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- Author or Editor: Patrick J. Breen x
Spring-budded trees of peach/plum (Prunus persica Batsch. cv. Fay Elberta on the plum P. cerasifera Ehrh. × P. munsoniana Wight & Hedr. cv. Marianna 2624) showed foliar symptoms of incompatibility in early August, whereas a reciprocal combination, plum/peach, remained healthy. Within 2 weeks leaves and scion bark of the incompatible combination contained several times the concentration of starch found in comparable tissues of peach/peach trees. The level of polyols were similar in the peach scions of both combinations until end of summer. In the plum rootstock starch in the bark of the incompatible trees reached a maximum concentration at the beginning of August but was essentially depleted within the next 3 weeks, while the level of sorbitol decreased by half. In relation to compatible combinations, free sugars increased in the bark above the incompatible union and declined below. Presumably, failure of the phloem to function across the peach/plum union in mid-summer resulted in the markedly dissimilar carbohydrate levels in the graft components.
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.
Sucrose was not detected in developing fruit of ‘Brighton’ strawberry (Fragaria × ananassa Duch.) until 10 days after anthesis. Thereafter, its concentration increased rapidly but then declined as fruit became red ripe. The concentration of glucose and fructose were similar and higher than that of sucrose during early fruit growth and in ripe fruit. Uptake of 14C-sugars was followed in excised disks of cortical tissue from fruit 15–17 days old. The addition of CaCl2 was necessary to maintain tissue respiration. Sucrose uptake into tissue disks was nearly constant over 4 hr and had a pH optimum of 5.0. Kinetic analysis of sucrose uptake revealed both linear and saturable components. The kinetic characteristics of fructose uptake was similar to those for sucrose. Glucose, however, was taken up much more rapidly than either sucrose or fructose and only demonstrated saturation kinetics. The metabolic inhibitors NaCN (5 mM), dinitrophenol (DNP, 3 Mm) and carbonyl cyanide m-chlorophenyl hydrazone (CCCP, 100 μM) stimulated sucrose uptake 34%, 94%, and 54%, respectively. DNP eliminated the saturable component. Uptake of sucrose was inhibited by 36% with 10 μm DNP, 16% with 5 mM glucose, and 16% in a 100% N2 atmosphere. After incubation in 14C-sugars for 2 hr, about 90% of the label recovered from disks was in a neutral fraction. Half or more of this was in either glucose or fructose, depending upon the sugar fed. The distribution of 14C between glucose and fructose moieties of sucrose isolated from tissue fed (14C-fructosyl) sucrose indicated that a portion of the sucrose recovered underwent hydrolysis and randomization. Similar results were found with sucrose isolated from attached, whole fruit 8 hr after abraded leaves were fed labeled sugars. Results suggest that sucrose may be hydrolized prior to uptake into fruit tissue.
In the article “Respiration and Weight Changes of Easter Lily Flowers during Development” by Yin-Tung Wang and Patrick J. Breen [HortScience 19(5):702-703] the captions for the 2 graphs were reversed
To simulate the developmental sequence of the Easter lily flower (Lilium longiflorum Thunb. ‘Nellie White’), flower buds from 4.5 cm to 16 cm (anthesis) were cut from field-grown plants on a single date. Fresh weight increased with bud length and was highest at anthesis, whereas dry matter reached a maximum of 1.6 g when buds were 14 cm long. The percentage of dry matter declined from 16% in the smallest bud to only 9% at anthesis. Respiration rates, both per bud and per unit dry weight, increased with bud size, reaching peak values of 3.0 mg CO2 · bud-1 · hr-1 and 1.8 mg CO2 · g-1 dry wt · hr -1 at anthesis before declining to a markedly lower rate. From these data, the total dry matter needs of flowers on field-grown plants were estimated.
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.
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.
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.
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.
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.