An improved and efficient micropropagation of Eclipta alba through transverse thin cell layer culture and assessment of clonal fidelity using RAPD analysis

An improved and efficient in vitro regeneration system has been developed for Eclipta alba, a medicinally important plant, through transverse thin cell layer culture (tTCL). The transverse section of the nodal segment of field grown plants was used as tTCL explants for plant regeneration. Shoot multiplication from tTCL nodal explants was influenced by BAP and their interaction with Kin or NAA. MS medium containing 13.2 μM BAP and 4.6 μM Kin was most effective for shoot multiplication from tTCL nodal explants. Upon this medium, percent response for shoot proliferation was 100% with an average of 32.6 shoot buds per tTCL nodal explant. Regenerated shoots from tTCL nodal explants were rooted on the growth regulator free MS medium. The rooted plantlets were successfully acclimatized and established in soil with a survival frequency of 90-100%. Random amplified polymorphic DNA (RAPD) markers were used to evaluate the genetic fidelity of the micropropagated plants. RAPD profile analysis indicated that micropropagated plants were genetically similar to mother plant.     

Mycorrhizal fungi and growth and development of micropropagated Scutellaria integrifolia plants

Scutellaria species have been used in many traditional medical systems and is well known among the Native American tribes as a strong emmenagogue and as a female medicinal herb. The inoculation of arbuscular mycorrhiza fungi (AMF) into the roots of micropropagated plantlets could help not only mass propagate these species, but also help grow in marginal, phosphorus deficient soils. Leaves, shoot apices, and nodal segments from wild as well as from greenhouse-grown plants were used to initiate cultures in Murashige and Skoog (MS) medium supplemented with cytokinins benzyladenine (BA), kinetin, thidiazuron (TDZ), naphthalene acetic acid (NAA), and indole butyric acid (IBA) Among all the explants tested for shoot bud induction, only shoot tips and nodal explants were responsive. Explants swelled and became rough on the surface at the end of 3-week incubation with many green shoot buds. Two to 3 weeks after transfering to rooting media with or without IBA, all shoots developed roots. In vitro raised plants were acclimatized in a mist chamber and transferred to 6-l containers in the greenhouse to study the role of AMF on plant growth and development. Inoculation with AMF, showed positive effects on plant growth, particularly root development compared with the control plants. Among the five AMF strains tested, S3004 increased plant height and fresh weights of shoot, root, and seed.     

Rice root morphological traits are related to isozyme group and adaptation

Rice accessions from the International Rice Research Institute (IRRI) germplasm bank were evaluated for root traits of 40-day-old plants grown in soil in the greenhouse. The 136 accessions represented six groups defined on the basis of isozyme classification, with isozyme group six further subdivided on the basis of origin and morphology. An additional 28 rice cultivars were evaluated for seminal root xylem vessel diameter when grown in pots in a growth chamber. Rice groups differed in root thickness, root xylem vessel diameter, root:shoot ratio, and patterns of root distribution. Isozyme group 1, which corresponds generally to the indica subspecies, had thin, superficial roots with narrow vessels and a low root:shoot ratio. The other major isozyme group, group 6, comprising japonica types, was characterized by thick roots with wider vessels, a greater proportion of the root weight below 15 cm, and a larger root:shoot ratio. On an average, the bulu and temperate group 6 accessions were similar to the non-bulu types except that their root:shoot ratios and proportion of root weight above 15 cm were more similar to group 1. Group 2, with aus types from South Asia, was characterized by intermediate root thickness, but vertical root distribution and root:shoot ratio were more similar to group 6. The minor isozyme groups 3–5 were represented by few accessions, and in general, they had root thickness and root distribution profiles more similar to group 1 than to group 6. While significant differences were observed among isozyme groups for all the traits under study, there was significant variation within groups and groups overlapped for all traits measured. This study highlights the wide range of variability for constitutive root traits in rice. For example, root thickness ranged from 0.68 to 1.04 mm, seminal root xylem vessel diameters from 30 to 58 μm, root:shoot ratios from 0.05 to 0.21, and accessions had from 44 to 73% of the total root weight concentrated in the surface 15 cm of soil. For the 28 cultivars evaluated, root xylem vessel diameter was highly correlated with reported values of leaf epicuticular wax content (r=0.89). These values indicate the range of genetic variation within the rice genome for root morphological traits.     

Prevalence of potato yellow vein virus (PYVV) in Solanum tuberosum Group Phureja Fields in Three States of Colombia

Potato yellow vein virus (Crinivirus) causes leaf yellowing, is limited to the phloem and is transmitted by Trialeurodes vaporariorum and tubers. PYVV causes up to 50 % yield reduction in S. tuberosum. The prevalence of PYVV was established in Group Phureja in 2008 in the Colombian states of Cundinamarca, Antioquia and Nariño. The presence (S) or absence (NS) of symptoms was established in 24,930 plants. Symptom prevalence was as follows: Cundinamarca 0.74 %?±?0.03, Antioquia 5.4 %?±?12 and Nariño 6.2 %?±?0.11. Percentages of S plants were highly variable among different states and municipalities. PYVV was diagnosed by RT-PCR in a subsample of 1,545 plants from Cundinamarca and Nariño. RT-PCR showed that 2.4 %?±?8.3?×?10^?5 and 41 %?±?0.0009 % of the symptomless plants of Cundinamarca and Nariño respectively were positive. This suggests possible late infection of plants by the vector which did not have enough time to express symptoms, infections with two or more viruses or “virus latency”. PYVV symptomatic prevalence in Group Phureja was lower than that reported for Diacol-Capiro (Group Andigena), but increases if molecular results are taken into account. This is the first known study aimed at determining PYVV prevalence using molecular tools and extensively sampling of S.tuberosum Group Phureja plants in grower’s fields in three states and multiple municipalities of Colombia.     

Relationship between Shoot Elongation and Dry Matter Weight During Submergence in Oryza sativa L. and O. glaberrima Steud. Rice Cultivars

Abstract

Rice plants are damaged by flash floods with a rapid increase in water level caused by a heavy rain. However, rice plants cope with the flash floods either by an “escape strategy” involving rapid shoot elongation or by a “quiescence strategy” involving surviving under water with minimal activity. As we found in previous experiments, Saligbeli cultivar adapted well to flash floods through rapid shoot elongation. To understand the vigorous growth process during submergence, we studied the relationship between shoot elongation and changes in dry matter weight (DMW) during submergence. O. glaberrima Steud. cv. Saligbeli and O. sativa L. cv. Ballawé and IR 49830-7-1-2-2 were used. Saligbeli and Ballawé exhibit shoot elongation, and IR 49830-7-1-2-2 exhibits flash-flood tolerance due to the presence of the Sub-1 gene. Twelve-day-old seedlings were submerged for 7 days and the plant length and DMW were measured. The plant length ratio of submerged to control plants in Saligbeli was higher than that of other cultivars during 2-6 days of submergence but IR 49830-7-1-2-2 shoot elongation was inhibited by submergence. In all three cultivars, the elongation of the developing leaf sheath conferred shoot elongation during submergence. The plant length of all submerged plants showed a strong positive correlation with DMW of the leaves developed during submergence. Submerged Saligbeli and Ballawé showed strong negative correlations between DMW of the leaves developed before and during submergence (r = –0.786 for Saligbeli and –0.772 for Ballawé , P < 0.05), suggesting that the enhancement of shoot elongation during submergence is accomplished by using dry matter of the leaves developed before submergence. However, the correlation was not observed in the submerged IR 49830-7-1-2-2. Further details from studies using isotopes are also needed to understand the plant growth during submergence.     

Mycoparasitic Trichoderma viride as a biocontrol agent against Fusarium oxysporum f. sp. adzuki and Pythium arrhenomanes and as a growth promoter of soybean

Trichoderma viride was proved as an effective biocontrol agent against two fungal pathogens, Fusarium oxysporum f. sp. adzuki and Pythium arrhenomanes, infecting soybean. During an in vitro biocontrol test, Trichoderma showed mycoparasitism and destructive control against the tested fungal pathogens. Both the pathogens significantly influence the germination and P. arrhenomanes had a severe effect (only 5% germination). The root system of the soybean plant was poorly developed due to the infection and it exerted a negative influence on the nodulation and further growth phases of the plant. During pot assay along with biocontrol activity, Trichoderma showed growth promoting action on the soybean plant. Trichoderma enhanced growth of shoot and root systems and fruit yield after 12 weeks of growth. Pythium and Fusarium infected plants treated with Trichoderma had ∼194% and 141% more height than pathogens alone. The fruit yield treated with Trichoderma was ∼66 per plant whereas the yield was only 41 for a control plant. The plants infected with Pythium and Fusarium and treated with Trichoderma had fruit yields of 43 and 53 respectively and those were 5 and 1.6 times higher than plants infected with pathogens.     

Salt tolerance inSolanum kurzianum andS. tuberosum cvs Alpha and Russet Burbank

Summary The cultivated potatoSolanum tuberosum cvs Alpha and Russet Burbank and the wild speciesS. kurzianum were compared with respect to salt tolerance. Plants of the wild species were found to be more salt tolerant than those of the cultivated species since their growth was less impaired by the salinity, although they accumulated more sodium and less potassium ions in the shoot. Unlike the whole plant, callus derived from the wild plants was not more tolerant than that from the cultivated species. Differences in the responses to salinity between cultivated and wild plants, and between the whole plants and calli derived from them are discussed. Based on these differences and the similarity of the physiological responses to salt stress betweenS. kurzianum and the wild salt-tolerant relatives of tomato, the former is suggested as a potential source of genes for increasing the salt tolerance of potato.     

In vitro shoot regeneration and chromosome doubling in 2X and 3X potato clones

The possibility of scaling ploidy levels up and down offers several advantages for genetic studies and breeding work in potato. Shoot regeneration and chromosome doubling in plants regenerated fromin vitro cultures were investigated in 4 diploid (2n=2x=24) and 2 triploid (2n=3x=36) clones. Internode and leaf expiants were taken from plants propagated eitherin vitro as shoot cultures, orin vivo in a greenhouse. Two regeneration procedures were compared. Regeneration frequencies were significantly higher using a two-step regeneration protocol and from leaf explants, while doubling was more efficient starting fromin vivo grown plants. No doubling was observed in triploid clones. Considering altogether the percentage of regeneration and doubling, and the number of shoots regenerated per explant, the most efficient conditions were considered leaf explants taken fromin vivo grown plants, and cultured according to a two-step regeneration protocol.     

Effects of Exogenous Glycinebetaine on Growth and Ultrastructure of Salt-Stressed Rice Seedlings (Oryza sativa L.)

Abstract

The effects of exogenously applied glycinebetaine on the salt-stress-induced inhibition of growth and ultrastructural damages in rice seedlings were investigated. Glycinebetaine was not effective in alleviating the NaCl-induced inhibition of root growth and rather enhanced the NaCl-induced inhibition. However, it was found to alleviate the inhibition of shoot growth induced by NaCl stress. Concentrations of Na were higher in salt-stressed plants than in unstressed plants. Stressed plants receiving glycinebetaine had a significantly lower Na and higher K concentrations in the shoots than the plants grown without application of glycinebetaine. Salinity induced ultrastructural damages in leaf such as swelling of thylakoids, disintegration of grana stacking and intergranal lamellae and destruction of mitochondria (deficiency of cristae, swelling and vacuolation). Such damages were largely prevented by pretreatment with glycinebetaine resulting in greening of the plants. In roots, the epidermis, cortex and root cap were more sensitive to salt stress than the meristem and stele. The most frequently observed ultrastructural alteration due to NaCl salinity was the formation of many large vacuoles in the root tip and root cap cells. The number of mitochondria was increased and they were aggregated in the cytoplasm of the root tip and root cap cells by treatment with NaCl or NaCl plus glycinebetaine. Glycinebetaine could not prevent the NaCl-induced ultrastructural damages in root cells. The effects of glycinebetaine to mitigate the ultrastructural damages in the chloroplast and mitochondria induced by NaCl might be due to the production of many vacuoles in root cells which may act to store Na and decrease its accumulation in the shoot.     

Screening and quantification of an antiseptic alkylamide, spilanthol from in vitro cell and tissue cultures of Spilanthes acmella Murr.

The study revealed, for the first time, accumulation of spilanthol, an antiseptic alkylamide, in in vitro cultures of Spilanthes acmella Murr., a medicinal plant of immense commercial value. To achieve this, in vitro shoots were regenerated via direct organogenesis from leaf-disc explants of Spilanthes. Shoots were induced in the presence of N⁶-benzylaminopurine (BAP) alone or in combination with either α-naphthalene acetic acid (NAA) or Indole-3-acetic acid (IAA) in Murashige and Skoog medium. The best treatment for shoot regeneration was MS + BAP (5.0 μM) + IAA (5.0 μM), which promoted adventitious shoot proliferation in >82% cultures with an average of 5.3 shoots per explant. Regenerated shoots rooted spontaneously with a frequency of 100% on half strength MS medium (major salts reduced to half strength) containing 50 g l⁻¹ sucrose. The plantlets were acclimatized successfully with 90% survival rate. Additionally, ploidy stability of the regenerated plants was assessed by flow cytometry which showed that all investigated plants had the similar ploidy as that of the mother plant. For spilanthol identification, peaks eluted from HPLC were analyzed by mass spectrometry with its characteristic fragmentation pattern. For quantification studies, calibration curve was generated, which revealed a higher amount of spilanthol content (3294.36 ± 12.4 μg/g DW) in the leaves of in vitro plants compare to those of in vivo plants (2703.66 ± 9.6 μg/g DW of spilanthol). An efficient multiplication frequency, ploidy stability and enhanced spilanthol accumulation ensure the efficacy of the protocol developed for this industrially important medicinal plant.     

Effect of lowering the root/shoot ratio by pruning roots on water use efficiency and grain yield of winter wheat

A pot and a field experiment were conducted to assess the effects of root/shoot ratio (R/S) on the water use efficiency (WUE) and grain yield of winter wheat. The R/S was regulated by pruning the roots during the stem elongation stage, resulting in reduced root systems of the plants. At the heading stage, the root dry weight of root-pruned plants was less than that of intact-root plants, but their R/S was similar to that of intact-root plants under both experimental conditions. After tiller pruning, the R/S of root-pruned plants was significantly lower than that of intact-root plants (p < 0.05). Root pruning reduced the rate of leaf transpiration and lowered the number of tillers per plant (p < 0.05) during the vegetative stage. As a result, root-pruned wheat showed reduced water use when compared to intact-root plants before heading (p < 0.05). At anthesis, there was no significant difference in transpiration between plants with intact roots and those with pruned roots in the pots. However, under field conditions, transpiration of root-pruned plants was significantly higher than that of intact-root plants at anthesis. Additionally, at anthesis root-pruned plants had a higher rate of leaf photosynthesis and lower rate of root respiration, which resulted in a significantly higher grain yield at maturity when compared to plants with intact roots. Under both experimental conditions, there were no significant differences in shoot dry weight per plant between root-pruned and intact-root plants grown in monoculture. When root-pruned plants were grown with intact-root plants, the root-pruned wheat was less productive and had a lower relative shoot dry weight (0.78 and 0.86, respectively) than the intact-root plants (1.24 and 1.16, respectively). These results suggest that plants with pruned roots had a lower ability to compete and to acquire and use the same resources in the mixture when compared with intact-root plants. Root pruning improved the WUE of winter wheat under both experimental conditions. This suggests that appropriate management for the root system/tillers in wheat crops can be used to increase grain yield and water use efficiency. Specifically, lowering the R/S improved the grain yield and WUE of winter wheat significantly by lowering its competitive ability and improving root efficiency. Therefore, drought-resistance breeding to improve the grain yield and WUE, at least for wheat, should be made by targeted selection of less competitive progeny with a small R/S for cultivation in arid and semiarid areas.     

Change in Hydraulic Resistance and Shoot Morphology of Napiergrass (Pennisetum purpureum Schumach.) under Shaded Condition

Abstract

Acclimation to light condition is associated with change in water transport system in napiergrass. In this study, the effects of shading on shoot hydraulic resistance and morphology of napiergrass (Pennisetum purpureum Schumach.) were investigated. In the plants under shading (to 30% of full sunlight) for 30 days (S plants), total hydraulic resistance of a shoot (Rshoot) increased from that of full sunlight (control). In the plants grown under shade condition for 24 d followed by full sunlight conditions for 6 d (SF), the Rshoot value was intermediate between that of control and S plants. A similar response to shading was found in total hydraulic resistance of a stem (R_stem), which accounted for more than 60% of Rshoot, but the total hydraulic resistance of the leaves was not significantly affected by shading. Leaf length, leaf area and stem length were larger, but the stem cross-sectional area (SA) was smaller in S and SF plants than in the control plants. SF plants showed similar leaf length, leaf area and stem length to those in S plants, but the SA in SF plants was slightly larger. Normalization of R_stem by SA and stem length decreased the difference among the treatments, indicating the increase of Rshoot and R_stem under shading resulted from the decrease of SA and the increase of stem length.     

Enhanced production of dihaploid lines via anther culture of tetraploid potato (Solanum tuberosum L. ssp.tuberosum) clones

A total of 1000 anther-derived plants was regenerated from tetraploid potato (Solanum tuberosum L.) genotypes. Capacity to undergo androgenesis was analysed in 41 potato cultivars and 7 clones grown either in the greenhouse or in the field. Of the 48 genotypes, 33 produced embryos and 23 regenerated shoots from embryos. Anther-derived plantlet production was determined in genotypes 86110, Agria, Calgary, Escort, Helios, Idole, JO 0982 JO 1432, Kainuun Musta, Kardal, KE48, Matilda, Nicola, Petra, Pito, Rustica, Stirling, Torridon, Ute, Van Gogh, Vebeca, Vento and White Lady. The highest number of shoots (24 shoots/100 anthers) was obtained from cv. Calgary, when anthers were isolated from field-grown donor plants. Incubating anthers at 28 C, rather than at 20 C or 24 C, enhanced embryo production in four genotypes tested. However, shoot production was improved only in cv. Pito cultured at 28 C. When anthers of cv. Petra were cultured at 28 C for four weeks, followed by reduction of culture temperature to 24 C, a high rate of shoot production was recorded (14 shoots/100 anthers). The ratio between dihaploids and tetraploids varied among the anther-derived plants of the different genotypes. The number of dihaploids was highest in potato clone JO1432 (100%) and in cv. Calgary (93%) and lowest in cvs. Pito (21%) and Torridon (6%).     

Fusarium solani Upregulated Sesquiterpene Synthase Expression,Sesquiterpene Production and Allelopathic Activity in Piper betle L.

Activators of sesquiterpene synthase (STS) gene expression and sesquiterpene production in Piper betle L. were examined using quantitative real time PCR and gas chromatography mass spectrometry methods, and the allelopathic activity of untreated and Fusarium solani-treated betel extracts was tested on seed germination and on the shoot and root growth of Thai rice variety PSL2 (Oryza sativa cv. Phitsanulok 2) and three dominant paddy weeds (Eclipta prostrata, Echinochloa crus-galli and Chloris barbata). The results demonstrated that F. solani dramatically upregulated STS expression and productions of β-cubebene, β-caryophyllene and germacrene D sesquiterpene when compared with the untreated control, and that betel extracts had a greater inhibitory effect on weeds than on rice. The effects were more clearly detected on seed germination and root growth than on shoot growth, and they were found to be dose-dependent. It is also noted that F. solani-treated extract had stronger effects than the untreated extract. The species most sensitive to the allelopathic effects was C. barbata, germination of which was completely inhibited even at a dose of 0.1 mg/mL untreated extract. With regards to rice, although betel extract at 1.0 mg/mL showed no inhibition on germination, it affected the elongation of rice roots, in addition to those of the tested weeds. The obtained data suggested that F. solani has potential as an activator of sesquiterpene allelochemical production via STS expression, the latter leading to the treated betel extract having a stronger phytotoxic effect. These results were beneficial in the promotion of natural herbicide production using biotechnology.     

Sprouted Sorghum Extract Elicits Coleoptile Emergence,Enhances Shoot and Root Acclimatization,and Maintains Genetic Fidelity in indica Rice

The high growth-stimulating effect of plant extract has urged the plant biotechnologists to use natural supplements in the culture media instead of synthetic phytohormones. We advocated the effect of sprouted sorghum extract(SSE) on emergence, in vitro acclimatization, and genetic fidelity in coleoptile derived callus of indica rice variety ADT36. The use of SSE with Murashige Skoog medium efficiently acclimatized the root and shoot apical systems. A higher mat and seminal roots(3.4 g biomass) with an efficient shoot primordium elongation were observed with an increase in the concentration of SSE. Seeds treated with SSE medium showed higher germination and earlier coleoptile maturation about 48 h compared to untreated seeds, and there was a higher expression of e EF-1α with an increase in coleoptile length. B5 medium was effective on inducing embryogenic and nodular callus from 3-day-old coleoptile with 3.0 mg/L 2,4-dichlorophenoxyacetic acid and further proliferated effectively with 0.8 mg/L kinetin with a fresh weight of 180 mg. Highly significant regeneration was observed with combination of 2.5 mg/L 6-benzylamino purine and 3.0 mg/L α-naphthaleneacetic acid. The metabolic and genetic profiles of in vitro and directly cultivated plants were the same, examined through Fourier-transform infrared spectroscopy, random amplified polymorphic DNA(RAPD), inter-simple sequence repeat(ISSR) and R-ISSR(combination of RAPD and ISSR) markers, respectively, and thus confirming the significant efficacy of the SSE incorporated medium. Disarmed T-DNA was transformed to coleoptile derived callus through Agrobacterium tumefaciens LBA4404 and confirmed by GUS assay. The T-DNA integration was confirmed by DNA blot analysis using DNA from transient GUS-expressed explants. Thus, SSE can be used as a natural and organic supplement for organogenesis and efficient acclimatizations of shoot and root apical meristems in regenerated plants.     

Identification of QTLs for Cadmium Tolerance During Seedling Stage and Validation of qCDSL1 in Rice

Cadmium(Cd)is a non-essential toxic metal that is harmful to plants.To investigate the genetic mechanism of Cd tolerance in rice,quantitative trait loci(QTLs)associated with Cd tolerance at the seedling stage were analyzed using a recombinant inbred line(RIL)population derived from a cross between PA64s and 93-11.A total of 36 QTLs associated with shoot length,root length,shoot dry weight,root dry weight and total dry weight were detected in Hangzhou and Lingshui of China.Among them,15 QTLs were identified under the control condition and 15 QTLs were identified under the Cd stress condition,and 6 QTLs for Cd tolerant coefficient were detected on chromosomes 1,3,7 and 9.The qCDSL1.1 and qCDSL1.2 were identified in Hangzhou and Lingshui,respectively,and had overlapping intervals on chromosome 1.To further confirm the effects of qCDSL1.1 and qCDSL1.2,we developed a chromosome segment substitution line(CSSL),CSSLqCDSL1,in 93-11 background harboring qCDSL1.1/qCDSL1.2 from PA64s.Compared to 93-11,CSSLqCDSL1 had increased shoot length under the Cd stress condition.These results pave the way for further isolation of those genes controlling Cd tolerance in rice and marker-assistant selection of rice elite varieties with Cd tolerance.     

Tolerance to Fusarium wilt and anthracnose diseases and changes of antioxidative activity in mycorrhizal cyclamen

Mycorrhizal associations imply a remarkable reprogramming of functions in both plant and fungal symbionts. This consequent alteration on plant physiology has a clear impact on the plant responses to biotic stress management. As a consequence, a pot experiment was conducted to study the interactions between the arbuscular mycorrhizal fungus (AMF) Glomus fasciculatum and the two pathogens Fusarium oxysporum and Colletotrichum gloeosporioides and subsequent effect on growth, disease tolerance and the changes in antioxidative ability in cyclamen plants under growth chamber condition were investigated. At plant maturity, inoculation with F. oxysporum and C. gloeosporioides, responsible for Fusarium wilt and anthracnose of cyclamen respectively, significantly reduced shoot and root dry weights, increased both the disease incidence percentage and showed lower antioxidative activity viz. superoxide dismutase (SOD), ascorbate peroxidase (APX), ascorbic acid (AA) and polyphenol contents in plants. In contrast, the growth response and biomass production of cyclamen plants inoculated with AMF was significantly higher than the nonmycorrhizal control plants, both in the presence and absence of the pathogens. Mycorrhization enhanced plants to reduce the Fusarium wilt and anthracnose incidence compared to nonmycorrhizal controls. In every case, without and with pathogen association, plants inoculated with AMF increased the antioxidant (SOD, APX, AA and polyphenol) production compared to control plants. The results demonstrate that AMF have the ability to induce resistance against Fusarium wilt and anthracnose in cyclamen by increasing the antioxidative activity in plants, which promoted plant growth, biomass production and drastically reduced the disease incidence in cyclamen.     

Growth photosynthetic activity and antioxidant responses of mycorrhizal and non-mycorrhizal bajra (Pennisetum glaucum) crop under salinity stress condition

Arbuscular mycorrhizal (AM) fungi alleviating the adverse salt effects on growth was tested in bajra (Pennisetum glaucum). Towards this objective we analyzed the photosynthetic activity, proline, phosphatase activity and various antioxidant enzymes such as peroxidase, catalase and superoxide dismutase at 0, 100, 200 and 300 mM salinity levels in AM inoculated and non inoculated bajra plants. Total chlorophyll content was significantly higher in moderate salinity condition in AM fungus (Glomus fasciculatum) inoculated plants, which lead to increase in growth and nutrient uptake capacity of mycorrhizal plants. Antioxidant activity was either increased or decreased due to responses to different salinity stress conditions. Proline accumulation was induced by salt and it was more in shoot of non-AM inoculated plants, but in roots proline accumulation was higher in AM plants at all levels of salinity. This work suggests that the AM fungus helps bajra plants to perform better under moderate salinity levels by enhancing the antioxidant activity and proline accumulation as compared to non-mycorrhizal plants.     

Alleviation of waterlogging damage in winter rape by application of uniconazole: Effects on morphological characteristics,hormones and photosynthesis

Oilseed rape seedlings (Brassica napus L.) treated with uniconazole were transplanted at the five-leaf stage into specially designed experimental containers, and then exposed to waterlogging for 3 weeks. Pre-treatment of rape seedlings with uniconazole significantly increased seedling height, shoot width, number of green leaves and leaf area per plant, and consequently the shoot, root, and total dry weight after waterlogging. Following waterlogging stress, the uniconazole treated plants had a significantly improved growth including plant height, length and width of leaves, number of green leaves, leaf area per plant, and canopy width at the stem elongation stage, and plant height, stem width, and root, shoot and total dry weight at the flowering stage. At harvest, uniconazole treatment increased the number of primary and secondary branches, seeds per pod, and number of effective pods in branches and in terminal raceme after waterlogging treatment. The uniconazole-induced increase in the number of pods per plant and number of seeds per pod were the two yield components responsible for the significantly greater seed and oil yields obtained from the uniconazole plus waterlogging treated plants, over either the control or waterlogged plants. Uniconazole also reduced waterlogging-induced rise in the erucic acid content of the seeds. The modification of GA₃, zeatin, ABA and ethylene levels due to pre-treatment of rape seedlings with uniconazole might have helped to delay the chlorosis and senescence induced by waterlogging. Uniconazole treatment also increased the leaf photosynthetic rates of waterlogged plants, in part, due to the changes in leaf conductance and hormone levels which ultimately affected various physiological processes.     

Does spatial arrangement of 3D plants affect light transmission and extinction coefficient within maize crops?

Row spacing effects on light interception and extinction coefficient have been inconsistent for maize (Zea mays L.) when calculated with field measurements. To avoid inconsistencies due to variable light conditions and variable leaf canopies, we used a model to describe three-dimensional (3D) shoot structures combined with a model of 3D light transfer. The MODICA model mimics 3D shoot structures of maize plants from digitizations in the field and makes it possible to simulate associated hypothetical canopies by re-arranging plants into different row spacings. All row spacings examined with the model had 10 plants m⁻². By using the light model RIRI, simulations showed the relative importance of development stage and time integration on fraction of light transmitted and on the extinction coefficient. Narrow row spacings consistently had less transmitted light and greater values of extinction coefficient. This modelling tool shows promise to effectively evaluate row spacing to optimize light interception.