Benefits of ethylene removal during apple storage

The potential use of an ethylene absorbent in controlled atmosphere storage of two varieties of apple has been investigated. With Golden Delicious, the rise in ethylene concentration during controlled atmosphere storage can be delayed for about 40 days but not prevented by inclusion of potassium permanganate in the storage container. But with Bramley's Seedling, potassium permanganate can delay ethylene accumulation for over 200 days. Ethylene treatment of Bramley's Seedling in a flowing stream of 5% CO₂:3% O₂:92% N₂ caused accelerated softening, accumulation of α-farnesene and earlier onset of superficial scald. Use of potassium permanganate to remove ethylene during storage in static controlled atmosphere conditions retarded all three processes in Bramley's Seedling kept in 5% CO₂:3% O₂ and in 9% CO₂:12% O₂. However, in one experiment, ethylene removal in 5% CO₂:3% O₂, led to external and internal symptoms of CO₂ damage. A subsequent investigation of the combined effects of harvest date, store temperature and ethylene removal in 5% CO₂:3% O₂ did not show any damage or accumulation of succinic acid which is known to be involved in CO₂ injury. This experiment revealed that ethylene removal could be successfully accomplished on Bramley fruit harvested up to a month after the usual date and little α-farnesene accumulated in this fruit. Nevertheless scald did develop on late picked fruit and this raises doubts about the causal role of farnesene in scald.     

The ultrastructure of apple cells during storage

A study was made of ultrastructural features of epidermal and hypodermal cells of freshly collected apples of early- and late-ripe cultivars, and of those storage at low temperature. In late-cultivars, the ultrastructure of most cells remained unchanged within 8 months (except increased vacuolation). In early-ripe cultivars, signs of senile destruction were evident in many hypodermal cells as early as within 2 months of storage. Apple cells of all cultivars contained a fairly developed smooth endoplasmic reticulum (SER). A suggestion is made that SER may be involved in the synthesis of abscisic acid essential for the fruit dormancy maintenance.     

Heat-induced changes in respiratory pathways and mitochondrial structure during microcycle conidiation of Neurospora crassa

Changes in both respiratory pathways and mitochondrial structure of Neurospora crassa occurred under conditions of microcycle conidiation. Upon heat-treatment at 46°C, conidia developed a highly cyanide-insensitive, hydroxamate-sensitive respiration associated with morphological alterations in mitochondrial membranes; such changes were time-dependent. When heat-treated conidia were shifted down to 25°C, the alternate, hydroxamate-sensitive respiration decreased significantly, paralleling the recovery of well-cristated mitochondria with an electron-dense matrix in the germ tubes. The decrease in hydroxamate-sensitivity was associated with two periods of increase in cyanide sensitivity corresponding to the events of germination and precocious proconidial budding.     

Changes in the structure of apple pectic substances during ripening and storage

During ripening, the degree of polymerization, the degree of esterification, the neutral sugar content and the neutral sugar composition of extractable apple pectic substances did not change. Some xylose and glucose containing polysaccharides can be extracted from the ripe cell walls suggesting that changes in the hemicelluloses take place. In senescent apples, significant changes in the structure of apple pectic substances could be observed. The degree of polymerization of both the galacturonan chains and the arabinogalactan side chains decreased. The amount of water-extractable pectin molecules carrying 1,3/1,6-linked galactans increased. The degree of esterification and the distribution of the methoxyl groups in the apple pectic substances did not change very much.     

Metabolic changes in rat skin during preservation and storage in glycerol buffer at -196 degrees C.

The penetrating cryoprotective glycerol dissolved in different concentrations in buffer medium effectively protects skin tissue against freeze-thaw injury when progressively cooled to ?196 °C followed by a fast warming-up rate. Upon incubation of the tissue after storage, the incorporation of [2-¹⁴C]glycine into the proteins, of [6-³H]thymidine into DNA, and α-[1-¹⁴C]aminoisobutyric acid transport through the cell membrane are reduced compared to freshly incubated skin. An essential loss in metabolic activity occurs during exposure of the skin to the preserving buffer. Although the length of storage does not seem to affect the final viability, the actual freezing and thawing procedures are particularly damaging to tissue already injured by previous exposure to buffer containing cryoprotective agents.     

Ontogenetic changes in pacemaker activity in chick heart

Pacemaker activity of the isolated chick heart changed considerably during development. The spontaneous impulse frequency increased up to the 11th–15th incubation day. This period of acceleration was followed by a marked deceleration around the time of hatching. Both acceleration and deceleration appeared to be caused by changes intrinsic to the pacemaker. Deceleration was related to a decrease in rate of slow diastolic depolarization. The results were compared with well-known ontogenetic changes in heart rate $\text{in vivo}$. This comparison indicates that the deceleration of pacemaker firing around hatching is counteracted by the development of sympathetic cardiac reflexes $\text{in vivo}$.     

Ontogenetic variation in chemical and physical characteristics of adaxial apple leaf surfaces

The reaction of plants to environmental factors often varies with developmental stage. It was hypothesized, that also the cuticle, the outer surface layer of plants is modified during ontogenesis. Apple plantlets, cv. Golden Delicious, were grown under controlled conditions avoiding biotic and abiotic stress factors. The cuticular wax surface of adaxial apple leaves was analyzed for its chemical composition as well as for its micromorphology and hydrophobicity just after unfolding of leaves ending in the seventh leaf insertion. The outer surface of apple leaves was formed by a thin amorphous layer of epicuticular waxes. Epidermal cells of young leaves exhibited a distinctive curvature of the periclinal cell walls resulting in an undulated surface of the cuticle including pronounced lamellae, with the highest density at the centre of cells. As epidermal cells expanded during ontogenesis, the upper surface showed only minor surface sculpturing and a decrease in lamellae. With increasing leaf age the hydrophobicity of adaxial leaf side decreased significantly indicated by a decrease in contact angle. Extracted from plants, the amount of apolar cuticular wax per area unit ranged from only 0.9 microgcm(-2) for the oldest studied leaf to 1.5 microgcm(-2) for the youngest studied leaf. Differences in the total amount of cuticular waxes per leaf were not significant for older leaves. For young leaves, triterpenes (ursolic acid and oleanolic acid), esters and alcohols were the main wax components. During ontogenesis, the proportion of triterpenes in total mass of apolar waxes decreased from 32% (leaf 1) to 13% (leaf 7); absolute amounts decreased by more than 50%. The proportion of wax alcohols and esters, and alkanes to a lesser degree, increased with leaf age, whereas the proportion of acids decreased. The epicuticular wax layer also contained alpha-tocopherol described for the first time to be present also in the epicuticular wax. The modifications in the chemical composition of cuticular waxes are discussed in relation to the varying physical characteristics of the cuticle during ontogenesis of apple leaves.     

Ontogenetic changes in tolerance to herbivory in Arabidopsis

Tolerance to herbivory—the ability of plants to maintain fitness despite herbivore damage—is expected to change during the life cycle of plants because the physiological mechanisms underlying tolerance to herbivory are linked to growth, and resource allocation to growth changes throughout ontogeny. We used the model plant Arabidopsis thaliana to test two hypotheses: that tolerance increases as plants grow, and that tolerance decreases at the onset of reproduction. We chose three accessions previously reported to vary for resistance to herbivory in order to explore whether tolerance and resistance are inversely related. Cabbage looper (Trichoplusia ni) larvae were allowed to feed on plants at either the four-leaf, six-leaf, or 1st-flower developmental stage until 50% of the leaf area was removed. Overall, we found a trend for increased tolerance with ontogenetic stage, but there were important differences among accessions in their response to herbivory at different stages. Tolerance did not decrease with the onset of flowering, nor did we find any correlation between resistance and tolerance levels. Three main plant traits correlated strongly with tolerance: stem mass, an earlier onset of reproduction and a longer fruiting period. This study suggests there may be considerable variation in ontogenetic patterns of tolerance in natural populations of A. thaliana, and warrants further investigations with more accessions or natural populations, and detailed measurements of traits purported to contribute to tolerance in our quest to understand the mechanisms of tolerance to herbivory.     

Fine-tuning of the flavonoid and monolignol pathways during apple early fruit development

Planta - A coordinated regulation of different branches of the flavonoid pathway was highlighted that may contribute to elucidate the role of this important class of compounds during the early...     

Ontogenetic changes in temperature preference of Atlantic cod

Final thermal preferendum ( T ) experiments were conducted in a horizontal thermal gradient tank from the beginning of August 2001 to mid‐November 2001 using Atlantic cod Gadus morhua from 6·5 to 79·0 cm fork length ( L _F). The value of T varied significantly ( P  < 0·005) with L _F( T  = 7·23–0·054 L _F), with smaller (younger) fish choosing higher temperatures than larger (older) fish. The preferendum varied from 6·9° C for fish of 6·5 cm to 3·0° C for those of 79·0 cm. Experiments comparing fish positions in the gradient tank between thermal gradients of 0·5–11·0 and 4·5–14·5° C demonstrated that fish positions were determined by temperature selection instead of undesirable tank effects. This study is the first to demonstrate the effect of ontogeny on temperature preferences of a marine fish species.     

Morphological changes of mouse spermatozoa during in vitro storage

In addition to normal spermatozoa, spermatozoa with bent and coiled tails, as well fragments of spermatozoa, such as single heads and tails and complexes of heads and tails, were found in a suspension of epididymal spermatozoa obtained from mice kept in the state of sexual deprivation for a long time. The dynamics of these elements was traced in the suspensions maintained at 10 and 35°C. At 37°C, the numbers of normal spermatozoa and spermatozoa with bent tails significantly decreased, while that of spermatozoa with coiled tails remained unchanged. At 10°C, the number of only spermatozoa with bent tails decreased. Based on the published data and our results, we propose that spermatozoa unclaimed for fertilization not only disintegrate into characteristic fragments, but also undergo a sequence of forms characteristic for the haploid phase of multicellular organism life cycle.     

Phytohormone changes during storage root growth in Beta species

The physiological and morphological factors necessary for efficient accumulation of sucrose in sugar beet (Beta vulgaris L.) are considered in relation to potential uses of plant growth regulators to modify the anatomy of storage roots so as to increase sucrose content and yield. The percentage of sucrose in root fresh and dry matter is closely related to root structure. Sugar beet, mangold and chard are three sub-species of Beta vulgaris that differ considerably in their anatomy, assimilate partitioning, sucrose concentration and root dry matter yield. The concentrations of indole-3-acetic acid (IAA), abscisic acid (ABA) and cytokinins were measured during the growth of the storage root in each of these cultivars. Correlations were found between the phytohormone levels and the formation of secondary cambia and their subsequent cell division and expansion activity.     

Ethylene binding changes in apple and morning glory during ripening and senescence

Ethylene binding sites were measured during fruit ripening and morning glory flower senescence. Little change in ethylene binding was noted during these developmental stages, except a slight decline during the later stages of fruit ripening or flower senescence. The concentration of ethylene required to achieve 50% saturation of the binding sites was 0.14 l/liter for both apple pulp and morning glory flowers. Ethylene binding sites were calculated to be 3.2×10^–11 moles/kg and 3.8×10^–9 moles/kg in apple and morning glory, respectively. It does not appear that changes seen in ethylene sensitivity during fruit ripening can be readily ascribed to changes in the number of ethylene binding sites in the tissue.Paper No. 11398 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC 27695-7601, USA.     

Alternation of respiratory pathways during the development of wheat leaf

P?i vývoji listu p?enice se zmen?uje stupeň inhibice dýchání fluoridem, monojodacetátem a malonátem a poměr mezi radioaktivitami¹⁴CO₂ uvolněného z glukosy-6-¹⁴C a glukosy-l-¹⁴C (C₆/C₁), co? svěd?í o zvět?ování podílu pentosovího cyklu v celkové respiraci. Tato změna v?ak neni zp?sobena absolutním zvět?ením aktivity pentosového eyklu u star?ích list?, nýbr? p?edev?ím poklesem aktivity glykolytického systému. Naproti tomu u list? oddělených od obilky se pri sní?ení vlhkosti atmosféry méní poměr mezi dýchacími cestami v d?sledku aktivace pentosového cyklu. Na základě disproporce mezi procentem glykolytického podílu respirace vypo?tenym ze sní?ení poměru C₆/C₁ p?i inhibici dýchání fluoridem a procentem inhibice dý chání fluoridem bylo diskutováno o mo?ných p?íoinách vysokých poměr? C₆/C₁ u mladých list?, u nich? byly v některých p?ípadech zji?těny hodnoty těchto poměr? dokonce vy??í ne? jedna.     

Ontogenetic changes in potassium transport in xylem of tomato

The influence of plant ontogeny on xylem exudate K⁺ concentrations and K⁺ transport to the shoot was studied in both nutrient-solution and field-grown tomato plants ( Lycopersicon esculentum ).
K⁺ concentrations in xylem exudate from decapitated plants decreased during tomato plant development from a high of 12 m M to a low of 5 m M . In the nutrient-solution plants, the most rapid decline occurred during the vegetative growth phase, while in field-grown plants, the xylem K⁺ concentrations remained high during an-thesis and then subsequently declined. The rapid decline in nutrient-solution plants might be related to a decrease in the absorptive efficiency of the root system. In field-grown plants, a reduction in the availability of assimilates to the root might account in part for the decrease in xylem exudate K⁺ concentrations. The volume (ml h⁻¹ plant⁻¹) and the net rates of K⁺ exudation (mmol h⁻¹ plant⁻¹) decreased dramatically as the fruits approached maturity. Since only a small reduction in xylem exudate K⁺ concentrations occurred during fruiting, the hydraulic conductivity of the root system decreased as the tomato plants aged. It is proposed that the ontogenetic changes in xylem transport of K⁺ contribute to a reduction in leaf free space K⁺ concentration which would explain the decline in tomato leaf K⁺ concentrations.