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  • Author or Editor: T.T. Muraoka x
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Abstract

Mature almond trees [Prunus dulcis (Mill) D.A. Webb] growing on a very light-textured (Delhi sand) soil were fertilized with 15N-depleted ammonium sulfate during 1980. Although uptake of labeled N from the soil N pool had ceased by 1982, label persisted within the trees at least until 1984. This label presumably represented the residual portion of the organic pool of storage N absorbed by the trees several years before. Leaf, pericarp, and embryo (kernel) samples were collected over a 2-month period during embryo maturation, and samples were processed for mass spectrometric analysis. Total leaf N did not decrease during embryo maturation, but labeled N in leaves decreased by 25%. These data are consistent with the concept of N turnover and flux through mature leaves and transport of N from leaves to fruit. These data indicate also that the N stored overwinter in perennial tissues of almond trees is redistributed within the trees throughout the growing season to support the development and function of annual plant organs such as leaves and fruit.

Open Access
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Abstract

Fruiting branches of French prune (Prunus domestica L.) were exposed to ethylene or the ethylenegenerating (2-chloroethyl)phosphonic acid (ethephon) and subsequently 14C-uptake and ion leakage patterns of excised mesocarp disks were determined. Ion leakage was increased by these treatments, and the magnitudes of variances associated with ethephon-treated samples indicated differences in sensitivity among treated fruit. Under laboratory conditions electrolyte loss was associated with senescence of mesocarp tissue but was not a prerequisite of fruit abscission.

Open Access

Abstract

Non-bearing prune (Prunus domestica L. cv. Agen) trees were fertilized with 15N-KNO3 for 10 days during 9 phenological periods. Nitrate uptake efficienty (NUE) and the distribution of absorbed 15N in the trees were determined for each of these application periods. Nitrate uptake was dependent on presence of leaves, and NUE was low from the period of natural leaf fall until shoot growth had commenced the following spring. NUE increased dramatically during the rapid phase of shoot elongation, and remained high until leaf fall. Nitrogen absorbed from fertilizer was rapidly mobilized by swelling buds and rapidly elongating shoots. The spring flush of vegetative growth utilized both the currently available fertilizer (15N) nitrogen and tree nitrogen reserves. Rapid shoot elongation was primarily dependent, however, on the redistribution of storage N.

Open Access

Abstract

Mature almond trees [Prunuis dulcis (Mill) D.A. Webb] growing on a very light-textured soil (Delhi sand) were “pulsed” in 1980 with a soil application of 15N-depleted ammonium sulfate. Leaching of labeled N from the soil and dilution (with unlabeled N carriers) of residual label in the soil minimized uptake of labeled N from this soil in subsequent years. The percent annual depletion (PAD) of labeled N in tissue samples was 50% and represented the percent annual influx of tree N from the soil N pool. Nitrogen assimilated in previous years also represented 50% of total tree N. The fractional contribution of N absorbed in any prior year, relative to the total pool of storage N, may be expressed as 1/(2)x, where x represents the number of years prior to the current year. The PAD, as measured in tissue samples, was greater in trees growing in the Delhi sand than among comparable trees growing in a heavier-textured soil (Yolo silty clay loam). A hyperbolic depletion function was fitted to the data to predict endpoints of tissue labeling. These endpoints were estimated to be 8.5 and 86.1 years on the light- and heavy-textured soils, respectively.

Open Access

Abortion of distillate flowers (PFA) in a protandrous cultivar of walnut (Juglans regia L. cv. Serr) was increased by N deficiency. Starch and N concentrations in wood of 2-year-old twigs decreased to minimal levels during abortion of distillate flowers. Nitrogen reserves in woody tissues were reduced by foliar N deficiency, as were concentrations of sugars and N in vacuum-extracted xylem sap. Abortive distillate flowers ceased growth before spur leaves reached 50% of full expansion. PFA may result from transient deficiencies of C and N during the spring flush of growth. Depletion of storage C and N was accentuated before maturation of distillate flowers in this cultivar by the metabolic demands of many catkins, spur growth, and leaf expansion.

Free access

Localized and carry-over effects of light exposure [as inferred from specific leaf weight (SLW)] on spur viability, flowering, and fruit set were monitored in selected spurs throughout walnut (Juglans regia, cvs. Serr and Hartley) tree canopies. Shaded spurs (i.e., average SLW <4 mg·cm-2) were predisposed to die during the winter, and spur mortality was accentuated among spurs that had borne fruit that season. More catkins and distillate flowers per spur were characteristic of the more exposed positions within the canopy (as indicated by SLW) during the previous summer and following an “off” year. In exposed `Serr' canopy positions (SLW >5 mg·cm-2), catkin and Pistillate flower maturation was reduced in fruiting spurs by 60% and 30%, respectively, in the subsequent year relative to vegetative spurs. In `Hartley', the number of distillate flowers was also reduced by 35% on spurs that fruited the previous year relative to spurs that had been vegetative. Maximum rates of return bloom and fruit set were evident in spurs exhibiting the highest SLW and N per unit leaf area (NA), specific to each cultivar. Among spurs of both cultivars, distillate flower development was more sensitive to shading in the previous season than was catkin development. Shell weight of `Serr' varied positively with SLW, but kernel weight, fruit N, and oil concentration did not vary “with SLW in either cultivar.

Free access

Experiments were conducted to determine if differential responses of walnut pollen germination to temperature, previously observed to occur among genotypes, were genetically fixed or expressions of phenotypic plasticity representing adaptive responses to temperatures experienced during pollen development. Individual branches of a single walnut (Juglans regia L. cv. Serr) tree were warmed above ambient conditions during the final stages of pollen differentiation by directing a stream of moist, heated air into polyethylene enclosures, each containing an individual branch unit. Pollen was collected at staminate anthesis and incubated in germination medium on a temperature gradient apparatus. Model curves fitted to the in vitro pollen germination data were used to determine optimum germination temperatures. We found adaptive responses of pollen germination to temperatures experienced during pollen development. The optimum temperature for in vitro germination for pollen from branches maintained under ambient conditions was lower than that of pollen from branches with elevated temperature, and optimum germination temperature increased as a log function of integrated daily temperature (degree-days) experienced during pollen development.

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The effects of alternate bearing on recovery and loss of isotonically labeled fertilizer N and B and on the accumulation of carbohydrate and N reserves were assessed in mature `Kerman' pistachio (Pistacia vera L.) trees. Total recovery of labeled fertilizer N applied once (in late January) was ≈ 60% greater if applied to trees entering an “off' than an “on” year, with respect to fruiting. Eleven percent more labeled B was recovered in off- than on-year trees. Five times more N (1 vs. 0.2 kg N) was lost from the tree in fruit and senescent leaflets from on- than off-year trees. In dormant trees, 144% and 22% more starch and N reserves, respectively, were present after off than on years. Thus, on-year trees were characterized by a greater reproductive demand for N and carbohydrates, reduced accumulation of C and N (i.e., storage) reserves in perennial tree parts, and reduced recovery of January-applied labeled fertilizer N than off-year trees. As B is absorbed passively, the higher transpiration that may accompany the 43% larger leaf area per tree and the probability of increased root growth probably contributes to its increased uptake during off years. The enhanced labeled N recovery in early spring by trees entering their off year preceded fruit and seed development in on-year trees. The differential tree capacity for nutrient uptake in spring may have been conditioned the previous rather than the current year. The increased uptake of labeled N by trees entering an off year (i.e., emerging from an on year) was associated with lower levels of carbohydrate and N reserves than for on-year trees that had just completed an off year. Future experimentation should assess the comparative capacity for nutrient uptake by on-and off-year trees at other stages of phenology, e.g., during seed development and postharvest.

Free access

Estimates of leaflet and fruit macronutrient (N, P, K, Ca, and Mg) accumulation and resorption were developed in six (three heavily cropping, on-year and three noncropping, off-year) mature pistachio (Pistacia vera L. `Kerman') trees over three growing seasons during three stages of phenology [the spring growth flush (April to June); seed fill (late June to September); and leaf senescence (September to November)]. Crop load influenced total nutrient content per tree in annual organs (leaves and fruit), the relative allocation of nutrients between leaves and fruit, temporal patterns of nutrient accumulation in annual organs, and the magnitude of net leaf nutrient resorption per tree prior to leaf fall. In off-year trees, macronutrient accumulation in annual organs (leaves) was concentrated during the spring flush of growth. In contrast, significant macronutrient accumulation in annual organs of on-year trees (leaves plus fruit) occurred not only during the spring flush of growth but also during seed fill. Duration and magnitude of macronutrient accumulation were greater in on-year vs. off-year trees. Fruit N and P demand during seed fill was partially met by a net decrease in the N and P contents of the pericarp. These decreases in pericarp nutrient content during seed fill were equivalent to 32% and 26% of embryo accumulation of N and P, respectively. Fruit demand for N, P, and K during the spring flush of “on” years was accompanied by reduced leaf N, P, and K contents per tree. Net leaf N, Ca, and Mg resorption per tree during leaf senescence differed with crop load. Net leaf N resorption was significantly greater in off-year trees than on-year trees. Leaf N resorption presumably represents an important component of the N pool stored in perennial tree parts during dormancy. The greater leaf N resorption following “off” years was a function of greater leaf N concentration and greater leaf biomass per tree. In contrast, net leaf resorption of Ca and Mg was greater in on-year vs. off-year trees. Experimental validation of the magnitude and periodicity of nutrient uptake by mature pistachio trees is needed during the alternate-bearing cycle, especially in light of the potential contribution of current fertilization practices to groundwater contamination.

Free access

Abstract

Mature almond [Prunus dulcis (Mill) D.A. Webb] trees growing on light-(Delhi sand) and heavy-textured (Yolo silty clay loam) soils were fertilized with 15N-depleted ammonium sulfate at different times during the year to permit direct measurement of fertilizer N within the trees. The distribution of fertilizer N between vegetative and reproductive organs was monitored during both the year of application, 1980, and the subsequent year. The later that fertilizer N was applied during the season, the less fertilizer N was recovered in the fruit and leaves that year, and the greater its N contribution to these organs was the following year. Isotopic labeling of fruit and leaves appeared to be relatively unaffected by soil texture during the year of fertilizer application. During the subsequent year, however, the recovery of fertilizer N by fruit and leaves was 2-fold greater on the heavy-textured soil than on the light-textured soil. Recovery of labeled N in fruit was relatively low on both soil types following application of fertilizer during the dormant period. Isotopic N was recovered in fruit in both 1980 and 1981 and constituted about 20% to 28% of fruit N at most. About 25% of the applied N was removed in the fruit on the heavy-textured soil over a 2-year period. Up to 1 kg N per tree was removed annually in the harvested fruit.

Open Access