dinucleotide dehydrogenase subunit 5 served as an internal positive control for the assays. In addition, BMG tissue was tested for the presence of potyviruses using a universal potyvirus lateral flow assay (Agdia, Elkhart, IN). Plant TNAs were tested by PCR for
Experiments were conducted at Freeville, NY and Riverhead, NY with 0-280 kg/ha of N banded. Tissue samples (both petioles and whole leaves) were taken 5 times starting 32 days from planting. There was a marked increase in yield and specific gravity from the first 112 kg/ha of N and in most cases from an additional 56 kg/ha of N. Both petiole and whole leaf nitrate were sensitive to changes in fertilizer rate that resulted in yield changes. We were encouraged by results obtained with “quick” tests on fresh sap since the pattern paralleled that obtained with traditional lab analysis of dried ground petioles. Although nitrate concentrations did not vary markedly across the varieties used there were substantial differences due to location even when the yield response curve was similar. Rate of N for rate of N, the Freeville samples were substantially higher in nitrate than those from Long Island, except at the 0 N rate, suggesting that the difference is not due to soil residual N.
Abstract
Peroxidase activity measured on leaf disks of vegetable plants is suggested as a rapid tissue test for diagnosing iron deficiency. The reaction is rapid, may be executed under field conditions and apparently corresponds with the metabolically active part of the iron in the leaf tissue.
Abstract
Phosphorus stress caused a general restriction of growth, pinkish tips and purplish leaves and was associated with low tissue P concn. Phosphorus concn for severe deficiency ranged from 0.034 to 0.08%, hidden hunger occurred from 0.09 to 0.11%, and sufficiency 0.12 to 0.27%. Phosphorus removed from the nutrient solutions was recovered in the plants. Soil test P at 50-70 kg/ha did not limit growth.
Nutrient management legislation has prompted an evaluation of alternative nitrogen (N) management techniques. SPAD (Soil Plant Analysis Development) chlorophyll and Cardy nitrate (NO3 -) meters were evaluated for their potential as tissue nitrogen tests in cabbage (Brassica oleracea var. capitata), onions (Allium cepa), and carrots (Daucus carota subsp. sativus). Cabbage, carrots, and onions were grown on both organic and mineral soils in Ontario, Canada in 2000 and 2001. Nitrogen was applied at five rates to cabbage and carrots and three rates to onions ranging from 0 to 200% of current provincial recommended N rates. In an additional treatment, 50% of the recommended rate was applied preplant and sidedress N applications of 40 kg·ha-1 (35.7 lb/acre) were applied when SPAD chlorophyll meter readings fell below 95 (2000) and 97% (2001) of the highest N rate treatment. Yields were generally unaffected by N rate, except in cabbage in 2000, suggesting adequate N was present in most treatments. SPAD chlorophyll meter readings were highly variable among soil types, cultivars, and years. Chlorophyll readings reached a plateau in adequately fertilized crops in many instances. Cardy readings were less variable among soil types, cultivars, and years. The relationship between N rate and sap NO3-N concentration was generally linear. The results suggest that the use of a well-fertilized reference plot is most appropriate for the SPAD meter on these vegetable crops, while the use of region-specific critical NO3-N concentrations was most appropriate for the Cardy NO3-meter. Both meters would be cost advantageous when over 500 samples are tested. The meters were generally easy to use, except for the SPAD meter on carrots. The meters have potential for N management of vegetable crops under Ontario growing conditions.
reduce condensation. There are reports that ventilation has benefited the plant growth in tissue culture systems ( Nowak and Pruski, 2004 ). Due to the limited number of explants and to reduce the workload, we randomly used one medium (McCown) to test if
A multiplicative model of stomatal conductance was developed and tested in two functionally distinct ecotypes of Acer rubrum L. (red maple). The model overcomes the main limitation of the commonly used Ball-Berry model by accounting for stomatal behavior under soil drying conditions. It combined the Ball-Berry model with an integrated expression of abscisic acid-based control mechanisms (gfac). The factor gfac = exp(-β[ABA]L) incorporated the stomatal response to abscisic acid (ABA) concentration in the bulk leaf tissue [ABA]L into the Ball-Berry model by down-regulating the slope and coupled physiological changes at the leaf level with those of the root. The stomatal conductance (gs) down regulation is pertinent in situations where soil drying may modify the delivery of chemical signals to leaf stomates. Model testing results indicated that the multiplicative model was capable of predicting stomatal conductance under wide ranges of soil and atmospheric conditions in a woody perennial. Concordance correlation coefficients (rc) were high (between 0.59 and 0.94) for the tested ecotypes under three different environmental conditions (aerial, distal, and minimal stress). The study supported the use of the gfac factor as a gas exchange function that controlled water stress effects on gs and aided in the prediction of gs responses.
Shoot tip explants from field-grown guava (Psidium guajava L.) trees, which frequently show a high rate of contamination, were cultured on the MS medium with neem leaf (Azadirechta indica L.) extract in H2O. Ten grams of neem powder prepared from crushed dried leaves was made to 200 mL aqueous solution and was left on a laboratory bench for 24 h. The amber-color neem extract was filtered to separate and discard solid. The liquid was refrigerated until needed. To 950 mL basic medium in deionized H2O containing 25 mL macronutrients, 5 mL micronutrients, 5 mL vitamins, 5 mL EDTA + Fe, 2 mL BA, 30 g sucrose, and 7 g agar, 50 mL neem extract was added either before or after autoclaving. No neem extract was added to the control. Medium was adjusted to 5.7 pH. Unused medium was refrigerated. Shoot tips from actively growing young twigs of field-grown L-49 guava trees that showed variable contamination in previous studies were harvested during midmorning hours. Samples were washed in running water and disinfected with 15% Clorox solution with few drops of Tween-20 for 15 min. There were 20 explants in each treatment. Explants were subcultured a week later. None of the four test studies showed contamination-free cultures from field trees. There was no consistency due to autoclaving neem extract. The neem leaf extract did not show complete elimination of contamination, although it delayed it for few days. It was concluded that neem extract was not effective at concentrations used in getting rid of contamination. Therefore, further investigate effect of neem for this purpose higher concentrations need to be examined.
tests are used to monitor the impact of past fertility practices on changes in the soil nutrient status. The recommendations are made based on the results from analytical tests done on soil, plant tissue, and sap, and subsequent crop response. The main
disadvantage of the EL test is that leakage among different tissues is not distinguished ( Calkins and Swanson, 1990 ). The TTC test is based on the principle that living plant tissue can reduce TTC in the mitochondria to produce red formazan, whereas dead