Biology and life table of Diaeretiella rapae against Brevicoryne brassicae on different cultivars of cauliflower

Phytoparasitica - Diaeretiella rapae (McIntosh) (Hymenoptera: Braconidae) is one of the most promising, effective and a common endoparasitoid of different aphid species including cabbage aphid,...     

Real-time adaptive irrigation scheduling under a limited water supply

The problem of real-time irrigation scheduling under limited water supply is considered. The goal is to develop an irrigation operation policy which maximizes crop yields and is responsive to current season changes in weather and other variables. Because irrigation decisions are sequential and dependent on crop and soil water status, and also because crop yields can only be known at the end of the season, the decisions are arrived at by a two-stage process. In the first or the design stage, irrigations are planned for the entire season at weekly intervals using historical data and an optimal irrigation scheduling model. In the second stage, the decisions for the subsequent weeks are revised each week after updating the status of the system with real time data up to that week and solving the irrigation optimization model once again for the new conditions. Thus, each week an irrigation decision is made, the entire planning horizon is kept in view. The procedure is illustrated by application to a case study.     

Agronomic fortification of rice grains with secondary and micronutrients under differing crop management and soil moisture regimes in the north Indian Plains

Although the System of Rice Intensification (SRI) has been reported to produce higher paddy (Oryza sativa L.) yields with better-quality grains, little research has addressed the latter claim. This study investigated the interactive effects of rice cultivation methods with different irrigation schedules and plant density on the uptake and concentration of sulfur (S), zinc (Zn), iron (Fe), manganese (Mn) and copper (Cu) in the grain and straw of two rice cultivars during two rainy seasons in the northern plains of India. As the two seasons differed in amounts of rainfall, there were impacts of soil moisture differences on nutrient uptake. Plots with SRI cultivation methods enhanced the grain uptake and concentrations of S, Zn, Fe, Mn and Cu by 36, 32, 28, 32 and 63%, respectively, compared to conventional transplanting (CT). Under SRI management, the highest concentrations of S, Zn and Cu in the grain and straw occurred with irrigation intervals scheduled at 3 days after disappearance of ponded water (DADPW; 3_D), whereas Fe and Mn concentrations in the grain and straw were higher with irrigation at 1 DADPW (1 _D ) compared with plots under 3 _D or 5 DADPW (5 _D ). The higher nutrient uptakes were also manifested in higher grain yield in 1 _D and 3 _D plots (by 9 and 6%, respectively) compared with 5 _D . Wider spacing (25 × 25 cm) compared with closer spacing (20 × 20 cm) significantly increased yield and the uptake and concentrations of all the said nutrients in the grains. When comparing the performance of two cultivars, the total uptakes of Zn, Fe, Mn and Cu in both grain and straw were significantly more in Hybrid 6444 than the improved variety Pant Dhan 4. Overall, SRI crop management compared to CT practices led to more biological fortification of rice grains with respect to S and the four micronutrients studied, giving a concomitant yield advantage of about 17% on average in this region.     

Response of American sycamore seedlings to maleic hydrazide and sodium chloride

American sycamore (Platanus occidentals L.) seedlings grown in a hydroponics system were treated with a growth regulator, maleic hydrazide (MH) or sodium chloride, or a combination of the two. Application of maleic hydrazide or sodium chloride retarded plant growth, but combined application did not show significant interaction effects. Treatment with both sodium chloride and MH reduced the dry weight of plant tissue to a greater extent than sodium chloride application alone. Elemental analyses of various plant parts revealed that MH was generally without effect on the level of either sodium or chloride ions. In old stem tissue, however, treatment with MH had no effect in the absence of sodium chloride but was associated with lower chloride content in its presence.     

Condensation nucleus discriminator making optical measurements on fog: a tool for environmental research

An instrument providing a new, rapid, and accurate method of determining the number and critical radii of condensation nuclei with radii under 200 angstroms is described. Based on the principle of the cloud chamber, the instrument measures transient changes in the attenuation and scattering of a monochromatic light beam by the growing fog droplets. From data obtained the absolute number concentration and radii of condensation nuclei can be calculated. Preliminary studies of aerosol formation in beta-irradiated mixtures of air and sulfur dioxide showed that carbon monoxide and methane inhibit the formation of nuclei; relative rate constants can be deduced. Some applications of this instrument for environmental and basic research are pointed out.     

Silencing of host basal defense response-related gene expression increases susceptibility of Nicotiana benthamiana to Clavibacter michiganensis subsp. michiganensis

Clavibacter michiganensis subsp. michiganensis is an actinomycete, causing bacterial wilt and canker disease of tomato (Solanum lycopersicum). We used virus-induced gene silencing (VIGS) to identify genes playing a role in host basal defense response to C. michiganensis subsp. michiganensis infection using Nicotiana benthamiana as a model plant. A preliminary VIGS screen comprising 160 genes from tomato known to be involved in defense-related signaling identified a set of 14 genes whose suppression led to altered host-pathogen interactions. Expression of each of these genes and three additional targets was then suppressed in larger-scale VIGS experiments and the effect of silencing on development of wilt disease symptoms and bacterial growth during an N. benthamiana-C. michiganensis subsp. michiganensis compatible interaction was determined. Disease susceptibility and in planta bacterial population size were enhanced by silencing genes encoding N. benthamiana homologs of ubiquitin activating enzyme, snakin-2, extensin-like protein, divinyl ether synthase, 3-hydroxy-3-methylglutaryl-coenzyme A reductase 2, and Pto-like kinase. The identification of genes having a role in the host basal defense-response to C. michiganensis subsp. michiganensis advances our understanding of the plant responses activated by C. michiganensis subsp. michiganensis and raises possibilities for devising novel and effective molecular strategies to control bacterial canker and wilt in tomato.     

A study of the fate of [14C]maleic hydrazide in white ash and black locust seedlings by high-performance liquid chromatography

The distribution and metabolic fate of [¹⁴C]maleic hydrazide in white ash and black locust seedlings were studied using high-performance liquid chromatography in conjunction with thin-layer chromatography and liquid scintillation spectrometry. Most of the maleic hydrazide was translocated to the leaves and stems of the black locust seedlings within 1 day after treatment but in the case of the white ash seedlings it remained in the stem tissue. After 30 days, the ¹⁴C was concentrated in the leaves of the black locust seedlings, but only in the stem and at the injection point of the white ash seedlings. Approximately 40 and 10% of the applied ¹⁴C was found at the injection points of the white ash and black locust seedlings, respectively. Chromatographic analysis of extracts showed no detectable metabolite in the black locust seedlings but two metabolites were detected in the white ash seedlings.     

Distribution and metabolic fate of [14C]-daminozide injected into silver maple and american sycamore seedlings

The distribution and metabolic fate of [¹⁴C]-daminozide in silver maple and American sycamore seedlings were studied by use of autoradiography, ion-exchange chromatography, thin-layer chromatography (t.l.c.), and liquid scintillation spectrometry. Within one day after treatment with [¹⁴C]-daminozide, radioactivity was detected in all parts of the plant. The ¹⁴C concentrated in meristematic regions of the leaves. Ion-exchange and thin-layer chromatographic analyses of the 50% methanol extracts indicated that no detectable metabolites of daminozide were formed in any of the plant parts but approximately 20% of the applied ¹⁴C, most of it in the stem tissue, was not extractable by aqueous methanol.