Search Results
Abstract
Roots of 53-day-old pecan seedlings [Carya illinoensis (Wangenh.) C. Koch] were either not flooded or flooded by submerging pots to ≈2 cm above the soil line in containers of water. Leaf gas exchange measurements at 1000 µmol·s–1·m–2 photosynthetic photon flux, 340 µl·liter–1 CO2, and 27°C were made prior to flooding, after 1, 8, or 15 days of flooding, and 7, 14, or 21 days after flooding was terminated. Net CO2 assimilation rate (A) decreased 56% after 1 day of flooding. Flooding 9 or 15 days did not further depress A. Carbon assimilation of trees that had been flooded for 8 days and then returned to nonflooded soil for 7 days were similar to unflooded trees. In contrast, A of seedlings flooded 15 days did not regain the A of unflooded trees 14 days after flooding terminated. Transpiration rates (E) paralleled A in all treatments. Leaf conductance to CO2 (g L ) was positively correlated with A (R2 = 0.94). However, leaf internal CO2 (Ci) concentration was not decreased by reduced gL. Water potential (ψ l ) and turgor potential (ψP) of leaves were higher when trees were flooded, but osmotic potential (ψs) was unaffected.
Abstract
Foliar K applications were evaluated on adult pecan trees [Carya illinoensis (Wangenh.) C. Koch.] in four separate experiments using various rates and timings of either K2SO4 or KNO3. Ammonium nitrate and/or urea also were used to enhance K absorption. Results indicated that foliar K applications using either K2SO4 or KNO3 were not effective in supplying K to the trees. Leaf K concentration, nut size, kernel percent, and yield, in most cases, did not respond to the treatments. Neither NH4NO3 nor urea improved K absorption.
Abstract
Nitrogen and K were applied to 26-year-old ‘Western’ pecan [Carya illinoensis (Wangenh.) C. Koch] trees at 0, 56, 112, or 224 kg ha−1, and 0, 93, or 186 kg ha−1, respectively, for 6 consecutive years (1978–1983). There was a positive relationship between N rate and leaf N concentration and shoot growth. The number of new shoots per 1-year-old shoot was increased by N application. Yield was greater using 56, 112, or 224 kg N ha−1 than no N. Nitrogen rate was negatively related to leaf K concentration and curvilinearly related to leaf Mn concentration, but did not affect leaf Ca or Mg. Leaf P and Zn concentrations were reduced during some years by N application. Potassium application increased leaf K concentration in 1980, 1982, and 1983, but did not affect leaf K concentration in other years. Surface applied K moved to the 30–45 cm depth by 1980 and to the 45–60 cm depth by 1982. Potassium rate was positively related to leaf Mn concentration, but not leaf N, P, Ca, Mg, or Fe concentration. Annual yield was increased by K rate only in 1979, but cumulative yield was positively related to K rate.
Abstract
Vegetative and fruiting shoots were tagged in Oct. 1982 and 1983 on ‘Squirrel’, ‘Stuart’, and ‘Cape Fear’ pecan trees [Carya illinoensis (Wangenh) C. Koch], and flowering was determined the following years. One-year-old shoots were sampled from vegetative and fruiting shoots of each cultivar on 14 Oct. 1982, 9 Feb., 11 Apr., 14 Oct., and 24 Nov. 1983, and 6 Jan. and 17 Apr. 1984 and analyzed for reducing and nonreducing sugars and starch concentrations. Fruiting reduced return bloom of ‘Cape Fear’ in 1983 and 1984, and ‘Stuart’ in 1983. Sugar and starch concentrations varied inversely. Sugar concentrations were increased in November, January, and February, and starch concentrations were greatest during October and April. The total carbohydrate concentration in fruiting shoots of each cultivar was greater or equal to that of vegetative shoots in all but one instance. The degree of return fruiting was positively associated with cultivars with early fruit ripening dates.