Chlorophyll “a” fluorescence (Fvar) was compared with respiration and vitamin C content of broccoli [Brassica oleracea L. (Botrytis group)] during storage at 1C. The amplitude of the Fvar maxima declined in a similar manner as respiration and vitamin C content. Fvar was highly correlated with respiration (r = 0·83, P > = 0·0001). The correlation of Fvar with vitamin C content was weaker (r = 0·42, P > = 0·0002). The results demonstrate that Fvar is an indicator of postharvest changes in broccoli and that Fvar can be used as a nondestructive indicator of early changes in tissue condition (i.e., degree of freshness) of broccoli in storage.
G. Préstamo and P. Manzano
The various isozymes of peroxidase of a range of vegetables and kiwifruit were compared using sodium dodecyl sulfate polyacrylamide gel electrophoresis followed by specific activity staining. Peroxidase isozymes were determined in potato (Solanum tuberosum L.), carrot (Daucus carota L.), tomato (Lycopersicon esculentum Mill.), kiwifruit [Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson], cauliflower [Brassica oleracea (Botrytis group)], green beans (Phaseolus vulgaris L.), and horseradish (Armoracia rusticana Gaertn, Mey Scherb.). There was only one isozyme in cauliflower (70 kDa), two in kiwifruit (45-43 kDa), and a range of isozymes (120-36 kDa) in horseradish. Ascorbic acid inhibited peroxidase activity in the extracts.
C.P. Sharma and Sandhya Singh
Cauliflower [Brassica oleracea (Botrytis Group) cv. Pusi] grown in refined sand with 0.01 normal K supply had lower dry matter and tissue concentration of K than the controls and developed visible symptoms characteristic of K deficiency. Compared with control plants, the laminae of K-deficient plants contained significantly higher concentrations of sugars and nonprotein N and significantly lower concentrations of starch and protein N. However, the midribs of K-deficient leaves contained more protein N than leaves of control plants. Substitution of K by Na resulted in increased Na concentrations in leaves and recovery from the K-deficiency effect on the carbohydrate and N fractions. Maximum response to sodium was found in the intercoastal-lamina of K-deficient plants.
Howard F. Harrison, D. Michael Jackson, Anthony P. Keinath, Paul C. Marino, and Thomas Pullaro
Fall transplanted `Commander' broccoli (Brassica oleracea Botrytis group) yield in mulches formed from the residues of killed cowpea (Vigna unquiculata), soybean (Glycine max), and velvetbean (Mucuna pruriens) cover crops was compared to yield in conventional production on bare soil. Average aboveground biomass production was 6.9, 7.7, and 5.9 t·ha-1 (3.08, 3.43, and 2.63 tons/acre) and total nitrogen content of the aboveground tissues was 2.9%, 2.8%, and 2.7% of the dry weight for cowpea, soybean, and velvetbean, respectively. Within each cover crop mulch main plot, subplots received different nitrogen rates, [0, 84.1, or 168.1 kg·ha-1 (0, 75, or 150 lb/acre)]. For several nitrogen level × year comparisons, broccoli grown in mulched plots yielded higher than broccoli grown on bare soil plots. Cowpea and soybean mulches promoted broccoli growth more than velvetbean mulch. The mulches of all three species persisted through the growing season and suppressed annual weeds.
K.M. Batal, D.M. Granberry, and B.G. Mullinix Jr.
The effects of three rates of N, Mg, and B on cauliflower (Brassica oleracea, Botrytis group) yield, average curd mass, and hollow stem disorder were evaluated on sandy and clay loam soils. Cultivars White Empress and Stovepipe were tested on the sandy loam soil and `White Empress' was tested on the clay loam soil. Maximum mean curd mass and maximum yields were obtained with the highest N rates (269 and 381 kg·ha-1) applied to sandy loam and clay loam soils, respectively. Yield response to increased N rates varied with cultivar. Increasing Mg from 22.5 to 90 kg·ha-1 did not affect yield or curd mass on clay loam soil, but increased yield and mean curd mass on sandy loam soil. The Mg effect on curd mass was influenced by N and B rates. On both soil types, the higher Mg and B rates reduced the incidence of hollow stem, but the Mg effect was influenced by N applications. On clay loam soil, increasing B from 2.2 to 8.8 kg·ha-1 reduced hollow stem but had no effect on yield or curd mass. On sandy loam soil, B at 4.4 kg·ha-1 maximized yield and curd mass, but the hollow stem disorder continued to decrease as B rates were increased from 2.2 to 8.8 kg·ha-1.