Fruit Cortex Research Articles

Nitrogen fertilization and elemental composition affects fruit quality of ‘Fuji’ apples

In 1989 to 1995, five rates of nitrogen (N) fertilizer were applied to ‘Fuji’ apple trees grafted on ‘Delicious’ and ‘Granny Smith’ interstems and grown on M.26 rootstock to determine fruit quality and yield. Fruit weight was increased by N fertilizer rate, but fruit production was not influenced appreciably by rate of N fertilizer, for the one year (1994) it was observed. Highest fruit quality was achieved with the lowest N fertilizer rate of 25 lbs.A‐1 (28.4 kg.ha‐1). Fruit quality was negatively related to N in leaves and fruit peel and cortex as well as leaf boron (B), fruit peel copper (Cu), magnesium (Mg) and fruit cortex Mg, and manganese (Mn) for both interstems. Lower rates of N fertilizer were related to lower concentrations of leaf and fruit N, “redder”; fruit skin color, greater fruit firmness and soluble solids concentration, higher fructose levels, and a lower incidence of bitter pit and scald than the higher rates of 100 or 150 lbs N A‐1 (113.6 or 170.5 kg N ha‐1).

The effect of cell turgor on sugar uptake in strawberry fruit cortex tissue

A reduction in cell turgor has been shown to stimulate sugar uptake in several plant sink tissues and it may regulate the import of assimilate into the sink apoplast, as well as maintain cell turgor. To determine whether cell turgor influences sugar uptake by strawberry (Fragaria x ananassa Duch. cv. Brighton) fruit cortex tissue, disks were cut from greenhouse‐grown primary fruit at the green‐white stage of development and placed in buffered incubation solutions containing either mannitol or ethylene glycol as an osmoticum. Cell turgor of fruit disks was calculated from the difference between the water potential of bathing solution and tissue solute potential after incubation at various osmolarities. Cell turgor increased when tissue disks were placed into mannitol incubation solutions more dilute than the water potential of fresh tissue (about 415 mOsmol kg−1). The rate of uptake of [14C]‐sucrose or [14C]‐glucose decreased as osmolarity of the incubation solution increased, i.e. as cell turgor declined. Cell turgor and the rate of [14C]‐sucrose uptake were unaffected when rapidly permeating ethylene glycol was used as an osmoticum. A decrease in cell turgor reduced both the Vmax of the saturable (carrier mediated) kinetic component of sucrose uptake, and the slope of the linear (diffusional) component. The sulfhydryl binding reagent p‐chloromercuibenzenesulfonic acid, an inhibitor of the plasma membrane sucrose carrier, strongly inhibited only the saturable component of sucrose uptake. Increased uptake of the nonmetabolizable sugar, O‐methyl‐glucose, at high turgor was similar to that of glucose, indicating that carrier activity was influenced by cell turgor, not cell metabolism. Turgor did not influence efflux of [14C]‐sucrose from disks and had no effect on cell viability. Strawberry fruit cells do not possess a sugar uptake system that is stimulated by a reduction in turgor.

The effect of cell turgor on sugar uptake in strawberry fruit cortex tissue

The effect of cell turgor on sugar uptake in strawberry fruit cortex tissue

Benzyladenine Affects Cell Division and Cell Size during Apple Fruit Thinning

Benzyladenine (BA), carbaryl (CB), daminozide (DM), and naphthaleneacetic acid (NAA) were applied postbloom as fruitlet thinning agents to mature `Empire' apple (Malus domestica Borkh.) trees. BA, NAA, and CB reduced fruit set and yield per tree, and increased fruit size, percent dry weight, soluble solidscontent and return bloom. Fruit size was reduced, return bloom, length: diameter ratio and flesh firmness were increased, and fruit set and yield unaltered by DM. Although fruit set and yield were similar for BA, NAA, and CB, BA treated fruit were larger, indicating that BA increased fruit size beyond the effect attributable to chemical thinning alone. BA increased the rate of cell layer formation in the fruit cortex, indicating that BA stimulated cortical cell division. NAA, CB and DM had no effect on cell division rate. Mean cortical cell diameter at harvest was increased by NAA and CB and reduced by DM. Cell diameter at harvest in BA-treated fruit was similar to the control. These data support the hypothesis that BA-induced fruit size increase in `Empire' apple results from greater numbers of cells in the fruit cortex, whereas the fruit size increase due to NAA or CB is a consequence of larger cell size. Chemical names used: N-(phenylmethyl)-1H-purine-6-amine [benzyladenine (BA)]; 1-napthaleneacetic acid (NM); 1-naphthalenyl methylcarbamate [carbaryl (CB)]; butanedioic acid mono (2,2dimethyl hydrazide) [daminozide (DM)].

Calcium Sprays and Timing Affect Fruit Calcium Concentrations, Yield, Fruit Weight, and Cork Spot of `Anjou' Pears

Calcium sprays (CaCl2, Mora-Leaf-Ca + Link Ca, or Stopit) increased fruit Ca concentrations and reduced the incidence of cork spot of `Anjou' pears (Pyrus communis L.) during four seasons. All Ca sprays increased yield relative to the control. All sprays resulted in some injury to leaves and fruit, but fruit was acceptable for marketing. At the low rate, Stopit sprays were the least injurious. Early season sprays, in June to July, produced less leaf and fruit injury than late-season sprays, in July to August, or early + late-season sprays. Early or late-season Ca sprays resulted in slightly larger fruit than early + late sprays. Either late or early + late-season sprays led to higher Ca concentrations in fruit cortex than early sprays.

Benzyladenine Effects on Cell Division and Cell Size during Apple Fruit Thinning

Benzyladenine (BA), carbaryl (CB), daminozide (DM), and naphthaleneacetic acid (NAA) were applied postbloom, as fruitlet thinning agents, to mature `Empire' apple trees. Although fruit set and yield were similar for BA, NAA, and CB, BA-treated fruit were larger, indicating BA increased fruit size beyond the effect attributable to thinning. BA applied at 100 mg·liter–1 increased the rate of cell layer formation in the fruit cortex, indicating that BA stimulated cortical cell division. The maximum rate of cell division occurred 10 to 14 days after full bloom (DAFB) when fruit relative growth rate and density reached a maximum and percent dry weight reached a minimum. Cell size in BA-treated fruit was similar to the control. Cell division ended by 35 DAFB in the control and BA-treated fruit when percent dry weight and dry weight began to increase rapidly and fruit density changed from a rapid to a slower rate of decreased density. These data support the hypothesis that BA-induced fruit size increases in `Empire' apple result largely from greater numbers of cells in the fruit cortex, whereas the fruit size increase due to NAA or CB is a consequence of larger cell size.

144 INFLUENCE OF ROOTSTOCKS AND CALCIUM SPRAY RATES, TIMING,AND MATERIALS ON SPRAY INJURY AND FRUIT QUALITY OF `DELICIOUS' APPLES

Sprays of calcium materials were applied at high volume rates (620 g Ca/400 liters) with a handgun during early June, late June, and mid-July versus mid-July, early August, and late August for five years, 1985 to 1989. Leaf injury was most severe for the late sprays but no spray injury was observed on the fruit surfaces. Bitter pit was markedly reduced with all sprays except CaSO4. In some years, bitter pit was controlled better with the early sprays. Either early or late sprays improved fruit quality including overall appearance, reduced scald development, improved red color of the skin, increased fruit firmness and reduced incidence of bitter pit in cold air (0°C) storage. Soluble solids and acidity in the fruit was not affected by calcium sprays. Leaf Ca was higher from the late spray applications than from the earlier applications. All calcium chloride spray materials resulted in increased fruit peel and cortex Ca. Calcium nitrate sprays tended to increase fruit nitrogen concentrations leading to undesirable higher N:Ca ratios in the fruit.

Growth inhibition and impairment of reproductive potential in Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) by commercially available plant extracts

Postembryonic development and adult emergence of Tribolium castaneum (Herbst) were adversely affected in varying degrees when its larval stage was reared on wheat flour treated separately (at concentrations of 0.001–1.0%) with one of the following commercially available extracts: roots of both sweet flag, Acorus calamus Linn. and Java devil pepper, Rauwolfia serpentina Benth ex Kurz, fruit cortex of soap nut, Sapindus trifoliatus Linn. and gum of Indian Myrrh Commiphora mukul Jacq. A marked decline in the reproductive potential, in terms of female fecundity and egg hatchability was observed when the extracts were applied topically or administered orally through diet.

SORBITOL DEHYDROGENASE ACTIVITY AND CULTIVAR-SPECIFIC APPLE FRUIT GROWTH RATES

The activity of sorbitol dehydrogenase (SDH) may be the primary determinant of apple fruit carbohydrate accumulation, perhaps defining cultivar-specific fruit growth rates. During two intervals following June drop, fruit SDH activity of 5 cultivars was assayed along with measurements of fruit relative growth rate (RGR) and total soluble carbohydrate (TSC) and sorbitol levels of fruit cortex tissue. SDH activity varied over 2-fold among cultivars in interval 1 and nearly 7-fold in interval 2. SDH activity was not correlated to fruit RGR or cortex TSC level, but it was negatively correlated to cortex sorbitol level. Defoliation and girdling to restrict sorbitol import slowed fruit growth and reduced SDH activity to nondetectable levels. Growth resumption, presumably following phloem re-establishment in the girdled zone, was accompanied by substantial SDH activity. SDH activity appears to be cultivar-specific and may be influenced by substrate, i.e., sorbitol, availability. While SDH likely plays a key role in apple fruit carbohydrate accumulation, its activity alone may not determine cultivar-specific fruit growth rate.

Sugar-beet seed steep treatments to improve germination under cold, wet conditions

Modifying the present commercial sugar-beet steep treatment (12h in 0.2% thiram suspension, 25°C) to include an initial 2h steep in 0.3M hydrochloric acid, decreased fruit weight and cortex density and improved the performance of the inherently slower part of the population under cold, wet conditions. Adding gibberellins (GA4/7) or an N-substituted phthalimide (AC 94377) to the thiram steep was also beneficial whereas kinetin of N6-benzyladenine gave no improvement. Germination was even more rapid and better synchronised following a 4-day seed advancement sequence, particularly when this started with the acid steep. Overall, it was possible to increase the proportion of seeds which gave a root or produced hypocotyls at least 2cm tall by 9% and 14% respectively; the thermal time needed for the 90th seed to germinate was reduced from 73 to 30 day degrees and synchrony could be improved at least two-fold.

Calcium-mediated Postharvest Changes in Texture and Cell Wall Structure and Composition in `Golden Delicious' Apples

Changes in texture, cell wall structure and composition during storage of Ca-treated and untreated `Golden Delicious' apple fruit (Malus domestics Borkh.) were investigated. The cell wall region of Ca-treated fruit showed no swelling during storage and cell-to-cell contact was maintained, whereas regions of the middle lamella in untreated tissue stained lightly, appeared distended, and eventually separated. In control fruit, microfibril orientation was lost in distended regions of the cell wall, especially in the outer wall region adjacent to the middle lamella. Furthermore, the middle lamella was fenestrated and in some cases was completely degraded. These changes during storage of control fruit were accompanied by a decrease in arabinose and galactose moieties of the cell wall and an increase in soluble pectin. Calcium treatment of fruit inhibited solubilization of polyuronide and arabinose moieties and reduced the loss in galactose content during storage. Tensile strength and firmness were positively correlated to Ca content of the fruit cortex. Excessive tensile stress caused tissue failure in control fruit when cells of the cortical tissue separated at the middle lamella. In contrast, cylinders of Ca-treated fruit fractured through cortical cell walls.

CULTIVAR VARIATION IN APPLE FRUIT GROWTH RATES, SORBITOL ACCUMULATION, AND TISSUE OSMOTIC POTENTIAL

Absolute and relative fruit growth rates (AGR and RGR) of 5 cultivars were calculated from the oven-dry weights of fruits harvested periodically throughout the growing season. Both AGR and RGR were higher for larger fruit of different cultivars with similar days to maturity, and for summer- versus fall-ripening cultivars. Seasonal variability in AGR and RGR was observed, Apple fruit cortex disks were incubated in 14C-sorbitol solutions in vitro to determine if uptake rates at the cellular level varied between cultivars. Rates of sorbitol accumulation, expressed es μg sorbitol per mg dry weight cortex tissue, declined as the season progressed. Within a cuitivar, uptake rates were not relatad to fruit size, nor were differences found between cortex tissue samples from competing fruit on a spur. Sorbitol uptake rates were significantly lower for the more slowly-growing cultivar. The osmotic potential of the expressed cortex sap, sampled on several dates, was consistently lower for the more rapidly-growing cultivar. Thus, inherent differences in fruit growth rates among cultivars may be due to variation in regulation of osmotic potential.

Comparison of the polyphenol profiles of apple fruit cultivars by correspondence analysis

AbstractConcentrations of the major flavonoids and phenolic acids in the peel and cortex of fruit of eight commercial apple cultivars were determined by HPLC. The multivariate statistical technique of correspondence analysis was applied to the polyphenol profiles to describe distinctive groups of cultivars and of polyphenols, and their joint correspondences.Cultural and growing conditions had a limited effect on the polyphenol profiles of the cortex and peel. Chlorogenic acid was the principal polyphenol in the cortex with the lowest levels being in Red Delicious and the highest in Jerseymac, which were compensated by changes in phlorizin. Cortland had low levels of chlorogenic acid and Gravenstein had high levels, but these were offset by the levels of catechins.The quercetin, rhamnoside, was the principal phenolic compound for the peel data with low levels in Red Delicious, Cortland, Spartan and Jerseymac and high levels in Golden Delicious, Gravenstein and Northern Spy. Levels of chlorogenic acid, offset by levels of phlorizin and catechins, distinguished between Red Delicious and Cortland. Rutin was important in distinguishing between Jerseymac and Spartan.

Calcium uptake by developing apple fruits: III. Additional studies on fruit calcium balance

SummaryEarlier papers in this series reported discrepancies between observed rates of Ca uptake by apple fruits and the rates calculated on the basis of a simple mass-flow hypothesis. Results from three further types of experiment designed to investigate these differences are presented. Rates of Ca deposition on filter papers suspended in the orchards were not adequate to explain the greater than expected rate of fruit Ca accumulation early in the season. Analyses of Ca distribution between different tissues of fruiting spurs provided no evidence for remobilization of Ca from the woody tissues of the spur as fruits developed. Different concentrations of CaCl2 were either perfused through stem segments or allowed to equilibrate with samples of fruit cortex at different dates during the season. In each case an apparent equilibrium concentration for the perfusing solution could be determined, at which the concentration of Ca did not change with perfusion. The equilibrium concentration was of the same order a...

Changes in Water Relations and Elastic Properties of Apple Fruit Cells during Growth and Development

Abstract Water relations parameters of individual cells in the cortex of apple fruit (Malus domestica Borkh., ‘Cox's Orange Pippin’) were determined during 2 growing seasons between the end of June and the end of September. Apple and cell diameters doubled during this time. Cell turgor pressure (P) of sliced tissue incubated in a nutrient solution ranged between 6 and 12 bar (0.6 and 1.2 MPa). The elastic cell modulus (∈) increased with both cell turgor and cell volume. For high turgor pressures (P > 5 bar), the average values of ∈ ranged between 30 and 180 bar (3.0 and 18.0 MPa). The half-times (T1/2) for the water exchange of individual cells with their adjacent tissue increased during the seasons from 8–10 s to 20–25 s which was partly due to a decrease of the hydraulic conductivity of the cell membrane (Lp) during ripening. Lp decreased from about 3 to about 1 · 10−6cm · s−1 · bar−1 (from 3 to 1 · 10−7m · s−1 · MPa−1). The probe data allowed estimates of the diffusion coefficient for the propagation of a change in water potential, volume and turgor pressure across the tissue (Dc) · Dc ranged between 3 and 9 · 10−7 cm2 · s−1 (3 and 9 · 10−11m2 · s−1) and increased continuously during the season. The results indicate that the reduction in the elastic extensibility at the cell level (1/∈) does not correspond with the reduction of the firmness of the fruit as maturity is approached. On the contrary, the fruit become softer. Therefore, the physiological meaning of tissue Young's moduli as determined by other methods has to be questioned. The results are discussed with respect to the development of fruit disorders.

Growth of strawberry fruit and sugar uptake of fruit discs at different inflorescence positions

The growth of fruit from greenhouse-grown ‘Brighton’ strawberry plants (Fragaria × ananassa Duch.) was analyzed from anthesis to ripening, Absolute growth rates neared a maximum at the onset of ripening when the rates for primary, secondary, tertiary and quaternary fruit were 106, 53, 22 and 3 mg dry weight day−1, respectively. Length, diameter, fresh weight and dry weight were greatest in primary fruit throughout development, and were progressively smaller in fruit at lower rankings. At 15 days after anthesis, fresh weight of secondary, tertiary and quaternary fruit were, respectively, 55, 13 and 3% of primary fruit weight. The amount and rate of fruit expansion, estimated from achene separation, was highest in primary fruit, the maximum rate being over twice that of secondary fruit. Relative growth rate was also highest in primary fruit from anthesis to red-ripe. To relate fruit growth to rates of sucrose uptake, discs of fruit cortex tissue were incubated in 10 mM 14C-sucrose solutions. The rate of sucrose uptake by tissue discs from primary fruit was greater than uptake by secondary or tertiary fruit tissue and similar to the rate of dry matter accumulation in intact fruit. In primary fruit, sucrose uptake reflected dry matter accumulation at increasing ages, the rate of both activities decreasing 60% from 9 to 17 days after anthesis. Results suggest that sucrose uptake may relate to rates of strawberry fruit growth.

The Ontogeny and Cytogenesis of Cork Spot in ‘York Imperial’ Apple Fruit1

Abstract Histogenetic studies of the young fruit revealed that incipient cork spot in ‘York Imperial’ apples (Malus domestica Borkh.) may appear as early as 3 weeks after fruit set, and that it initially becomes evident as a sporadic gradual necrosis of several parenchymatous cells of the outer cortex. About 1 month later, healthy enlarging cortical cells contiguous to the necrotic region undergo a redifferentiation via direct nuclear or amitotic divisions that result in a promiscuous intracellular proliferation of daughter cells. These remain within the confines of the original mother cell wall until it ruptures. The amitotic nuclei assume a variety of configurations and divide by cleavage. The method by which cell walls form between the intracellular proliferations is undetermined, and there is no evidence of cell plate formation. Once initiated, cork spot proliferation occurs only within the parenchymatous cells of the fruit cortex and is continuous throughout the growing season. There is no evidence of an internal cork cambium per se. Cork spot is not invariably associated with the vascular bundles, and there is no distinct evidence of the senescence of vascular bundles resulting principally from the necrosis. The necrotic condition becomes visible externally as a slightly sunken epidermal discoloration about 3 months after fruit set.

PARTIAL CONTROL OF BITTER PIT IN NORTHERN SPY APPLES WITH A POST-HARVEST DIP IN CALCIUM CHLORIDE SOLUTION

Bitter pit of Northern Spy apples that were stored in air and in controlled atmosphere (CA) storage was decreased by a post-harvest dip in 4% CaCl2 solution containing 0.35% Keltrol. The calcium treatment also decreased breakdown, loss of fruit firmness, and loss of fruit acidity, and increased Ca content of apple cortex tissue. There was no fruit injury. The dip treatment increased rots in one instance, presumably from dispersal of fungal spores during the dipping process and not due to an effect of calcium. Absorption of Ca was slightly greater in CA storage than in air storage. Percent of apples with bitter pit (all treatments combined) was positively correlated with K content of leaf tissue, with Mg and K content of undipped fruit cortex tissue and with (K + Mg)/Ca ratios (eq/eq) of leaf and of undipped fruit cortex tissue. Leaf Ca was significantly related to pit when combined with leaf (K + Mg)/Ca in multiple regressions.

Apple Fruit β-galactosidase and Softening in Storage1

Abstract Fruit softening of apple (Malus domestica Borkh.) and the activity of β-galactosidase in 0.5 m citrate extracts of fruit cortex were compared for ‘Lodi’, ‘McIntosh’, ‘Golden Delicious’, and ‘York Imperial’ during storage at 0° or 3.3°, 10.0°, and 18.3°C. Enzyme activity per g fresh weight increased as fruits softened, but specific activity did not change. Cell wall galactose content also decreased during softening. The decrease in wall galactose was least in ‘Lodi’ which contained the lowest β-galactosidase activity. ‘York Imperial’ which softened most slowly showed the highest β-galactosidase activity at harvest and throughout storage. Concentrated enzyme preparations did not release measurable amounts of reducing sugar, uronic acid, or neutral hexose from isolated cell walls.

Apple Fruit Explant Responses in vitro and Textural Characteristics of the Derived Tissue Cultures1

Abstract Explants of apple (Malus domestica Borkh.) fruit cortex were used to establish tissue cultures of ‘Lodi’, ‘Golden Delicious’, and ‘York Imperial’ harvested at various stages of maturity. Cell division and initial callus formation occurred in all cases and was not affected by fruit age. However, the capacity to produce callus which survived subculture declined in later stages of development, especially for ‘Golden Delicious’. Although somewhat variable, callus of ‘Lodi’ and ‘York Imperial’ was generally soft and that derived from ‘Golden Delicious’ tended to be friable or hard. The texture of the callus was not related to the age of the fruit from which it was obtained. The degree of cell separation in suspension culture was not entirely consistent with the textural characteristics exhibited on solid medium. There was no striking change in the extent of cell separation during development in suspension culture.