Effects of fertilizer application and fire regime on soil microbial biomass carbon and nitrogen,and nitrogen mineralization in an Australian subalpine eucalypt forest

The effects of a range of fertilizer applications and of repeated low-intensity prescribed fires on microbial biomass C and N, and in situ N mineralization were studied in an acid soil under subalpine Eucalyptus pauciflora forest near Canberra, Australia. Fertilizer treatments (N, P, N+P, line + P, sucrose + P), and P in particular, tended to lower biomass N. The fertilizer effects were greatest in spring and smaller in summer and late actumn. Low-intensity prescribed fire lowered biomass N at a soil depth of 0–5 cm with the effect being greater in the most frequently burnt soils. No interactions between fire treatments, season, and depth were significant. Only the lime + P and N+P treatments significantly affected soil microbial biomass C contents. The N+P treatment increased biomass C only at 0–2.5 cm in depth, but the soil depth of entire 0–10 cm had much higher (>doubled) biomass C values in the line + P treatment. Frequent (two or three times a year) burning reduced microbial boomass C, but the reverse was true in soils under forest burn at intervals of 7 years. Soil N mineralization was increased by the addition of N and P (alone or in combination), line + P, and sucrose + P to the soil. The same was true for the ratio of N mineralization to biomass N. Soil N mineralization was retarded by repeated fire treatments, especially the more frequent fire treatment where rates were only about half those measured in unburnt soils. There was no relationship between microbial biomass N (kg N ha^-1) and the field rates of soil N mineralization (kg N ha^-1 month^-1). The results suggest that although soil microbial biomass N represents a distinct pool of N, it is not a useful measure of N turnover.     

Detection of brucella antigen in bovine fetal stomach contents by agar gel precipitation and counter-immunoelectrophoresis

Among 21 fetuses from serologically positive dams soluble brucella antigen was detected in the stomach contents in 14 instances by agar gel precipitation test and in 19 by counterimmunoelectrophoresis. Brucella abortus biotype 3 was isolated from the fetal stomach contents in 15 of these cases. None of 20 fetuses from serologically negative dams revealed brucella antigen in the stomach contents in either test.     

Performance of eucalyptus in the Indian arid zone

Summary The results of adaptability trials carried out on 43 species ofEucalyptus in two different environments viz., Jodhpur and Pali are discussed. It was observed that the species with wide latitudinal distribution and belonging to summer rainfall regions in their native habitat have done well compared to the species with narrow latitudinal distribution and belonging to winter rainfall areas. In general,Eucalyptus melanaphloia, E. terminalis andE. camaldulensis proved to be the most promising species and are recommended for large-scale species elimination trials in the region. However, for the region like Pali having calcareous soils,E. tessellaris should be preferred over other species as it has shown the best performance. The differential growth and development exhibited by different species in the two habitats suggest a need for studying the correct mycorrhizal fungus in the establishment and growth of the species.with 1 fig.     

Role of sucrose synthase and invertases during petal senescence in rose (Rosa hybrida L.)

Summary

The roles of sucrose synthase and invertases were explored in relation to petal senescence in rose (Rosa hybrida L.). A developmental shift in the activities of these enzymes was observed. Higher sucrose synthase activity (0.52 – 0.95 µmol sucrose min^–1 mg^–1 protein) was observed during the initial stages (S1 and S2) of flower bud development, in contrast to invertases. However, the lower activity (0.56 µmol sucrose min^–1 mg^–1 protein) of sucrose synthase at a later stage (S6) of senescence could help the mobilisation of vacuolar sucrose. The different isoforms of invertase exhibited variable levels of activity. Insoluble acid invertases (IAI) were the most active (11.01 µmol glucose min^–1 mg^–1 protein), followed by soluble acid invertases (SAI; 8.02 µmol glucose min^–1 mg^–1 protein), and soluble neutral invertases (SNI; 0.74 µmol glucose min^–1 mg^–1 protein) at Stage-4. A significant decline in invertase activities (IAI, 0.98; SAI, 1.25; SNI, 0.32 µmol glucose min^–1 mg^–1 protein) coincided with higher levels of ethylene production at the later stages (S5 and S6) of flower bud development and senescence. We propose that developmental as well as ethylene-mediated pathways account for petal senescence in rose.     

Microbial and chemical sources of phosphorus supply modulate the yield and chemical composition of essential oil of rose-scented geranium (Pelargonium species) in sodic soils

Rose-scented geranium (Pelargonium sp.) is a highly valued aromatic crop. Its growth is limited by soil salinity and sodicity stress. Arbuscular mycorrhizal (AM) fungus, phosphate-solubilizing bacteria (PSB), and P fertilizers may enhance the growth and secondary metabolism in geranium plants. In this context, a pot experiment was conducted to study the effects of PSB, AM fungi (Glomus intraradices), and P fertilizer on the yield, chemical composition of essential oil, and mineral element acquisition of geranium. The dry matter yield of shoot and essential oil yield, and mineral element (P, K, Ca, Mg, Na, Fe, Cu, and Zn) uptake in shoot tissues of geranium were significantly increased by the inoculation with AM fungi, co-inoculation with AM fungi and PSB, and P fertilization as compared to control. While the co-inoculation of geranium with AM fungi and PSB significantly enhanced the content of the monoterpenes such as citronellol, geraniol, geranial, and a sesquiterpene (10-epi-γ eudesmol), the P fertilization only enhanced the content of a sesquiterpene, 10-epi-γ eudesmol in the volatile oil. We conclude that the co-inoculation of PSB and AM fungi could be the best natural alternative to phosphate fertilizers to enhance the yield and quality of essential oil from geranium plants grown in sodic soils.     

Agrobacterium × plant factors influencing transformation of ‘Joseph's coat’ (Amaranthus tricolor L.)

A protocol is developed for Agrobacterium-mediated genetic transformation of Amaranthus tricolor via explant co-cultivation with Agrobacterium rhizogenes. Bacteria-plant specific factors which influenced transformation were optimized. Of the two Agrobacterium strains employed, LBA9402 was more infectious compared to A4. Bacterial suspensions grown overnight with 100 μM acetosyringone and experiencing O.D.₆₆₀ = 0.6 followed by dilution to a density of 10⁹ cells ml⁻¹ were the most effective. Explants from garden-grown plants were more responsive than those from in vitro cultures; stem internodes being better than leaves. Immersion of the pre-pricked explants in bacterial suspension resulted in a markedly higher transformation frequency compared to the direct injection method. The infection of internode explants with the LBA9402 strain followed by co-cultivation on growth regulator-free MS medium (MS0) for 5 days resulted in emergence of hairy roots up to a maximum frequency of 97.22%. Roots were individually cultured in MS0, but fortified with bactericidal antibiotic (500 μg ml⁻¹ cefotaxime). Rhizoclones showing prolific growth were renewed through successive subcultures in MS0. Opine gene expression was revealed by positive agropine and mannopine synthesis in all selected transformed rhizoclones. Shoot regeneration from root clones, capable of auxin-independent growth and opine proficiency, was stimulated in MS augmented with 2.0 mg l⁻¹ zeatin. pRi TL–DNA rolB and pRi TR–DNA man2 ORF were detected in leaf tissues of regenerated plants from selected hairy root clones through PCR amplification. The implication of such findings is discussed on the possibility of conferring protection to crop amaranths against biotic stress challenges, particularly due to insects, viruses or fungal pathogens.     

Performance of soilless cucumbers in relation to differential fertigation under naturally ventilated greenhouse conditions

A study was carried out in a split plot design in three replicates during 2016–17 to monitor the performance of soilless cucumbers in relation to differential fertigation. The treatments included fertigation levels viz. 100.0% (F1), 85.0% (F2) and 70.0% (F3) in main plots and varieties viz. Kafka (V1), Multistar (V2) and PBRK-4 (V3) in sub plots. Fertigation levels and varieties significantly affected the fruit yield being highest and lowest values for F1V2 and F3V3, respectively. The average fruit yield with and without fruit thinning was obtained in the range of 2.4–3.5?kg plant^?1 and 3.3–4.4?kg plant^?1, respectively. The crop water use efficiency (CWUE) was computed to be in the range of 60.4–86.3?kg m^?3 and 84.6–108.9?kg m^?3 with and without fruit thinning. Overall, the soilless cucumber cultivation in relation to differential fertigation under naturally ventilated greenhouse conditions proved to be a success in terms of plant growth, yield, quality and economic viability.     

Haemoglobin and Albumin Polymorphisms in Indian Water Buffaloes

A total of 507 samples from the Murrah breed of Indian water buffalo were examined for haemoglobin and albumin polymorphism using starch gel electrophoresis. The majority of samples showed the same two band haemoglobin phenotype, A₁A₂, where the fastest band A₁ was about 67 % of total haemoglobin. Two rare phenotypic haemoglobin variants were observed. The one, found in four animals, had three bands and is explained by mutation in the β chain. The other, found in two animals, showed another relationship between the A₁ and A₂ bands than the common type and is assumed to be caused through heterozygosity at a modulating locus. Three albumin phenotypes were observed. Family data were in agreement with these being controlled by two codominant alleles, called Al^F and Al^s. Frequency of Al^F was 0.09 and 0.29 in two different populations. Age and sex did not have any effect on distribution of albumin phenotypes.