Polyphenols were analyzed in expanding buds and developing leaves of pecan [Carya illinoensis (Wangenh.) C. Koch] cultivars with varying responses to Cladosporium caryigenum (Ell. et Lang. Gottwald), the organism causing scab. Plant tissue extracts were examined by high-performance liquid chromatography using a water: methanol gradient to separate polyphenolic components on a C-18 reversed phase column. A diode-array detector was used to identify profile components by retention times and computer matching of ultraviolet spectra to standard compounds in a library. Concentrations of these polyphenols were compared throughout the growing season in leaves of pecan cultivars with low (`Elliott'), intermediate (`Stuart'), and high (`Wichita') susceptibility to scab; during susceptibility to infection by Cladosporium caryigenum from 16 cultivars; and in `Wichita' leaf discs with and without scab lesions. The major polyphenolic constituent of tissues for all cultivars was identified as hydrojuglone glucoside, which was detected in intact buds and leaves throughout the growing season. Hydrojuglone glucoside concentration increased concomitantly with leaf expansion and then declined slowly. Juglone was barely, if at all, detectable, regardless of leaf age. No correlation was found between cultivar susceptibility to pecan scab and the levels of either juglone or hydrojuglone glucoside in the healthy leaves of 16 cultivars. Leaf tissue with scab lesions had significantly higher juglone and hydrojuglone glucoside levels than leaf discs without scab lesions. Chemical names used: 4-8-dihydroxy-1-naphthyl b-d-glucopyranoside (hydrojuglone glucoside); 1,5-hydroxy-naphthoquinone (juglone).
Abstract
Data on 15 traits collected from 30 walnut selections were analyzed for changes in relation to both clone and rootstock age. Data collection began at first flowering (age 3 or 4) and continued annually for up to 28 years on each clone. Significant correlations were found between seasonal timing of the expression of phenological traits and clone age. The general trend was towards earlier leafing, bloom, and time of nut maturity as the clone aged. Correlations with rootstock age were lower than with clone age for phenological traits. Shell and kernel trait expression was more highly correlated with rootstock age than clone age, suggesting that changes may be due to vigor and other effects of grafting rather than aging per se. Estimates of the age of stabilization for phenological traits ranged between 9 and 18 years from germination. It is suggested that changes in leafing, bloom, and nut maturity dates be considered prior to commercial release of walnut cultivars.
Softening and liquefaction of `Solar Set' locules was studied by examining cell wall polysaccharides during fruit developmental stages (FDS) of immature green, mature green and breaker. Ethanol insoluble solids (EIS) were sequentially extracted by H2O, CDTA, and Na2CO3 solutions. The chromatograms of gel filtration among the same-solution extracts of EISs from three FDS were similar. Gradient DEAE also yielded similar patterns among FDS in each extraction solvent, even though the patterns of Na2CO3 extracts differed from those of H2O and CDTA extracts. The mole ratio of total polyuronides decreased for Gal, Ara, and Xyl at later FDS in both EIS and in all extracted polymers. Gal had the highest mole percentage of total neutral sugars, followed by Ara, Xyl, and Rha. While the mole percentage of neutral sugars for Gal, Rha, Ara, and Xyl were relatively similar among FDS in H2O extracts, those in CDTA and Na2CO3 extracts either increased or decreased, depending on individual neutral sugar. SDS-PAGE showed increased density in locule-tissue proteins, especially one with a molecular weight of less than 20 kDa, during later FDS. Results indicate that pectin depolymerization was limited and major neutral sugars commonly composing side chains showed a net decrease.
Abstract
Pomegranate (Punica granatum L. ‘Wonderful’) fruit reached horticultural maturity for commercial harvest when the soluble solids content (SSC) attained a fairly constant level of 15%. The level of titratable acidity (TA) varied from one location to another and from one year to the next but also generally remained stable at the same time that the SSC reached 15%. After harvest, there was no further change in either SSC or TA at 20°C, but redness of the juice continued to increase in intensity up to and after harvest. The respiration pattern of the mature fruit was of the nonclimacteric type, with only traces of ethylene evolved on occasion. Ethylene treatment of the fruit caused a rapid transient rise in CO2 evolution but no changes in SSC, TA, and fruit or juice color. A pseudo-climacteric pattern of respiration was found in very young immature fruit. The respiration rate of dehisced arils paralleled that of the intact fruit, but there was no response to exogenous ethylene treatment. Ethylene evidently stimulated the CO2 output only of the fruit rind.
Two experiments were conducted to develop a protocol for rooting stem cuttings from 3-, 5-, and 7-year-old fraser fir [Abies fraseri (Pursh) Poir.] Christmas trees. The first experiment tested the effect of stumping treatments and tree age on shoot production and subsequent adventitious rooting. One auxin concentration [4 mm indole-3-butyric acid (IBA)] and a nonauxin control were tested. Stock plants were stumped to the first whorl (trees in the field 3 and 5 years) or the first, third, and fifth whorls (trees in the field 7 years). Intact (nonstumped) controls were also included for each age. The second experiment was designed to create a quantitative description of the effects that crown (foliage and above ground branches of a tree) position have on the rooting of stem cuttings collected from stumped and nonstumped trees. The exact position was determined by measuring the distance from the stem, height from the ground, and the degrees from north. Crown positions were recorded as cuttings were collected and then cuttings were tested for rooting response. The rooting traits assessed in both experiments included rooting percentage, percent mortality, number of primary roots, total root length, root symmetry, and root angle. In the first experiment, rooting percentage, primary root production, and total root length increased as the age of the stock plant decreased and the severity of the stumping treatment increased. Auxin treatment significantly increased rooting percentage, root production, root lengths, and root symmetry while decreasing mortality. Overall, the highest rooting percentages (51%) and the greatest number of primary roots (8.1) occurred when 3-year-old stock plants were stumped to the first whorl and treated the cuttings with 4 mm IBA. The greatest total root lengths (335 mm) occurred in cuttings from the 3-year-old stock plants. In the second experiment, rooting percentage was significantly affected by the position from which the cuttings were collected. Cuttings collected lower in the crown and closer to the main stem rooted more frequently than cuttings collected from the outer and upper crown.
Abstract
The muskmelon cultivar Honey Dew (Cucumis melo L.) has unique horticultural and physiological characteristics, most notably an unusually long period between attainment of acceptable horticultural maturity and self-ripening in the field. Patterns of flowering, fruit set, fruit growth, solids accumulation, softening, ethylene production, respiration, and variation among individual fruits were studied during several seasons. Internal ethylene concentration may be estimated by the following formula: ppm internal = 3.7 ± 1.2 × rate of production in µl/kg-hr. The act of harvesting had no effect on ethylene production or internal concentration. Full ripening required an internal ethylene concentration of about 3 ppm. Horticultural maturity was attained at 35 to 37 days after anthesis, but self-ripening required about 47 days. Commercial harvests include fruits in this range of ages, so treatment with ethylene is required for uniform ripening and consumer satisfaction.
A statistical model was used to partition the effects of age group, cutting position within the plant crown, and ramet environment on propagule development from stem cuttings collected from random stock plants of Ilex ×attenuata Ashe `Foster #2' (`Foster' holly). Most of the intra-clonal variation observed originated from sources not partitioned by the model. Small differences in growth were associated with sampling position within the crown. Repropagation gave no indication that factors measured by the model could be passed from ramet to propagule. Within-clone variation was not reduced by repropagation or by hedging propagules to force new growth.
Bell peppers (Capsicum annuum L.) are classified as nonclimacteric fruits while some hot peppers have been reported as climacteric. Responses of peppers to exogenously applied ethylene-releasing compounds suggest ethylene involvement in the ripening process. Ethylene production and respiration rates in 13 cultivars of pepper: `Camelot', `Cherry Bomb', `Chiltepin', `Cubanelle', `Banana Supreme', `Habanero', `Hungarian Wax', `Mesilla', `Mitla', `Savory', `Sure Fire', `Tabasco', and `King Arthur' were studied under greenhouse and field conditions. Fruit from each cultivar were harvested at different maturity stages determined by color, ranging from mature-green to full red-ripe. Carbon dioxide and ethylene production were measured by gas chromatography. Both variables were significantly different among maturity stages for all cultivars. Respiration rates were between 16.5 and 440.3 mg·kg-1·h-1 CO2. Ethylene production ranged from 0.002 to 1.1 μL·kg-1·h-1. Two patterns of CO2 production were identified: higher CO2 production for mature-green fruit with successive decreases for the rest of the maturity stages or lower respiration rates for mature-green fruit with an increase in CO2 production either when fruit were changing color or once fruit were almost totally red. A rise in CO2 production was present for most cultivars. Ethylene evolution increased significantly at maturity or before maturity in all cultivars except `Cubanelle' and `Hungarian Wax'. Respiration rates and ethylene production were significantly different among cultivars at the mature-green and red stages.
Changes in rind firmness and cell wall polysaccharide composition were measured in fruit with a) a soft rind, (`Satsuma' mandarin, Citrus unshiu Marc., cv. Aoshima), and b) a firm rind (hassaku, C. hassaku Hort. ex Tanaka), from August to January of the following year. Rind firmness was similar in both species in August, but hassaku had significantly firmer rind than did mandarin from September to January. Both flavedo and albedo tissues were extracted, and the extracts were hydrolyzed and fractionated to yield four fractions: (hot water, EDTA, hemicellulose, and cellulose). In flavedo tissue, sugar concentration was highest in the cellulose fraction, and lowest in the hemicellulose fraction. The concentration in all fractions decreased as the fruit developed and matured. Although the sugar concentration in the cellulose and EDTA fractions of both species was similar in August, it was significantly higher in both fractions in hassaku than in mandarin in January. The sugar concentration of each fraction from albedo tissue was in the order: cellulose > hemicellulose > hot water > EDTA. The range of variation in cell wall sugars in albedo tissue was smaller than that in flavedo tissue. Chemical name used: ethylenediaminetetraacetic acid (EDTA).
Abstract
The terminology used to describe developmental stages of fruits is often confusing or even misleading. “Mature” and “ripe” are often used synonymously. We find reference to “green” fruit, based on skin or peel color, used interchangeably with “unripe”, the latter without referring to pigmentation but rather to a state of non-palatability. We see in the literature such words used synonymously as “overripe” and “senescent” in describing a fruit in a very late stage of development. Such terms as “early maturity”, “optimum maturity”, or “full maturity” leave some doubt as to what stage is actually under consideration. At best, different authors are not always referring to the same stage, even when dealing with the same fruit.