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Open access

Patrick J. Breen

Abstract

Peach (Prunus persica Batsch. ‘Lovell’) seedlings and ‘Marianna 2624’ plum (P. cerasifera Ehrh. X P. munsoniana Wight & Hedr.?) cuttings were budded with ‘Fay Elberta’ peach and ‘Marianna 2624’. Of the 4 combinations only ‘Fay Elberta’/‘Marianna 2624’ showed foliar symptoms indicative of graft incompatibility; those trees budded in mid-March appeared abnormal by early August. Prunasin, the only cyanogenic glycoside detected in both species, accumulated in young scion bark of ‘Marianna 2624’ and peach to nearly equal levels. Amounts of prunasin in leaves and bark of ‘Fay Elberta’ on peach were usually greater than in those on plum. The level in the scion bark of ‘Marianna 2624’ was similar on both rootstocks. In late summer, the quantity of the glucoside in peach scion bark rose above that in corresponding plum bark; however, the prunasin concentration in both leaves and scion bark of ‘Fay Elberta’/‘Marianna 2624’ trees was not correlated with the severity of incompatibility symptoms. The prunasin level in the plum rootstock bark immediately below or 18 cm from the union was unaffected by the scion species or by signs of ill-health in the peach top. Although the rootstock was shown capable of affecting the accumulation of prunasin in scion tissues, the stability of the level of this glucoside in the peach/plum combination suggests that cyanogenesis is not closely linked with their incompatibility.

Open access

Kay Ryugo and Patrick J. Breen

Abstract

Treatment of ‘Marianna 2624’ plum cuttings for 7 days with 1-14C-IAA with or without a pretreatment with 4000 ppm indolebutyric acid (IBA) for 5 sec revealed that the synthetic hormone inhibited IAA oxidase activity as measured by the decreased rate of 14CO2 evolution. KOH hydrolysis of different radioactive zones on paper chromatograms derived from alcoholic extractives of cuttings yielded presumptive IAA upon re-chromatography. Likewise, KOH and peptidase treatment of the alcohol insoluble residue yielded a radioactive substance with chromatographic properties characteristic of IAA. The presence of presumptive IAA and ninhydrin-positive substances in the peptidase hydrolyzate indicate that IAA was bound to protein(s). Appreciable radioactivity still remained in the alcohol insoluble residue after protein hydrolysis.

Open access

Cynthia Gilbert and Patrick J. Breen

Abstract

The differential tendency to form misshapen fruit and anther quality and pollen production were determined in ‘Benton’, ‘Totem’, ‘Olympus’, and ‘Tyee’ strawberries (Fragaria × ananassa Duch.) in field trials in 1983 and 1984. All flowers had a full set of anthers; however, the proportion of anthers that appeared unhealthy (dull yellow, brown, or black) varied. Usually the proportion of unhealthy anthers was higher in primary than in secondary or tertiary flowers of an inflorescence. Primary flowers often contained only unhealthy anthers. This condition was found in 90% of the primaries of ‘Benton’ in 1983 and in all those of ‘Tyee’ in both years. ‘Tyee’ released ≤6000 pollen grains per flower. When 75% or more of the flowers at a ranking had at least some healthy anthers, pollen production averaged ≥240,000 grains per flower. ‘Tyee’ had the highest incidence of misshapen fruit (18–19%) in both years. Comparable values were ‘Benton’, 14–17%; ‘Olympus’, 10–11%; and ‘Totem’, 7%. From 42% to 70% of the primary fruit of both ‘Tyee’ and ‘Benton’ were malformed each season. Low pollen production in ‘Tyee’ and ‘Benton’, a result of anther failure, likely contributed to the high incidence of malformation in primary fruit.

Free access

Glen L. Creasy and Patrick J. Breen

A fruit-set disorder of grape, called Inflorescence Necrosis (IN), causes death of flower cluster tissue near bloom. Various chemical treatments have been reported to increase IN severity. Separate studies show that high flower cluster NH4+ is related to naturally occurring IN. We designed a field trial to determine if treatments thought to influence IN severity also affect flower cluster NH4+. One week before first bloom, flower clusters were dipped in solutions of either methionine sulfoximine (MSO, an inhibitor of NH4+ assimilation), α-keto glutarate, (NH4)2HPO4, KNO3, NAA, GA, or an emulsion solution reported to increase transpiration. Also, ethephon was sprayed on whole vines 1 week before first bloom. Flower clusters were collected 5 days after treatment. MSO increased tissue [NH4+] by almost 2-fold over that of controls. NAA and GA reduced [NH4+] a small amount, possibly due to their slightly higher fresh weights. Other dip treatments did not affect [NH4+]. Despite high [NH4+] in MSO treated clusters, there were no visual differences in IN between treatments. Ethephon increased cluster [NH4+] 20% over that of controls, but caused more severe IN. These data show that flower cluster [NH4+] is not always coupled with IN symptoms.

Free access

Kirk W. Pomper and Patrick J. Breen

Expansion of green-white and red fruit in control (watered) and water-stressed greenhouse-grown strawberry (Fragaria ×ananassa Duch. `Brighton') plants was monitored with pressure transducers. Expansion of green-white fruit in control plants was rapid, showing little diurnal variation; whereas in water-stressed plants, fruit expansion occurred only during dark periods and shrinkage during the day. Red fruit were mature and failed to show net expansion. The apoplastic water potential (ψaw), measured with in situ psychrometers in control plants was always higher in leaves than in green-white fruit. In stressed plants, ψaw of leaves was higher than that of green-white fruit only in the dark, corresponding to the period when these fruit expanded. To determine the ability of fruit to osmotically adjust, fruit were removed from control and water-stressed plants, and hydrated for 12 hours; then, solute potential at full turgor (ψs 100) was measured. Water-stressed green-white fruit showed osmotic adjustment with a ψs 100 that was 0.28 MPa lower than that of control fruit. Mature leaves of water-stressed plants showed a similar level of osmotic adjustment, whereas water stress did not have a significant effect on the ψs 100 of red fruit. Fruit also were severed to permit rapid dehydration, and fruit solute potential (ψs) was plotted against relative water content [RWC = (fresh mass - dry mass ÷ fully turgid mass - dry mass) × 100]. Water-stressed, green-white fruit had a lower ψs for a given RWC than control fruit, further confirming the occurrence of osmotic adjustment in the stressed fruit tissue. The lack of a linear relationship between turgor pressure and RWC prevented the calculation of cell elasticity or volumetric elastic modulus. Osmotic adjustment resulted in about a 2.5-fold increase in glucose and sucrose levels in water-stressed green-white fruit. Although green-white fruit on water-stressed plants showed osmotic adjustment, it was not sufficient to maintain fruit expansion during the day.

Free access

Kirk W. Pomper and Patrick J. Breen

Invertase (INV) may influence sugar levels and assimilate transport in strawberry fruit. Several groups, including our own, have only detected acid INV (optimum pH 4.6) in strawberry fruit, however, recently Hubbard et al. (Physiol. Plant. 82:191-196, 1991) reported the presence of a neutral INV (pH 7.5). Since dissimilar isolation protocols may have contributed to the different findings, we re-examined our work with developing `Brighton' strawberry using the extraction procedure of Hubbard et al. Neutral INV activity per gFW (pH 7.5-8.0) increased many fold as fruit developed from green to the red ripe stage. Acid INV activity decreased markedly from green-white to the red stage. In addition, when fruit extracts were precipitated with cold acetone, a pellet contained 60% of the acid INV activity, and a surface coagulation of protein contained 60% of the neutral INV activity. This allowed easy separation of these two enzymes. Extraction methodologies affect isolation of neutral INV activity from strawberry fruit.

Free access

Guiwen W. Cheng and Patrick J. Breen

Fruit size, number of receptacle cells, and mean cell size were determined throughout development of secondary fruit of three day-neutral strawberry (Fragaria ×ananassa Duch.) cultivars grown in a greenhouse. Cells were counted after enzymatic separation of receptacle tissue, and mean cell volume was estimated from cell count and receptacle tissue volume. Size of mature fruit was small (3.8 g) in `Tillikum', medium (11.5 g) in `Tristar', and large (15.6 g) in `Selva'. Fruit size was correlated with the number of achenes per berry. Mature fruit of `Tillikum' had a lower fruit fresh weight per achene and lower achene population density (achenes per square centimeter) than the larger-fruited cultivars. The average number of cells per mature fruit was 0.72 × 106, 1.96 × 106, and 2.94 × 106 for `Tillikum', `Tristar', and `Selva', respectively. The relative difference among cultivars in the number of receptacle cells was established by the time of anthesis. In all cultivars, cell division was exponential for 10 days following anthesis and ceased by the 15th day. Mean cell volume increased slowly during active cell division, but rose rapidly and linearly for 10 days after cell division halted. Mean cell volume of all cultivars increased > 12-fold after anthesis and was ≈ 6 × 106 μm3 in mature fruit. The genotypic variation in the size of mature fruit was not the result of large differences in either duration of cell division after anthesis or mean cell volume, but rather was primarily due to differences in the number of receptacle cells established by anthesis.

Free access

Guiwen W. Cheng and Patrick J. Breen

Studies on regulation of production of phenolics in strawberry (Fragaria X ananassa Duch,) fruit were initiated by monitoring phenylalanine ammonia-lyase (PAL) activity and levels of anthocyanins, flavonoids, tannins, and other soluble phenols throughout fruit ontogeny in `Tillikum'. PAL catalyzes the first step in the biosynthesis of phenylpropanoids, which are further modified into a wide variety of phenolic compounds. Peak in PAL activity (1 mol· s-1 = 1 kat) of 90 pkat· mg-1 protein was detected at 5 and 27 days after anthesis (DAA), when fruit was green and nearly ripe, respectively. PAL activity was only ≈10% of peak values in the white berry stage, when. fruit growth was most rapid. The second peak in PAL activity was followed by a rapid drop, to nearly zero in red-ripe fruit at 30 DAA. Total soluble phenols reached a maximum level soon after anthesis, just before the first peak in PAL activity, then declined to a low constant value well in advance of fruit ripening. Similar changes were observed in levels of tannins and flavonoids that, at anthesis, accounted for 44% and 51% of the soluble phenols, respectively. The concentration of anthocyanin was very low throughout most of fruit development, but beginning at 23 DAA it increased from <0.03 to >0.53 mg·g-1 fresh weight in 3 days. This accumulation paralleled the second rise in PAL activity. Accordingly, strawberry fruit have a developmental-dependent expression of PAL activity and accumulation of phenolic substances derived from the phenylpropanoid pathway.

Open access

Yin-Tung Wang and Patrick J. Breen

Abstract

Buds or open flowers are often removed in the production of Easter lily (Lilium longiflorum Thunb.) bulbs. To determine if time of flower removal affects bulb size or plant growth, flower buds of container-grown ‘Nellie White’ plants were removed when the length of the largest flower bud was 1.0 cm (early) or 3.5 cm (late). Net photosynthesis of the 5th (upper) and 25th (mid-shoot) leaves was monitored and plants were harvested 2 months after full bloom of intact controls. Early disbudding stopped pedicel growth, inhibited stem elongation, and reduced total leaf area 12%, but did not affect bulb weight. Stem elongation was inhibited less by late disbudding; leaf area and plant weight were unaffected. Both fresh and dry bulb weights of late disbudded plants increased by 15%. Early disbudding reduced the rate of net photosynthesis of leaf 5 (particularly during the 3 weeks following full bloom), whereas late disbudding had less effect. Treatments did not affect photosynthesis of leaf 25. Reduced stem growth under late disbudding, without a severe reduction in photosynthesis, may have increased the availability of assimilate for bulb growth. Early disbudding caused 81% of the daughter bulbs to sprout prematurely, compared to 27% for late disbudding and 9% for controls. In a field study, removing flower buds at 1.5 cm or 4.0 cm in length increased bulb fresh weight over intact controls by 12% and 30%, respectively. Disbudding did not increase sprouting of field-grown plants. Delaying removal until the first flower bud is 3.5–4.0 cm long reduces deleterious effects on shoot growth while significantly improving bulb size.

Open access

Patrick J. Breen and Tom Muraoka

Abstract

The top leaf of fresh softwood cuttings of ‘Marianna 2624’ plum (Prunus cerasifera × Prunus munsoniana) was exposed to 14CO2 and the effect of leaf area and indolebutyric acid (IBA) on rooting and distribution of 14c was assessed. IBA enhanced the rooting of cuttings with 1/2 or 3 leaves, whereas leafless cuttings failed to root regardless of treatment. Most of the 14C remained in the upper portion of the stem adjacent to the treated leaf; the mid-stem segment acquired about 40% of the activity. Little radioactivity reached the base of fresh cuttings, but upon rooting it accumulated 4 times the percentage of 14c found in comparable non-rooting bases. In all cuttings the incorporation of 14C into starch was much greater in the mid-stem than in the base. As much as 75% of the radioactivity in rooted bases was recovered in a residue remaining after ethanol soluble substances and starch were removed. The level of starch declined continually in the base but decreased in the mid-stem only at the end of the study. The concentration of sugars in both segments was relatively constant while that of sorbitol declined markedly and was hardly detectable in rooted bases. The largest loss of carbohydrates occurred in the bases treated with IBA. The similarity in levels and trends of carbohydrate utlization in the bases of cuttings with or without leaves indicated that in this cultivar the stimulatory effect of leaves on rooting is not associated with their being a source of carbohydrates.