Scanning electron microscopy studies were made on pollen samples from several small fruit crops: 3 selections of blueberry (Vaccinium), 4 Vitis spp. (V. vinifera L., V. cinerea Engelm., V. rupestris Scheele, and V. amurensis Rupr.), 2 cultivars of raspberry (Rubus), 5 cultivars of blackberry (Rubus), and several species and ploidy levels of strawberry (Fragaria) including 54 cultivars of F. × ananassa Duch., as well as pollen of Duchesnea and Potentilla.
Pollen size and exine characteristics were similar for 4 grape species examined. Polyploid blueberry selections were separable from the diploid selection by pollen grain size. Raspberry and blackberry pollen differed in size, exine ridging or reticulation, and presence of borderless or collared pores. Strawberry pollen is characterized by exine ridging and absence of pores. Cultivars of Fragaria × ananassa could be categorized into 4 groups according to exine ridge patterns. Cultivars exhibited broad longitudinal ridges or were characterized by less prominant to indistinct ridges. One cultivar was unique in that anastomosing ridges were present between adjacent ridges.
Pollen grains of diploid F. vesca L., F. vesca fma. semperflorens Duch., and F. nubicola Lindl, ex Lacaita; a tetraploid clone of F. vesca; the hexaploid F. moschata Duch.; and octoploid F. × ananassa, F. chiloensis (L.) Duch., and F. virginiana Duch. are broadly elliptical, tricolporate and moderately to prominently ridged. Size of pollen and prominance of exine ridges appeared to correspond with ploidy level. Pollen of F. nipponica Mak. differed in that grains are subprolate to sphaeroidal and exine is ornamented with minute, rounded to subconical verrucae arranged in rows. Pollen of the related genera Duchesnea and Potentilla were very similar morphologically to those of octoploid Fragaria spp., except that pollen of D. indica (Andr.) Focke are larger and the exine of P. recta L. exhibits an extremely minute pore structure.
Traditionally, the size control achieved in summer-pruned apple (Malus domestica Borkh.) trees has been attributed to the removal of shoot leaf area before it could replace the storage carbohydrate depleted during its initial growth. Therefore, tissues of young Top Red ‘Delicious’/M 9 trees grown in pots, and mature, field-grown ‘Jonathan’/M 26 trees were summer-pruned and subsequently analyzed for carbohydrate and nutrient element content. Increasing the severity of summer pruning (the length of shoot removed) did not affect the concentration of water-soluble reducing sugars (SRS) or insoluble hydrolyzable carbohydrates (IHC) in the basal shoot section of the Top Red ‘Delicious’/M 9 trees 11 weeks after pruning. Summer pruning 1) increased leaf SRS, N, K, B and stem IHC and 2) decreased leaf Ca and Mg in shoot regrowth. Levels of Fe, Ca, Zn, Al, and Na in the leaves of regrowth were not affected by summer pruning. There was no significant effect of pruning on SRS or IHC levels in the roots. A separation of the carbohydrates by gas chromatography revealed increasing glucose and fructose concentrations in the roots as pruning severity increased, but sorbitol, sucrose, and phloridzin concentrations in roots were not significantly affected. Neither previous season’s summer pruning nor fruit cropping of ‘Jonathan’/M 26 trees affected SRS or IHC of spur shoots in March or June, except that presence of fruit reduced IHC of spur leaves in June. SRS levels in roots in June were reduced by the previous year’s cropping, but not influenced by summer pruning. Root IHC was not influenced by either pruning or cropping treatments. Spur leaf N, Ca, Mg, Mn, and Al were reduced on defruited trees, with K, Ca, Mn, and Al generally being increased by summer pruning. Pruning and cropping treatments generally did not affect levels of P, Fe, B, Cu, Zn, or Na in spur leaves in June; but summer pruning increased K concentration in harvested fruit.
A study was undertaken to determine the seasonal dynamics of leaf and fruit K content and the influence of tree K status and fruit growth on leaf and fruit K accumulation rates in French prune (Prunus domestics L. cv. d'Agen). Mature trees in a commercial orchard were treated with various rates of K2 SO4. (O to ≈20 kg/tree) in the fall. Fruit dry weight yield per tree at harvest and fruit K content were higher for high-K trees, but fruit percent K (by dry weight) was ≈1.0% for all trees. Leaf scorch and subsequent abscission severely reduced the canopy of K-deficient trees. Significant positive linear relationships between leaf and fruit K accumulation rates existed for the periods of 28 Apr.-28 May (May) and 28 May-7 July (June). A significant negative linear relationship existed between these two criteria from 7 July-3 Aug. (July). May (0.237 mg K per fruit-day) and July (0.267 mg K per fruit-day) mean fruit K accumulation rates were similar, but both were significantly higher (P = 0.001) than those for June (0.140 mg K per fruit-day). Mean leaf K accumulation rates for May (- 0.007 mg K per leaf-day) and July (-0.010 mg K per leaf-day) were similar, but both were significantly (P = 0.001) less than for June (0.005 mg K per leaf-day). Potassium per fruit accumulation was highest in trees with highest K status. Periods of net leaf K efflux and influx did not precisely correlate with fruit growth stages measured by fruit dry weight. The period of lowest fruit K accumulation (28 May-7 July) coincided with the period of maximum dry matter accumulation by the kernel. After 7 July, all increases in fruit dry weight and K content were due to mesocarp growth.
The capacity of ‘Washington’ navel orange fruit [Citrus sinensis (L.) Osbeck] to synthesize and catabolize purines and pyrimidines was assessed. De novo biosynthesis of purine nucleotide was demonstrated by [14C] bicarbonate incorporation into purine nucleotides, blockage of this process by four known inhibitors, and assimilation of radiolabeled carbon from formate, both carbons of glycine, and carbon-3 of serine into the adenine ring. De novo synthesis of pyrimidines via the orotate pathway in young fruit was demonstrated by incorporation of [14C] bicarbonate and [6-14C]orotic acid into uridine nucleotides, release of 14CO2 from [7-14C]orotic acid, and blockage of these processes by 6-azauridine. Synthesis of purine and pyrimidine nucleotides via salvage reactions was demonstrated by incorporation of radiolabeled bases and ribonucleosides into nucleotides and into nucleic acids. Release of 14CO2 from radiolabeled adenine, adenosine, hypoxanthine, and xanthine, uric acid, urea (purines), uracil, and uridine (pyrimidines) provided evidence the pathways for catabolism (degradation) of purines and pyrimidines in navel orange fruit are similar to those found in microorganisms and animal tissues. To the best of our knowledge, this report is the first to assess the capacity of anabolic and catabolic pathways of purine and pyrimidine nucleotide metabolism in fruit of any species. De novo synthetic activities in orange fruit permit increases in the pools of purine and pyrimidine nucleotides using simple precursors. Further, the patterns of salvage and catabolism suggest riboside pools are reused predominantly as nucleotides, while the majority of base pools are degraded to permit recycling of carbon and nitrogen into other metabolites.
Four adjacent heavily cropping 12-year-old `Petite d'Agen' prune (Prunus domestica L.) trees were selected, and two of the trees were defruited in late spring (28 May) after the spring growth flush and full leaf expansion. Trees received K daily through the drip-irrigation system, and 15N-depleted (NH4)2SO4 was applied twice between the dates of defruiting and fruit maturation. Trees were excavated at the time of fruit maturity (28 July) and fractionated into their component parts. The following determinations were made after tree excavation and sample processing: tree dry weight, dry weight distribution among the various tree fractions (fruit, leaves, roots, trunk, and branches), tree nutrient contents, within-tree nutrient distribution, total nonstructural carbohydrates (TNCs), and recovery of labeled N. Trees only recovered ≈3% of the isotopically labeled fertilizer N over the 6-week experimental period. Heavily cropping trees absorbed ≈9 g more K per tree (17% of total tree K content) during the 2-month period of stage III fruit growth than defruited trees. The enhanced K uptake in heavily cropping trees was apparently conditioned by the large fruit K demand and occurred despite greatly reduced levels of starch and TNCs relative to defruited trees. Fruit K accumulation in heavily cropping trees was accompanied by K depletion from leaves and perennial tree parts. Except for K, fruited and defruited trees did not differ in nutrient content.
also been important. To date, of the 27 crop species registered in the GE Approval Database of the International Service for the Acquisition of Agri-biotech Applications ( ISAAA, 2015 ), only eight vegetable and fruit crops [i.e., eggplant ( Solanum
In Poland, gooseberry is an important small fruit crop. Plants are grown on commercial plantations as well as in home gardens. In addition, this crop is a good supplement to the cultivation of blackcurrant ( Ribes nigrum ) and redcurrant ( Ribes
for subtropical peach fruit ( Olmstead et al., 2015 ; Predieri et al., 2006 ). The effect of N on TSS and TA has been reported in a number of fruit crops such as grape ( Bavaresco et al., 2001 ), apple ( Nava et al., 2008 ), and tomato ( Simonne et al
1 Associate professor. 2 Visiting scientist. Shaanxi Fruit Crops Research Center, Xi'an, 710061, People's Republic of China. We thank D.R. Parker of University of California, Riverside, for providing Geochem-PC software and guidelines for its use
1 Former Research Assistant. Present address: Fruit Crops Dept., Univ. of Florida, Gainesville, FL 32611. 2 Professor, Dept. of Horticulture. Technical contribution no. 2934 of the South Carolina Agricultural Experiment Station, Clemson Univ. The