatomy. The main structural markers for As toxicity were the altered root architecture, with the reduction of the elongation zone and increase of ramification zone length, and the root primordia retained within the cortex. Our results show a new approach about As toxicity and indicate that C. cajan is a promising species to be used for bioindication of environmental contamination by As.

Low pH-induced changes of antioxidant enzyme and ATPase activities in the roots of rice (Oryza sativa L.) seedlings.

Soil acidification is the main problem in the current rice production. Here, the effects of low pH on the root growth, reactive oxygen species metabolism, plasma membrane functions, and the transcript levels of the related genes were investigated in rice seedlings (Oryza sativa L.) in a hydroponic system at pH 3.5, 4.5, and 5.5. There were two hybrid rice cultivars in this trial, including Yongyou 12 (YY12, a japonica hybrid) and Zhongzheyou 1 (ZZY1, an indica hybrid). Higher H+ activity markedly decreased root length, the proportion of fine roots, and dry matter production, but induced a significant accumulation of hydrogen peroxide (H2O2), and led to serious lipid peroxidation in the roots of the two varieties. The transcript levels of copper/zinc superoxide dismutase 1 (Cu/Zn SOD1), copper/zinc superoxide dismutase 2 (Cu/Zn SOD2), catalase A (CATA) and catalase B (CATB) genes in YY12 and ZZY1 roots were significantly down-regulated after low pH exposure for two weeks. Meanwhile, a significant decrease was observed in the expression of the P-type Ca2+-ATPases in roots at pH 3.5. The activities of antioxidant enzymes (SOD, CAT) and plasma membrane (PM) Ca2+-ATPase in the two varieties were dramatically inhibited by strong rhizosphere acidification. However, the expression levels of ascorbate peroxidase 1 (APX1) and PM H+-ATPase isoform 7 were up-regulated under H+ stress compared with the control. Significantly higher activities of APX and PM H+-ATPase could contribute to the adaptation of rice roots to low pH.

Toxicity of sulfate and chloride to early life stages of wild rice (Zizania palustris).

Despite the importance of wild rice (Zizania palustris) in the Great Lakes region of North America, its sensitivity to sulfate is not well understood. A 21-d hydroponic experiment was performed to determine the toxicity of sulfate to wild rice seeds and seedlings. Effects of 6 sulfate concentrations ranging from 10 mg/L to 5000 mg/L and of chloride salts at equivalent conductivity were evaluated to determine whether adverse effects were attributable to sulfate or to conductivity-related stress. Sulfate treatment decreased root length, shoot length, and leaf number, and increased phytotoxic effects at concentrations of 5000 mg/L relative to a 50 mg/L control. The time to 30% mesocotyl emergence decreased at 2500 mg/L sulfate, indicating a potential stimulatory effect. Sulfate exposures of ≤ 5000 mg/L had no effect on 5 additional end points. Multiple regression analysis indicated that most observed changes could be attributed to conductivity-related stress rather than sulfate per se, with the exception of shoot length and leaf number. Chloride was more toxic than sulfate, as determined by root length and phytotoxicity. In summary, sulfate concentrations below 5000 mg/L did not adversely affect early-life stage wild rice during a 21-d period, and effects at 5000 mg/L sulfate were attributable to conductivity-related stress rather than sulfate toxicity in 2 of 4 end points.

Public-domain software for root image analysis

In the search for high efficiency in root studies, computational systems have been developed to analyze digital images. ImageJ and Safira are public-domain systems that may be used for image analysis of washed roots. However, differences in root properties measured using ImageJ and Safira are supposed. This study compared values of root length and surface area obtained with public-domain systems with values obtained by a reference method. Root samples were collected in a banana plantation in an area of a shallower Typic Carbonatic Haplic Cambisol (CXk), and an area of a deeper Typic Haplic Ta Eutrophic Cambisol (CXve), at six depths in five replications. Root images were digitized and the systems ImageJ and Safira used to determine root length and surface area. The line-intersect method modified by Tennant was used as reference; values of root length and surface area measured with the different systems were analyzed by Pearson's correlation coefficient and compared by the confidence interval and t-test. Both systems ImageJ and Safira had positive correlation coefficients with the reference method for root length and surface area data in CXk and CXve. The correlation coefficient ranged from 0.54 to 0.80, with lowest value observed for ImageJ in the measurement of surface area of roots sampled in CXve. The IC (95 %) revealed that root length measurements with Safira did not differ from that with the reference method in CXk (-77.3 to 244.0 mm). Regarding surface area measurements, Safira did not differ from the reference method for samples collected in CXk (-530.6 to 565.8 mm²) as well as in CXve (-4231 to 612.1 mm²). However, measurements with ImageJ were different from those obtained by the reference method, underestimating length and surface area in samples collected in CXk and CXve. Both ImageJ and Safira allow an identification of increases or decreases in root length and surface area. However, Safira results for root length and surface area are closer to the results obtained with the reference method.

English

The effect of elevated temperature on seed germination and seedling growth was investigated on three Nigerian cereal crops: maize, rice and sorghum. Seeds where then allowed to germinate in controlled growth at 37 (control: room temperature), 40, 42, 45 and 50°C and monitored for germination, shoot length and root length for 24, 48, 72 and 96 h, respectively. Seeds were also sown in small poly bags in triplicates under the same temperature regimes and assayed for the physiological effects on the root, stem and leaf for 2 weeks after germination. Results showed a decrease in germination rate as temperature regimes increased. There was significant increase in the shoot length of maize at 37 and 40°C after 96 h of exposure to these temperature regimes but a drastic decrease at 42, 45 and 50°C, respectively. Root length of the maize plantlets also decreased when exposed to 45 and 50°C, respectively. Sorghum plantlets also showed shoot increase at 37, 40 and 42°C temperature regimes but decreased at 45 and 50°C, while root length decreased in length at 42, 45 and 50°C, respectively. Rice plantlets exposed to different temperature regimes showed an increase in shoot length at 37, 40, 42 and 45°C, respectively with a decrease only at 50°C and also a decrease in root length at 50°C. The results from the seedling experiments showed a drastic reduction in physiological parameters tested when compared with the control at p < 0.05. Root length of maize reduced from 13.10 ± 1.5 at 40°C to 3.80 ± 0.5 at 50°C, while length of stem of sorghum reduced from 5.00 ± 0.4 to 3.40 ± 0.5. Rice had a reduction in leaf length of 6.70 ± 1.0 to 4.20 ± 1.5. The results of the experiments also showed that sorghum was most affected by the increased temperature range among the three test crops. This study clearly indicates that the growth of maize, rice and sorghum seedlings showed signs of stagnation or decrease following rise in temperature. As temperature rise is part of the global climate change problem, the study clearly shows that climate change vis a vis increase in temperature will have strong negative implications on food crops in the nearest future especially in emerging economies like Nigeria.   Key words: Cereal crops, climate change, elevated temperature, seed germination, seedling growth.

Screening of Fe-Deficiency Tolerance in Okra (<i>Abelmoschus esculentus</i> L.) Through Hydroponic Culture

Screening for Fe deficiency tolerance in okra (Abelmoschus esculentus) Bangladeshi genotypes (‘BARI-1’, ‘Local variety’, ‘Orca Onamica’, and ‘Prince’) were studied based on different morphological and physiological parameters. Number of leaves, shoot height and weight were significantly reduced in ‘Orca Onamica’ and ‘Prince’, whereas ‘BARI-1’ and ‘Local variety’ did not show prominent decrease in the aforesaid growth parameters under Fe deficiency. Again, ‘Orca Onamica’ and ‘Prince’ showed significantly decreased root length and root biomass under Fe deficiency. In contrast, these parameters were unchangeable in ‘BARI’-1 and ‘Local variety’ in Fe shortage compared to controls. Furthermore, Fe deficiency caused severe decrease in chlorophyll (a and b) and Fe concentrations in leaves of ‘Orca Onamica’ and ‘Prince’ grown on hydroponic culture. In contrast, chlorophyll (a and b) and Fe concentrations were not significantly decreased in ‘BARI-1’ and ‘Local variety’ due to Fe deficiency. Based on these findings, tolerance to Fe deficiency in these okra cultivars can be categorized as: tolerant (‘BARI-1’ and ‘Local’), and sensitive (‘Orca Onamica’ and ‘Prince’). The ranking can be applied in plant breeding program and may have great advantage over conventional methods. This study also demonstrates the effectiveness of hydroponic culture as an efficient method to screen Fe-efficient crop plants.

Screening of Fe-Deficiency Tolerance in Okra (<i>Abelmoschus esculentus</i> L.) Through Hydroponic Culture

Screening for Fe deficiency tolerance in okra (Abelmoschus esculentus) Bangladeshi genotypes (‘BARI-1’, ‘Local variety’, ‘Orca Onamica’, and ‘Prince’) were studied based on different morphological and physiological parameters. Number of leaves, shoot height and weight were significantly reduced in ‘Orca Onamica’ and ‘Prince’, whereas ‘BARI-1’ and ‘Local variety’ did not show prominent decrease in the aforesaid growth parameters under Fe deficiency. Again, ‘Orca Onamica’ and ‘Prince’ showed significantly decreased root length and root biomass under Fe deficiency. In contrast, these parameters were unchangeable in ‘BARI’-1 and ‘Local variety’ in Fe shortage compared to controls. Furthermore, Fe deficiency caused severe decrease in chlorophyll (a and b) and Fe concentrations in leaves of ‘Orca Onamica’ and ‘Prince’ grown on hydroponic culture. In contrast, chlorophyll (a and b) and Fe concentrations were not significantly decreased in ‘BARI-1’ and ‘Local variety’ due to Fe deficiency. Based on these findings, tolerance to Fe deficiency in these okra cultivars can be categorized as: tolerant (‘BARI-1’ and ‘Local’), and sensitive (‘Orca Onamica’ and ‘Prince’). The ranking can be applied in plant breeding program and may have great advantage over conventional methods. This study also demonstrates the effectiveness of hydroponic culture as an efficient method to screen Fe-efficient crop plants.

Morfología y bioactividad de la cianobacteria Leptolyngbya en los campos de cultivo de arroz

The genus Leptolyngbya comprises filamentous cyanobacteria that are important in rice fields. In the rhizosphere, cyanobacteria produce a variety of secondary metabolites such as auxins that are important in agriculture soil performance. To assess this, Leptolyngbya strain MMG-1, was isolated from the rhizosphere of rice plants and described. For this, the morphology of this strain was studied by light microscopy as well as by confocal laser scanning microscopy. Besides, the ability of this strain to synthesize an auxin-like bioactive com- pound was demonstrated under various culture conditions (different amounts of tryptophan; pH; different alter- nating light:dark periods; duration of the incubation). The auxin-like compound was extracted from the culture of Leptolyngbya strain MMG-1 and identified as indole-3-acetic acid (IAA) by thin layer chromatography (TLC) as well as by high performance liquid chromatography (HPLC). Our results showed that the strain required the precursor L-tryptophan for the synthesis of IAA. Leptolyngbya strain MMG-1 accumulated IAA intracellularly. The IAA secreted by Leptolyngbya strain MMG-1 was significantly correlated with the initial concentration of L-tryptophan in the medium, as well as with the duration of the incubation. The bioactivity of the secreted IAA was determined by its effect on the rooting pattern of Pisum sativum seedlings. The culture supernatant of Leptolyngbya strain MMG-1 stimulated the seedling lateral rooting, while it decreased root length. Hence, rhizospheric Leptolyngbya produced auxin under different conditions and affected the plants rooting pattern.

Alteration of root growth by lettuce, wheat, and soybean in response to wear debris from automotive brake pads.

Brakes from motor vehicles release brake pad wear debris (BPWD) with increased concentrations of heavy metals. Germination and root-elongation assays with lettuce, wheat, and soybean were used to provide an initial evaluation of the phytotoxicity of either a water extract of BPWD or BPWD particulates. In terms of germination, the only effect observed was that lettuce germination decreased significantly in the BPWD particulate treatment. Lettuce and wheat showed decreased root length and root-elongation rate in the presence of the BPWD particulates, whereas lettuce produced a significantly greater number of lateral roots in response to BPWD extract. There was no significant effect of either BPWD treatment on soybean root elongation or lateral roots. Treatment with BPWD extracts or particulates caused significant alterations in the bending pattern of the plant roots. These initial results suggest that BPWD may have effects on the early growth and development of plants.

Functional interplay between protein kinase CK2 and salicylic acid sustains PIN transcriptional expression and root development

We have previously reported that CK2-defective Arabidopsis thaliana plants (CK2mut plants) were impaired severely in root development and auxin polar transport, and exhibited transcriptional misregulation of auxin-efflux transporters (Plant J., 67, 2011a, 169). In this work we show that CK2mut roots accumulate high levels of salicylic acid (SA) and that the gene that encodes isochorismate synthase (SID2) is overexpressed, strongly suggesting that CK2 activity is required for SA biosynthesis via the shikimate pathway. Moreover, SA activates transcription of CK2-encoding genes and, thus, SA and CK2 appear to be part of an autoregulatory feed-back loop to fine-tune each other's activities. We also show that exogenous SA and constitutive high SA levels in cpr mutants reproduce the CK2mut root phenotypes (decrease of root length and of number of lateral roots), whereas inhibition of CK2 activity in SA-defective and SA-signalling mutants lead to less severe phenotypes, suggesting that the CK2mut root phenotypes are SA-mediated effects. Moreover, exogenous SA mediates transcriptional repression of most of PIN-FORMED (PIN) genes, which is the opposite effect observed in CK2mut roots. These results prompted us to propose a model in which CK2 acts as a link between SA homeostasis and transcriptional regulation of auxin-efflux transporters. We also show that CK2 overexpression in Arabidopsis has neither impact on SA biosynthesis nor on auxin transport, but it improves the Arabidopsis root system. Thus, unlike the outcome in mammals, an excess of CK2 in plant cells does not produce neoplasia, but it might be advantageous for plant fitness.

Effect of mutagenic agents on seed germination and vegetative growth of mustard (Brassica rapa)

The experiment was conducted to study the effect of mutagens (physical and chemical) on seed germination along with root and shoot lengths of two locally collected varieties of Brassica rapa denoted as variety-1 and variety-2 in in vitro condition. Seeds were treated with various concentrations of mutagenic agents; physical (gamma radiation), chemical (sodium azide) and combined (gamma radiation + sodium azide). The doses of gamma radiation were 100Gy and 200Gy, sodium azide concentrations were 100, 300 and 500ppm and for combination, 100Gy and 200Gy gamma irradiated seeds were further treated with 100, 300 and 500ppm sodium azide solution. After 7 days observation, 100% seed germination obtained from 100Gy gamma irradiated seeds of variety-1 and 500ppm sodium azide treated seeds of variety- 2. 100% seed germination was also found in 7 days in physical and chemical mutagen combinedly treated seeds of variety-1 from 100Gy gamma radiation + 100ppm sodium azide, 100Gy gamma radiation + 300ppm sodium azide and 200Gy gamma radiation + 100ppm sodium azide and in variety-2, from 100Gy gamma radiation + 500ppm sodium azide and 200Gy gamma radiation + 500ppm sodium azide. Maximum increased root length (avg. 3.8cm) was obtained from variety-1 combined treated (200Gy gamma radiation + 300ppm sodium azide) seeds and minimum decreased root length (avg. 1.0cm) was from variety-2 combined treated (100Gy gamma radiation + 100ppm sodium azide) seeds. Maximum increased shoot length (avg. 4.7cm) was obtained from variety-1 combined treated (200Gy gamma radiation + 100ppm sodium azide) seeds and minimum decreased shoot length (avg. 1.4cm) was obtained from variety-2 combined treated (100Gy gamma radiation + 100ppm sodium azide) seeds. DOI: http://dx.doi.org/10.3329/bjsir.v48i4.18274 Bangladesh J. Sci. Ind. Res. 48(4), 253-256, 2013

Localized salt accumulation: the main reason for cotton root length decrease during advanced growth stages under drip irrigation with mulch film in a saline soil

High salinity in soil can prevent root growth of most plants. To investigate soil salinity dynamics under drip irrigation with mulch film (DI) and its effects on cotton root length, we conducted field experiments in saline soil based on a monolith method using flooding irrigation with mulch film (FI) as a control at the Korla Experimental Station of the Xinjiang Academy of Agricultural Sciences, China in 2009 and 2010. The results showed that the total root length decreased 120 days after sowing (DAS) under DI, and was mainly centered in the 0–30 cm soil layer and at distances of 30–70 cm from the drip-lines. There was almost complete overlap in the area of root length decline and salt accumulation. In the soil depth of 0–30 cm and at distances of 30–70 cm from the drip-lines at 110 to 160 DAS in 2009 and 171 DAS in 2010, the electrical conductivity (EC) in all soil samples was at least 3 mS/cm and in some cases exceeded 5 mS/cm under DI treatment. However, EC barely exceeded 3 mS/cm and no reduction in root length was observed under FI treatment. Correlation analysis of soil EC and root length density indicated that the root length declined when the soil EC exceeded 2.8 mS/cm. The main reason for the decrease of root length in cotton under DI was localized accumulation of salinity.