Search Results

You are looking at 1 - 10 of 395 items for :

  • All content x
Clear All
Full access

David Kohanbash, George Kantor, Todd Martin, and Lauren Crawford

5-DC. The two nodes that were developed include the nR5 (Decagon Devices) node, which is capable of controlling 24-V (alternating current) solenoids, and based on user feedback the nR5-DC was developed that can control 12-V (direct current) latching

Free access

Yiwei Jiang, Yaoshen Li, Gang Nie, and Huifen Liu

-Time PCR Detection System using an iTaq™ Universal SYBR ® Green Kit (Bio-Rad), with reaction for 3 min at 95 °C followed by 40 amplification cycles of 10 s at 95 °C and 1 min at 60 °C. Primers for amplification were as follows: for NR , forward 5

Free access

Wilawan Kumpoun, Takashi Nishizawa, Yoshie Motomura, Tanidchaya Puthmee, and Toshiyuki Aikawa

). NR tissue in the non-chilled fruit (non-chilled). The chilled-NR tissue was obtained from the inner portion adjacent to the chilled-D tissue (about 5-mm thickness), and the non-chilled tissue was obtained from the portion equivalent to the chilled-NR

Free access

Raymond A. Cloyd, Amy Dickinson, Richard A. Larson, and Karen A. Marley

experiments in the study. Adult fungus gnats, Bradysia sp. nr. coprophila , obtained from a laboratory colony, were collected in a plastic vial and then placed into the central compartment (A). A small petri dish supporting a 2.5 × 2.5-cm yellow sticky card

Free access

Giuseppe Colla, Carolina María Cardona Suárez, Mariateresa Cardarelli, and Youssef Rouphael

limitations of NO 3 – assimilation is the NR activity ( Stitt, 1999 ; Tischner, 2001 ). In this study, no significant difference among treatments was observed for NR activity at high nitrate conditions (10 m m ), whereas under low nitrate conditions (2.5 m m

Free access

Nathan J. Herrick and Raymond A. Cloyd

the fungus gnat, B. sp. nr. coprophila (Lintner), was maintained in 8.0-L plastic containers with tight-sealing lids that had openings cut into the lids (11.5 × 22.5 cm) with insect screening (0.2 × 0.8 mm Greentek ® ; Edgerton, WI) hot-glued to

Free access

D. Savvas, H.C. Passam, C. Olympios, E. Nasi, E. Moustaka, N. Mantzos, and P. Barouchas

Two successive lettuce crops were grown in spring 2005 in a completely closed hydroponic system. The ratio of ammonium to total nitrogen (Nr) in the fresh nutrient solution (FNS) introduced into the closed system to compensate for plant uptake was 0, 0.1, 0.2 and 0.3 on a molar basis. In all Nr treatments, the concentrations of total N, K, Ca, Mg, P, and micronutrients in the FNS were identical, but that of SO4 2– increased as Nr increased, to compensate electrochemically for the enhanced NH4 + and decreased NO3 supply. The highest fresh and dry weights per plant were attained with the highest ammonium supply (Nr = 0.3) but, even when no NH4 + was included in the FNS as an N source, the plants were healthy without apparent nutritional disorders. The ammonium concentration in the drainage solution dropped to nearly zero in all treatments some days after the initiation of recycling, which implies a preferential uptake of NH4-N over NO3-N. The root zone pH, as indicated by the values measured in the drainage solution, decreased slightly as Nr increased, and ranged from 6.5 to 8.0 in all treatments. The leaf K, Ca, Mg, and Fe concentrations were not influenced, whereas those of P, Mn, Zn, and Cu were enhanced by the increasing NH4 + supply. The increased ammonium supply did not enhance the utilization of N in plant metabolism, although it reduced the nitrate concentration of the internal leaves in the early spring experiment. The leaf micronutrient concentrations were clearly more than critical levels even when NO3 was the sole N source for lettuce, whereas the P concentration approached the lowest critical level when Nr was 0 or 0.1. The stimulation of lettuce growth as Nr was increased to 0.3 may be a consequence of enhanced P uptake resulting from better control of pH in the root zone.

Free access

Rebecca L. Darnell and Gary W. Stutte

Strawberries (Fragaria xananassa Duch. .Osogrande.) were grown hydroponically with three NO3-N concentrations (3.75, 7.5, or 15.0 mM) to determine effects of varying concentration on NO3-N uptake and reduction rates, and to relate these processes to growth and fruit yield. Plants were grown for 32 weeks, and NO3-N uptake and nitrate reductase (NR) activities in roots and shoots were measured during vegetative and reproductive growth. In general, NO3-N uptake rates increased as NO3-N concentration in the hydroponics system increased. Tissue NO3-. concentration also increased as external NO3-N concentration increased, reflecting the differences in uptake rates. There was no effect of external NO3-N concentration on NR activities in leaves or roots during either stage of development. Leaf NR activity averaged ~360 nmol NO2 formed/g fresh weight (FW)/h over both developmental stages, while NR activity in roots was much lower, averaging ~115 nmol NO2 formed/g FW/h. Vegetative organ FW, dry weight (DW), and total fruit yield were unaffected by NO3-N concentration. These data suggest that the inability of strawberry to increase growth and fruit yield in response to increasing NO3-N concentrations is not due to limitations in NO3-N uptake rates, but rather to limitations in NO3 - reduction and/or assimilation in both roots and leaves.

Free access

S. Aquin, Y. Desjardins, and L.-P. Vézina

A study was conducted to determine the implication of nitrate reductase (NR) and glutamine synthetase (GS) during the transition of micropropagated plantlets from heterotrophy to photoautotrophy to document how nitrogen metabolism interfaces with photosynthetic and anaplerotic CO2 fixation. The activity of the two enzymes was determined in different tissues at different organogenic stages during the development of plantlets transferred onto rooting media containing varying quantities of sucrose. Under 3% sucrose, NR activity was much higher in leaves than in crown tissues. When roots are initiating, there is a shift in the proportion of nitrate reduction from leaves to crown. As roots mature, the proportion of nitrate reduction increases in roots. Similar trends were observed under 5% sucrose. In contrast, under 1% sucrose, a higher proportion of the nitrate is reduced in the leaf tissues throughout the culture period. This suggests that nitrate is reduced mainly in leaves in photoautotrophic plantlets, while it is reduced in crowns and root tissues for mixotrophic plantlets. In general, the GS activity follows the pattern of NR, but is always in excess, to enable rapid assimilation of ammonium derived from metabolism and medium absorption.

Free access

Rebecca Darnell

Most Vaccinium species, including V. corymbosum, have strict soil requirements for optimal growth, requiring low pH, high iron, and nitrogen, primarily in the ammonium form. V. arboreum is a wild species adapted to high pH, low iron, nitrate-containing soils. This broader soil adaptation in V. arboreum may be related to increased efficiency of iron or nitrate uptake/assimilation compared with cultivated Vaccinium species. To test this, nitrate and iron uptake, and nitrate reductase (NR) and ferric chelate reductase (FCR) activities were compared in two Vaccinium species, V. arboreum and the cultivated V. corymbosum. Plants were grown hydroponically for 15 weeks in either 1.0 or 5.0 mm NO3 with 0.09 mm Fe. Root FCR activity was greater in V. arboreum compared with V. corymbosum, especially at the lower external nitrate concentration. However, this was not reflected in differences in iron uptake. Nitrate uptake and root NR activity were greater in V. arboreum compared with V. corymbosum. The lower nitrate uptake and assimilation in V. corymbosum was reflected in decreased plant dry weight compared with V. arboreum. V. arboreum appears to be more efficient in acquiring nitrate compared with V. corymbosum, possibly due to increased NR activity, and this may partially explain the wider soil adaptation of V. arboreum.