Nitrogen fertigation of greenhouse-grown cucumber

Summary This greenhouse study investigated the response of trickle-irrigated cucumber (Cucumis sativa cv. ‘Petita’) to three N levels applied with every irrigation via the irrigation stream. The plants were grown in pots filled with 12 kg of soil. Water containing 5.8, 11.8, or 17.8 mmol N/l, and uniformly supplied with 2.0 and 3.9 mmol/l of P and K, respectively, was applied two to three times daily. In all treatments of 0.3 leaching fraction was allowed. The resulting total N applications were 15.7, 31., and 47.2 g N/plant. The total amount of water applied was 1851/plant. Total N and NO₃-N, in lajinae and petioles, increased with increasing N level whereas P and K in generated decreased. Although different NO₃/NH₄ ratios in the treatments may have influeced the response to N, it could be concluded that the highest yield was obtained with 11.8 mmol N/1 due to increased number of fruit. In the root volume of this treatment the NO₃-N concentration in the soil solution was aroun 7 mmol/1 for most of the growing season. The dry matter concentration of fruits was not affected by the N levels. It was concluded that 11.8 mmol N/1 applied with every irrigation via the irrigation stream is adequate to cover the needs of greenhous-grown cucumber for higher yield (9.42 kg/plant over a harvesting period of 93 days).     

Passive irrigation and functional morphology of crustacean burrows in a tropical mangrove swamp

Flushing measurements and a resin cast of a burrow inhabited by Sesarma messa and Alpheus cf macklay were taken from a Rhizophoraspp. forest. The burrow had 9 openings and occupied a swamp surface area of 0.64 m². Passive irrigation of the burrow was investigated by recording change in conductivity of burrow water in a chamber 45 cm below the swamp surface during tidal inundation of the swamp. The chamber was completely flushed within approximately one hour, i.e. by a single tidal event. Burrow morphology was determined by means of resin casting. The investigated burrow was of discrete structure, with an overall depth of 1.2 m and a total volume of 68 l, i.e. ca. 9% of the volume of swamp soil. The below ground surface area of chambers and tunnels was 3.8 m². The mean and maximum chamber/tunnel diameter was 7 cm and 11 cm respectively. The soil in the close vicinity of the burrow was extensively penetrated by roots, and any two parts of the burrow were located no further than 20 cm away from each other. By reducing diffusion distances within the soil and by being well flushed, the burrows provide an efficient mechanism for removal of excess salt accumulated in the soil around mangrove roots due to exclusion.     

Measurement of 7-dehydrocholesterol and cholesterol in hair can be used in the diagnosis of Smith-Lemli-Opitz syndrome

7-dehydrocholesterol (7-DHC) and cholesterol (CHOL) are biomarkers of Smith-Lemli-Opitz Syndrome (SLOS), a congenital autosomal recessive disorder characterized by elevated 7-DHC level in patients. Hair samples have been shown to have great diagnostic and research value, which has long been neglected in the SLOS field. In this study, we sought to investigate the feasibility of using hair for SLOS diagnosis. In the presence of antioxidants (2,6-ditert-butyl-4-methylphenol and triphenylphosphine), hair samples were completely pulverized and extracted by micro-pulverized extraction in alkaline solution or in n-hexane. After microwave-assisted derivatization with N,O-Bis(trimethylsilyl)trifluoroacetamide, the analytes were measured by GC-MS. We found that the limits of determination for 7-DHC and CHOL were 10 ng/mg and 8 ng/mg, respectively. In addition, good linearity was obtained in the range of 50–4000 ng/mg and 30–6000 ng/mg for 7-DHC and CHOL, respectively, which fully meets the requirement for SLOS diagnosis and related research. Finally, by applying the proposed method to real hair samples collected from 14 healthy infants and two suspected SLOS patients, we confirmed the feasibility of hair analysis as a diagnostic tool for SLOS. In conclusion, we present an optimized and validated analytical method for the simultaneous determination of two SLOS biomarkers using human hair.     

Risk assessment of heavy metal and metalloid toxicity through a contaminated vegetable (Cucurbita maxima) from wastewater irrigated area: A case study for a site-specific risk assessment in Jhang,Pakistan

The present research was conducted in district Jhang, Pakistan, to evaluate the concentration of metals/metalloids in soil and pumpkin (Cucurbita maxima) irrigated with domestic wastewater. Data revealed that the levels of metals and metalloids in soil samples from two different sites were below the safe limits except Cd, whereas, in the vegetable, the concentrations of As, Se, Ni, Mo, Pb, Mn, and Cu were above the safe limits. The levels of 12 metals and metalloids in the soil were ranged between 0.14 to 22.76 mg/kg at site-I and 0.16 to 22.13 mg/kg at site-II. The levels of these metals in the vegetable were found 0.35 to 61.13 mg/kg at site-I and 0.31 to 53.63 mg/kg at site-II. The transfer factor at both sites was highest for As and Co. The pollution load index recorded for Se, Cu, Cd, Mo, Pb, and Co was greater than 1. The daily intake of As, Mn, and Mo was above the oral reference dose, which reflects that the intake of pumpkin is not safe for the inhabitants of the selected sites. The control measures should be taken to phytoextract heavy metals and metalloids from polluted sites so as to reduce the health risks.     

Integration of transhumant pastoralism and irrigated agriculture in semi-arid East Africa

Agricultural development projects in the fertile and most well-watered areas of arid and semiarid Africa usually deny access to nomadic pastoralists whose production system and livelihood depend upon such areas in the dry season and during frequent droughts. The result can be degradation of range resources through overgrazing, and greater vulnerability of pastoralists. Recent calls for compatible land use schemes or nonexclusionary agricultural development projects in the context of pastoralist transhumance, suggest allowing pastoralists structured access to project sites in the dry season in order to utilize forage and water supplies. This paper examines the capacity of an irrigation scheme to support the seasonal influx of transhumant livestock in dry seasons of varying severity. The livestock carrying capacity of the existing mosaic of land use patterns and practices is used in the determination of the proportional areas of land use needed to absorb large seasonal concentrations of livestock.     

Dwarf pea response to gibberellic acid applied to soil through a drip irrigation system,and gibberellic acid biodegradation in soil

Gibberellic acid (29 or 290 M) injected into drip irrigation lines significantly stimulated internode elongation of dwarf peas, and the 290-M soil treatment produced significantly taller plants than did the 29-M treatment. GA₃ uptake may limit GA-induced internode elongation when GA₃ is applied to soil, in contrast to results obtained for hydroponically grown plants, where uptake initially appeared to exceed the rate of hormone metabolism (andersonet al.). It is likely that biodegradation or chemical inactivation limited the plant-availability of GA₃ in the soil. Degradation of moderate GA₃ concentrations in a moist, aerobic loamy fine sand was nearly complete within five days, indicating that the inefficiency of soil applications may outweight the benefits provided by reducing labor costs associated with foliar-spray applications.     

Vegetation patterns on Mount Everest as influenced by monsoon and föhn

The vegetation of Mt Everest is described by means of the dominant plant formations and characteristic features of biotopes. Climatic data givenin connection with weather observations show evidence that the extreme asymmetry of the altitudinal vegetation belt on the south and north slope is induced by heavy rainfall on the south slope and the desiccating effect of the Himalaya föhn in the valleys of the north slope. Biotope shift from hypsozonal distribution on the south slope to extrazonal distribution on the north slope is described, the patterns of the actual timber line are discussed in order to reconstruct the natural upper forest limit, and regressive plant successions during the last 400 years of man's impact are summarized. The dominant vegetation pattern of the alpine belt is compared with that in the European Alps. On the arid north slope alpine steppe communities occur up to 5 500 m. The highest altitudinal vegetation belt and the highest plant communities at 5 960 m are dominated by periglacial processes. The highest records of flowering plants (6 100/6 200 m) and lichens (7 400 m) are discussed in light of the present knowledge on high-altitude vegetation ecology.     

An optimized protocol for the production of high purity maltose

An economical protocol, which is simple, rapid and reproducible for the production of maltose by enzymatic hydrolysis of tapioca starch, has been optimized. The protocol involves liquefaction of 35% (w/w) tapioca starch by bacterial -amylase at 78±2°C to 3 to 5% (w/w) reducing sugars, followed by maximal (85±3% w/w maltose equivalent) saccharification with barley -amylase and pullulanase at 50°C for 24 to 30 h. The post-saccharification recovery protocol comprised decolourization by charcoal, de-dextrinization by denatured spirit precipitation, de-ionization by passage through cation and anion exchangers and dehydration by vacuum drying. A white crystalline maltose powder was obtained with specifications comparable to commercial high purity maltose. The protocol yields at least 60% (w/w) recovery of maltose and is suitable for use by the pharmaceutical industry. The protocol is unique in that it utilizes cheap and easily hydrolysed tapioca starch, leaves no mother liquor, enabling higher recovery of maltose, and allows almost quantitative recovery of limit maltodextrins, a value-added marketable by-product.     

Effect of Meloidogyne incognita and Importance of the Inoculum on the Yield of Eggplant

The relationship between population densities of race 1 of Meloidogyne incognita and yield of eggplant was studied. Microplots were infested with finely chopped nematode-infected pepper roots to give population densities of 0, 0.062, 0.125, 0.25, 0.50, 1, 2, 4, 8, 16, 32, 64, and 128 eggs and juveniles/cm³ soil. Both plant growth and yield were suppressed by the nematode. A tolerance limit of 0.054 eggs and juveniles/cm³ soil and a minimum relative yield of 0.05 at four or more eggs and juveniles/cm³ soil were derived by fitting the data with the equation y = m + (1 - m)z^P⁻T. Maximum nematode reproduction rate was 12,300. Hatch of eggs from egg masses in water or from sodium hypochlorite dissolved egg masses was similar (41% and 39%), but egg viability was significantly greater from egg masses in water (58%) than from sodium hypochlorite dissolved egg masses (12%) after 4 weeks. Greater numbers of nematodes were collected from roots of tomatoes from soil infested with entire egg masses than from tomato roots from soil infested with egg masses dissolved by sodium hypochlorite.