Parenchyma cell growth in potato tubers I. Different tuber regions

Enlargement rates of starch-storage parenchyma cells during growth of Kennebec and Russet Burbank potato cultivars were determined for cortical, perimedullary, and pith tissuues of bud ends, midsections, and stem ends of tubers. Average volumetric size of parenchyma cells increased 7 to 18x during growth of Russet Burbank tubers, with the greatest increases occurring in cortical and perimedullary cells of bud ends and midsections, and the least in stem ends and pith tissues. In Kennebec tubers parenchyma cells in both stem end and midsection increased only 5 to 8 x, whereas increases in bud ends ranged from 8 to 20 times. Cell enlargement to tuber enlargement ratios appproached unity early in growth of Russet Burbank tubers. As tubers increased beyond the 45 g size, cell enlargement and tuber enlargement rates were essentially equal. Calculations of cells per unit tissue volume agreed with ratio determinations. The timing of such unity appeared to be delayed in Kennebec tubers, and was not quite as pronounced as in Russet Burbank tubers. This may have been due to differences in growth rates of individual tubers in response to cultural conditions. In general, cells of harvestmature Kennebec tubers were about 60% as large as similar cells of Russet Burbank tubers.     

Studies on phenolase and internal discoloration (blackspot) in Russet Burbank potatoes

In an investigation of phenolase-blackspot relationships, experiments were conducted to study sources of variability in phenolase determinations that could account for the inability to get consistent and reproducible data between trials. There was no reproducibility between trials in the pattern of apparent relationships between phenolase and blackspot when phenolase in bruised and unbruised tissue from blackspot-susceptible and-resistant tubers was calculated on a fresh-weight basis. Also, apparent blackspot-phenolase relationships differed with the type of substrate used. However, when phenolase activity was determined from freeze-dried tissue taken from some of the same tubers, the pattern of an apparent relationship between phenolase and blackspot became more clearly defined and was quite consistent when activity was calculated on either a dry-weight or protein basis, regardless of the substrate used. Reference to a company or product name does not imply approval or recommendation of the product by the U.S. Department of Agriculture to the exclusion of others that may be suitable.     

Anatomy and compositional variation within potatoes II. Phenolics,enzymes and other minor components

Minor components, including principal phenolics and certain enzymes, are distributed within the potato tuber according to patterns that are significant to many practical problems in the growing, handling, and utilization of potatoes. Chlorogenic acid is much more concentrated in outer than in inner tissue zones; is also highly concentrated in the phloem and phloem parenchyma tissues of both cortex and perimedullary zone. Tyrosine is generally distributed but is more concentrated in the stem end than in the bud end of the tuber and probably is also more concentrated in central than in outer tissues. Results of histochemical tests on distribution of these phenolics agree in general with quantitative analytical results. Phenolases and peroxidase also show characteristic patterns of distribution. Peroxidase affects tissue differentiation and specialization and shows strong histochemical relationship with cell-wall specializations. Phenolases show association with distributions of phenolic substrates and usually are associated with cell contents. Distribution patterns are reviewed for other minor constituents, such as, iron, copper, ascorbic acid, thiamine and solanin.     

Variables affecting sugar removal in freeze-leached potato strips

Strips cut from cold storage (5 C), potatoes were immersed in difluorodichloromethane (R-12) from 5 to 13 sec. This rapid freezing was found to selectively damage only the frozen cells and to increase their permeability with respect to intracellular soluble materials. Subsequent immersion in water (17 to 52 C) leached the soluble materials from the frozen cells. This method of leaching in 20 min removed less than 15% of the starch released by potato strips leached at 65 C for 15 min (simulated commercial conditions). The depth of freeze determined by physical methods and by analysis of the leached surface layers showed reducing sugar removal 0.1 to 0.2 mm below the calculated average depth of freeze. In experimental lots the weight of leached materials increased with increased freezing time. Manipulating freezing depth and leaching time made it possible to achieve the required sugar removal from different lots of tubers.     

Influence of ethylene on black spot of potato tubers

Sound, hand harvested, whole potatoes were exposed to continuous flowing atmosphere containing air, air with 3 or 5% CO₂, and air with concentrations of 0.5, 1.0, and 10ppm C₂H₄ for periods of 1 to 11 days at 20°C. At 1-day intervals, potatoes were bruised and black spot development assessed. Development of black spot in potatoes exposed to C₂H₄ was equal to or less than in potatoes at harvest. The severity remained low during 3-day exposure to 1 ppm C₂H₄ and after transfer to 4 days in air, then increased. Severity of black spot increased in potatoes exposed to air, with intermediate response from exposure to air with CO₂. With an increase in sprouting, differences in black spot among treatments diminished. Less black spot developed in immature than in mature potatoes.     

Catch rate and at‐vessel mortality of circle hooks versus J‐hooks in pelagic longline fisheries: A global meta‐analysis

We conducted a meta‐analysis of literature reporting on the use of circle hooks and J‐hooks in pelagic longline fisheries. Our study included more data than previous meta‐analyses of the effects of hook type, due to both a larger number of relevant studies available in recent years and a more general modelling approach. Data from 42 empirical studies were analysed using a random effects model to compare the effects of circle hooks and J‐hooks on catch rate (43 species) and at‐vessel mortality (31 species) of target and bycatch species. Catch rates with circle hooks were greater for 11 species, including four tuna species, six shark species and one Istiophorid billfish. Catch rates on circle hooks were lower for seven species, including two Istiophorid billfishes and two species of sea turtle. At‐vessel mortality was significantly lower with circle hooks in 12 species, including three tuna species, three Istiophorid billfishes, swordfish (Xiphias gladius) and three shark species. No species had significantly greater at‐vessel mortality when captured with a circle hook rather than a J‐hook. While our general approach increased model variability compared to more detailed studies, results were consistent with trends identified in previous studies that compared the catch rates and at‐vessel mortality (between hook types) for a number of species. Our results suggest that circle hooks can be a promising tool to reduce mortality of some bycatch species in pelagic longline fisheries, although the effects depend on the species and the metric (catch rate or at‐vessel mortality), emphasizing the need for fishery‐specific data in conservation and management decisions.     

Reproductive performance of postpartum ewes treated with insulin or progesterone hormones in association with ram effect

The reproductive performance of postpartum Santa Inês (SI) and Morada Nova (MN) ewes treated with insulin or progesterone hormones in association with ram effect was evaluated. Ewes from SI (n = 69) and MN (n = 69) breeds were randomly allocated to three groups of each breed (T1—ram effect only; T2—ram effect + insulin; T3—ram effect + progesterone). Progesterone concentrations (ηg/ml; mean ± SD) before and after introduction of rams (n = 6) were 0.51 ± 0.22 and 3.78 ± 0.68 (T1), 0.65 ± 0.21 and 3.77 ± 0.78 (T2) and 0.52 ± 0.21 and 3.84 ± 0.84 (T3) in SI ewes and 0.74 ± 0.19 and 3.71 ± 0.56 (T1), 0.70 ± 0.21 and 3.79 ± 0.75 (T2) and 0.81 ± 0.14 and 3.87 ± 0.80 (T3) in MN ewes, respectively. Thus, lower progesterone concentrations were found before the introduction of rams (p < .05). After the introduction of rams, preovulatory peaks of LH (ηg/ml) occurred at 28 (T1), 44 (T2) and 48 (T3) hr in SI ewes and at 64 (T1), 40 (T2) and 44 (T3) hr in MN ewes. The mean number of ovulations was similar between groups (p > .05), was 1.3 ± 0.51 (T1), 1.5 ± 0.54 (T2) and 1.6 ± 0.51 (T3) in SI ewes and 1.3 ± 0.51 (T1), 1.6 ± 0.51 (T2) and 1.6 ± 0.51 (T3) in MN ewes. In conclusion, the ram effect alone is effective at inducing and synchronizing oestrus in sheep under postpartum anoestrus, irrespective of hormone treatments.