Chilling Period Research Articles

Capacidade de germinação e quebra de dormência em sementes de cultivares de videira

Com a finalidade de gerar plântulas para o melhoramento genético, investigou-se a germinação de sementes de uva estudando-se a estratificação a frio, a aplicação de giberelina e a interação desses fatores. A conjugação de períodos de estratificação maiores que 13 dias com doses de giberelina (GA3) mostrou-se útil na quebra da dormência e na redução do seu tempo. A dose ideal de GA3 foi encontrada ao redor de 2.000 ppm e o menor período de estratificação, de cerca de 32 dias. Sementes de 61 progenitores potenciais foram germinadas em vasos com terra, mostrando-se a maior parte deles apta a ser usada em programas de melhoramento, com germinação superior a 45%, após os tratamentos indicados.

Protandry in the Green-Veined White Butterfly, Pieris napi L. (Lepidoptera; Pieridae)

1 Protandry, the earlier emergence of males relative to females, can be an optimal mating strategy in both sexes and should occur most strongly under male polygyny and female monogamy. Depending on life history and phenology, the importance of maintaining protandry may differ between the sexes and different generations. 2 To assess which sex accomplished protandry in the overwintering generation of the polyandrous butterfly Pieris napi L, we estimated for male and female pupae: (1) proportion that remained in diapause after 2-8 months at 40C; (2) postdiapause development time at 17, 20 and 230C after 4-8 months at 40C; and (3) daily weight loss (which is indicative of development rate). 3 Diapause was terminated after 4-6 months at 4 C and was broken somewhat earlier in male than in female pupae. Male postdiapause pupae developed on average 1 44 days faster than females and development time decreased with increasing chilling period in both sexes. Daily weight loss of postdiapause pupae started at a higher level and increased more rapidly in male than in female pupae. Hence, postdiapause development in P. napi exhibited phenotypic plasticity and protandry appeared to be maintained by both sexes. Key-words: Protandry, Pieris napi, postdiapause development

Diurnal Chilling Sensitivity and Desiccation in Seedlings of Tomato

Abstract Seedlings of six cultivars of tomato (Lycopersicon esculentum Mill.) showed differences in chilling sensitivity depending on the time during the diurnal light/dark cycle when they were placed at low temperature. In all cultivars, sensitivity was highest when the chilling exposure started at the end of a dark period, although the magnitude of the diurnal variation differed among the cultivars. When roots were removed prior to or just after chilling, injury also appeared earlier in seedlings whose chilling was started at the end of a dark period. Seedlings chilled starting at different times during the diurnal cycle had similar stomatal conductance values during chilling. It appears that diurnal changes in chilling sensitivity are not due to altered root function during or following chilling exposure, nor to variations in desiccation during the chilling period resulting from diurnal differences in stomatal conductance.

Amelioration of Chilling Injury in Rice Seedlings by Mefluidide1

Rice (Oryza sativa L.) seedlings at two to three leaf stage were used for testing mefluidide (/V‐[2,4‐dimethyl‐5‐[[(trifluoromethyl)‐ sulfonyl)amino]phenyl]acetamide) protection of chilled plants. After 8‐days exposure to 6°C, seedlings sprayed with 3, 5,10, and 15 mg mefluidide L−1 had 29,30,29, and 31% injury, respectively. Controls showed > 65% damage. During the 8‐day chilling period, consistent levels of about 30% electrolyte leakage were observed among the mefluidide‐treated plants, whereas controls showed an increase in leakage from 30 to 70%. It appears that mefluidide may alter plasma membrane properties and thus lead to increased tolerance to chilling stress. Significant protection was apparent 6 h after mefluidide treatment. Protection can last for at least 72 h after treatment. Chilled, mefluidide‐treated plants grew taller and flowered 5 to 10 days earlier than chilled controls. Although high concentrations of mefluidide can stunt plant growth, at concentrations of 5 to 10 mg L−1 rice plants did not exhibit any adverse growth and development characteristics. A 5 mg mefluidide L−1 application appeared to stimulate plant growth in a nonstressed environment.

EFFECTS OF BLAST-CHILLING CARCASSES OF DIFFERENT WEIGHT AND FATNESS ON THE APPEARANCE OF FRESH PORK

Pork carcasses (n = 773) were selected at random from the moving rail of a federally inspected abattoir approximately 35 min following slaughter. All carcasses were weighed and measured for fat thickness by a ruler on the mid-line of the carcass at the point of maximum fat depth over the loin. One side of each carcass was conventionally chilled for 24 h at 1 °C. The other side was blast-chilled at −25 °C in a blast-chilling tunnel for approximately 1 h followed by 23 h of cooling at 1 °C. Left and right sides were alternated for each chilling treatment. Following the chilling period pork sides were fabricated into the major primal cuts. Boneless pork loins and whole hams were subjectively assessed for muscle color (1 = very pale, 5 = very dark) and structure (1 = extremely soft and exudative, 5 = firm and dry) using established standards. Blast-chilled loins were significantly darker (P < 0.001) and had a firmer structure (P < 0.01) than conventionally chilled loins. Ham color was also darker (P < 0.001) for the blast-chill treatment but chilling treatment had a less clear effect (P = 0.07) on ham structure. Chilling treatment effects were similar (P > 0.22) on carcasses of different weight and depths of subcutaneous fat. It was concluded that blast-chilling carcasses resulted in fresh pork with a darker color and slightly firmer structure than carcasses chilled in a conventional manner. Key words: Carcass, pork, quality, blast-chilling, PSE, DFD

A time-interval activation of esterase A4 by cold: Relation to the termination of embryonic diapause in the silkworm Bombyx mori

The inactive esterase A4 (Ease A4) purified from the diapausing eggs of the silkworm, Bombyx mori, was chilled in vitro. The enzyme activity was very low during the early chilling period and it was suddenly elevated at a certain time of the chilling (2 weeks or less after chilling), depending upon when the chilling period began, and was followed by a rapid fall. The sudden elevation of the Ease A4 activity in vitro is equivalent to that observed in vivo and is coincident with the chilling period, the latter being indispensable for diapause termination. Data are also presented that suggest that the cold-induced activation of the Ease A4 may result from an autonomous structural change of the enzyme molecule which proceeds gradually in the cold.

The behaviour and coupling of the photoreceptor and hour-glass photoperiod timer at low temperature in the aphid Megoura viciae

In Megoura viciae photoperiodic time is measured during the scotophase by an hour-glass mechanism which is temperature compensated within the range 6–20°C. At lower temperatures the clock “loses time”, running at about half the normal rate at 0°C. The present experiments, based on the analysis of critical night lengths, showed that for short periods of scotophase chilling (4h or less) the same diminished rate is maintained irrespective of the position of the low temperature period within the scotophase. This occurs despite the known changes in spectral sensitivity of the photoreceptor. With longer periods of chilling (>6h) a normal critical response was not observed unless several hours of darkness intervened between the end of the chilling period and the temperature-modified critical night length. This is interpreted as a “recovery” process involving the photoreceptor but not the hour-glass. Additional data indicated that the sequence of changes in the photoreceptor, including the early resetting phase, is closely coupled to the progression of the timer even when photosensitivity is temporarily impaired by low temperature.

Diapause in Meloidogyne Naasi Eggs I. the Effect of Constant Temperature Incubation On Subsequent Hatch

Eggs of Meloidogyne naasi populations from Belgium, France, Germany, Wales, New Zealand and U.S.A. (California) were hatched at 20°C after incubation at constant temperatures (between 0° and 40°C) for periods up to 20 weeks. Pre-treatment hatch was low for all populations at all temperaturcs. The majority of eggs of all populations hatched at 20°C following (temperatures in the range of 0° to 15°C for a minimum time of 6 weeks) but the most favourable combination of temperature and time of incubation varied with population. Hatch at 20°C was also increased by incubation at warm temperatures (25° to 35°C) in all populations, but the effect was more variable and less marked than chilling temperatures. Embryonation was delayed or stopped at temperatures below 15°C and above 30°C but was resumed following transfer to 20°C. High mortality was recorded at temperatures above 30°C. Infectivity of artificially hatched juveniles was less than that of those which emerged following a chilling period.

The in vitro biosynthesis and secretion of glycerol by larval fat bodies of chilled Ostrinia nubilalis

Fat bodies from diapausing fifth-instar larvae of Ostrinia nubilalis were incubated in vitro at 5 or 23°C in Grace's medium and the glycerol contents of the organ and incubation medium determined. Fat bodies from diapausing larvae chilled 3 weeks at 5°C secreted glycerol into the medium at 5°C at a net rate of approx. 0.75 nmol/mg fat body dry wt/h for at least 96 h while the tissue levels remained essentially constant. Depending upon the experiment, from 6 to 15 times more glycerol was produced in 24 h at 5°C by these fat bodies than by those taken from diapausing unchilled larvae and incubated at either 5 or 23°C. A minimal chilling period of 10–12 days was recognized as necessary for chilled larval fat bodies to demonstrate rates of glycerol synthesis greater than those of unchilled larvae and the lag showed a temporal correlation with changes in haemolymph glycerol concentrations. These results suggest that this response to chilling by O. nubilalis is relatively slow. While incubation, at 23°C, of fat bodies from previously chilled larvae did not result in cessation of glycerol secretion, the rate of its appearance in the culture medium decreased during the 24-h incubation period. Although the ability of chilled fifth-instar larvae to accumulate glycerol is not dependent upon the diapause state results show that clearance of glycerol from the haemolymph by rewarmed O. nubilalis is related to diapause intensity.

Some aspects of induction and termination of diapause in a Greek strain of the miteTetranychus cinnabarinus (Boisduval) Boudreaux, 1956 (Acari: Tetranychidae)

A Greek strain of the miteTetranychus cinnabarinus, collected from ivy (Hedera spec.) in Thessaloniki (41 °N), exhibits a facultative, imaginal diapause. Diapause is induced by photoperiod and the photoperiodic response is of the long-day type. The critical daylength is 12.5 h at 19 °C. A period of chilling is not necessary for the termination of diapause under long-day conditions. Diapausing females are sensitive to photoperiod at least during the first 11/2 month of diapause.

THE DETERMINATION OF THE TENDERNESS ATTRIBUTE OF HOT BONING AND DELAY CHILLING OF MATURE COW CARCASSES

ABSTRACTRecent research has suggested the potential for upgrading some muscles from the mature cow carcass to be used as steak and roasts. With the application of modern processing techniques, beef from mature cow carcasses shows a potential to be utilized as salable retail roast and steak. The advantages of such processing techniques could minimize labor and energy usage. This study was undertaken to compare tenderness of mature cow steak and roast which were “hot” or “cold” boned. Six mature cow carcasses were utilized in this study. One side of each carcass was randomly assigned to be delay chilled at 16°C for 4 h before fabrication into muscle and muscle systems. The remaining side was assigned the conventional treatment with muscle excision after a 48 h chilling period at 1°C. Meat tenderness was objectively evaluated by the use of the Warner‐Bratzler Shear. Subjective evaluation of meat tenderness was by a trained taste panel. Muscles utilized in this investigation were the longissimus (LD), psoas major (PM), and quadriceps femoris (QF). Shear force values were generally small with less than .98 kg of shear force between treatments. Taste panelists were unable to distinguish between treatment, supporting the findings indicated by the mechanical measure.

Quantitative Measurements of Mefluidide Protection of Chilled Corn Plants

Abstract Leaves of mefluidide-treated corn (Zea mays L.) plants showed significant protection from chilling injury compared with untreated, chilled controls. On a per-plant basis, leaves sprayed with 5, 10, 15, or 20 ppm mefluidide had 6%, 14%, 9%, or 12% damage, respectively, of the total leaf area after a 6-day exposure to 4°C, whereas controls had more than 60% damage. Treated plants had more leaf area, were taller, had greater fresh and dry weights, and flowered 6 days earlier than controls. Plant growth was stunted with a 20-ppm spray, although plants were protected from chilling injury. During a 6-day chilling period, a consistent level of about 10% electrolyte leakage was observed among treated plants, whereas from control tissue, electrolyte leakage increased from 10% to 40%. These results suggest that mefluidide may modulate the permeability of the plasma membrane in the chilling environments. Chemical name used: N-[2,4-dimethyl-5-[(trifluoromethyl)sulfonyl]amino]phenyl]acetamide (mefluidide).

Time of flowering in spring: Its regulation in temperate zone woody plants

Certain cultivars ofMalus growing at Geneva, New York, USA, begin growth and bloom 2 –3 weeks later than commercial cultivars of apple. Our research suggests that these late bloomers bloom late because they have a very high chilling requirement for bud burst. The chilling requirement interacts with the heat requirement for bud burst in such a way as to result in delayed bud burst and bloom. Abscisic acid (ABA) decreases in the terminal buds of both early and late bloomers during the chilling period, but it decreases more rapidly in the early bloomers. It has not been determined if ABA plays a role in controlling bloom date.

Glycogen phosphorylase activity in flight muscles of Locusta migratoria at rest and during flight : Isolation of three forms of the muscle enzyme

In unflown locusts and in locusts flown for periods up to 30 sec about 70% of total flight muscle phosphorylase is in the active form. Longer periods of flight and chilling of unflown locusts both result in a partial inactivation of the enzyme. These results indicate that, if the muscle enzyme is predominantly in the inactive form in resting locusts its activation is a rapid process. Fractination of phosphorylase on DEAE-Sephacel produces three activity peaks ( I, II, III) which may be characterized by their AMP-dependency as phosphorylase b ( I) ab ( II) and a ( III). In chilled locusts total activity was accounted for by 33.8% phosphorylase b, 36.7% phosphorylase ab and 29.5% phosphorylase a; after 10 sec of flight by, respectively, 10.7, 15.2 and 74%. The three forms of the enzyme have been purified by affinity chromatography and were homogenous as judged by PAGE. Subunit molecular weight was estimated at 94,000 by SDS-PAGE. Gel filtration revealed a dimeric form of the enzyme with a mol. wt of 175,000.

Hot cutting of goat carcasses following early post-mortem high temperature ageing

Hot cutting of goat sides into bone-in joints, such as leg, shoulder and loin, 3 h after the sides were left hanging at an ambient temperature of 34°C with (treatment II) or without (treatment I) subsequent chilling prior to freezing did not adversely affect colour of meat, tenderness, cooking loss or water-holding capacity compared with normal chilling. The latter process (treatment III) significantly (P < 0·05) increased evaporative weight loss from the sides. Differences in colour, shear force, evaporative weight loss, cooking loss, drip loss from the leg joint and water-holding capacity between treatment I, where sides were hung at room temperature for 3h, and treatment II, where sides were given an additional chilling period of 21h after hanging, were not significant. These findings indicate that, in countries with ambient temperatures above 30°C, goat sides or carcasses can be cut hot after a 3h hanging period at ambient temperature and subsequently frozen without deterioration in the quality or processing properties of the meat.

Effect of hibernation length on termination of diapause in European Tettigoniidae (Insecta: Orthoptera).

The effect of the length of cold treatment on development time of embryos of eight Central European tettigoniid species was investigated in laboratory experiments, using chilling periods of 3, 4, 5, 6, 9, and 12 months. Two different types of response were observed: (1) The hatching date was not influenced by hibernation length (Conocephalus) or only after the 3-month cold treatment (Phaneroptera, Platycleis), or (2) The time required for post-diapause development was significantly reduced by each 1-month increase in the length of cold treatment up to 6 months (Meconema, Metrioptera, Tettigonia).Thus, the correct timing of hatching is achieved by one of two different strategies. In lat-hatching species, the influence of hibernation length is small. Premature appearance is prevented by a high thermal threshold. In early-hatching species, the embryos are obviously able to measure the length of the chilling period. Thus, they gradually change their physiological state so that the potential speed of postdiapause development increases as the 'winter' is prolonged. This strategy can be understood as an adaptation to the necessity of hatching at low or moderate temperatures. Field experiments with two Tettigonia species confirm the laboratory data.

Egg Temperature and Embryo Metabolism in Some High-Latitude Procellariiform Birds

The embryos of Procellariiformes develop slowly, reportedly, at least in part, as a result of low incubation temperatures, and some species such as Wilson's and Leach's storm petrels experience long periods of chilling. Incubation temperatures of eggs of Leach's storm petrel (on Kent Island, New Brunswick), Wilson's storm petrel, and the southern giant fulmar (Palmer Station, Antarctica) averaged 35.9, 35.7, and 35.5 C, respectively. These are well within the range of temperatures for other species of birds and indicate that the prolonged incubation periods of petrels are not attributable to low incubation temperatures. We measured the depressing effect of cooling (Q10) on rate of heartbeat of small embryos and rate of oxygen consumption of larger embryos. Values of Q10 increased at lower temperatures but in most cases did not differ from, or in some cases even exceeded, the values for embryos of species that lack cooling tolerance. Large embryos of the giant fulmar, which has slow embryonic development but continuous incubation, did not survive prolonged chilling, indicating that not all slowly developing embryos tolerate protracted cooling, at least in their late stages of development. Rates of oxygen consumption by storm petrel embryos were about two-thirds the level of the similarsized but rapidly growing Japanese quail embryo. Giant fulmar embryos exhibited low rates of oxygen consumption, as do other Procellariiformes, but, surprisingly, so did the rapidly growing skua embryos.

Quantitation of Chill-Induced Release of a Tubulin-Like Factor and Its Prevention by Abscisic Acid in Gossypium hirsutum L.

The degree of tubulin polymerization in cotton (Gossypium hirsutum L. cv Acala) cotyledonary tissue was estimated by radioimmunoassay which measured the amount of a tubulin-like factor. It was assumed that the release of this tubulin-like factor indicated depolymerization of microtubules. Exposure to chilling resulted in complete release of the tubulin-like factor. Pretreatment with abscisic acid in the light almost completely prevented the chill-induced release of the tubulin-like factor. Addition of colchicine during the chilling period accelerated the release of the tubulin-like factor. Pretreatment with abscisic acid greatly reduced this effect of colchicine. It is concluded that the destruction of the microtubular network is involved in the development of chilling injury in cotton. Abscisic acid apparently decreased chilling injury by stabilization of the microtubular network.

Changes in the Levels of Endogenous Cytokinin-like Substances During Cold-induced Germination of Acer platanoides L. Seeds

Summary Embryo-dormant seeds of Acer platanoides show a clearly defined but transient peak of endogenous cytokinin-like substances during the early stages of germination following an inductive chilling period. Maintenance of the fruits at chilling temperatures until germination was visible probably extended the period over which these changes in cytokinin levels occurred, making their observation easier. It seems likely that this transient peak of cytokinin activity in germinating Acer platanoides seeds is analogous to the ephemeral peaks in cytokinin activity observed in the germination of non-dormant species. The possibility that there are two transient peaks of cytokinin-like activity in embryo dormant seeds, one that is related to the breaking of dormancy and a second that is related to the germination, is discussed.

Stomatal Behaviour and Water Relations of ChilledPhaseolus vulgarisL. andPisum sativumL.

Leaf diffusion resistance interpreted as stomatal resistance, leaf water potential ((//w), solute potential (y/s) and leaf turgor potential (^p) of the chilling sensitive species Phaseolus vulgaris were determined during chilling at 4 °C in the light. Both chill-hardened and non-hardened plants were used. For comparison, the chilling resistant species Pisum sativum was also used. The results for chilled P. sativum were similar to those obtained for chill-hardened P. vulgaris plants receiving a chilling treatment. In both cases a reduction in stomatal aperture and the maintenance of a positive leaf turgor were the responses to chilling. Leaves of chilled but non-hardened P. vulgaris plants were found to maintain open stomata throughout the chilling treatment despite a severe wilt developing after 7 h at 4 °C. This was in contrast to the chill-resistant P. sativum, which showed a rapid closing and subsequent re-opening of the stomata to a new reduced aperture. During the first 12 h of chilling i//w of P. vulgaris leaves changed from —0-47 MPa to - 1 -24 MPa. On more prolonged chilling y/w tended to return to pre-chilling values. In addition, i//p decreased from 0-42 MPa to zero after only 9 h of chilling, and remained at this value for the remainder of the chilling period. y/s changed rapidly from -0-89 MPa to -1-35 MPa in the first 7-5 h, and after 9 h. (//w and t//s were equal, i.e. zero i//p. In contrast, the chilling resistant plant P. sativum maintained a positive i//v throughout the chilling period, and there was little difference between values of i//w and i//s in control and chilled leaves.