Chilling Pretreatment Research Articles

RESPONSE OF WHEAT PLANTS TO THE COMBINED IMPACT OF LOW TEMPERATURE AND CADMIUM

The response of wheat plants ( Triticum aestivum L.) to a combined (consecutive) impact of low temperature (4 ° С) and cadmium sulphate (100 µM) was investigated. Pretreatment of the seedlings with cadmium for 1 day caused an increase in cold tolerance, which continued during the following exposure to the 4 ° С temperature, reaching a maximum after 1–2 days, but decreasing somewhat in the end of the experiment (7 d). At the same time cadmium did not prevent the accumulation of fresh and dry biomass of the shoots at subsequent exposure of the seedlings to 4 ° С temperature, although it negatively affected the total chlorophyll content in the leaves. Pretreatment of the seedlings by chilling during 1 day also caused an increase in their cold tolerance, which persisted for a few days at subsequent exposure to cadmium, but decreased significantly in 6–7 days. Moreover, the chilling pretreatment decreased the accumulation of fresh and dry biomass of wheat shoots as well as the total chlorophyll content in the leaves at the subsequent prolonged cadmium impact. It was concluded that the response of wheat plants to a prolonged impact (7 d) of a low non-freezing temperature or cadmium changed significantly if preceded even by a short-term (1 d) treatment with the other stress factor. In particular, exposure to cadmium before chilling partially ‘disrupted’ the programme of cold adaptation, wherefore the plants’ resistance did not reach the level typical for cold hardening at a temperature of 4 ° С, and cold pretreatment of the plants, in turn, aggravated the negative effects of cadmium on cold tolerance, biomass accumulation and the content of photosynthetic pigments in wheat leaves.

Interannual variability of germination and cone/seed morphometric characteristics in the endemic Grecian fir (Abies cephalonica) over an 8-year-long study

AbstractAbies cephalonicacone and seed morphometric characteristics as well as seed germination behaviour were investigated during an 8-year-long diachronic study (2007–2015). The research was carried out in Parnitha National Park, in the part of this Greek endemic, silver fir population that was spared from an unprecedented wildfire (2007). A statistically significant interannual and among-tree variation of cone traits has been identified, except for cone diameter. Cone length is correlated to the number of seeds per cone, while the percentage of empty seeds has been consistently high, with extreme values of 29.3 and 81.8% in a masting (2015) and lean crop (2009) year, respectively. There is also a considerable proportion of dead (including infected) and non-germinated seeds, and the eventual germinable fraction is well below 25% with spikes in masting years (39.4 and 60.9% in 2010 and 2015, respectively). Untreated seeds have been tested at a wide range of constant and alternating temperatures and germination is completed within 4–5 weeks atT≥ 15°C andca15 weeks at 5–10°C. A chilling pretreatment of 4–8 weeks (at 2–4°C) concludes germination at 15–20°C within 2 weeks. A significant white light requirement has been observed for untreated seeds at 15–20°C, while germination was light indifferent at lower or higher temperatures. Data obtained in this study confirm the present, field seed germination during springtime; we may also predict an earlier germination (late autumn to mid-winter) in forest gaps, under the predicted, warmer conditions in the future.

CALLUS INİTİATİON FOR INDİRECT POLLEN EMBRYOGENESİS İN ANEMONE CORONARİA

In the present study, anther culture method was used in Anemone coronaria, known as Manisa Tulip in Turkiye, in order to obtain haploid plants. The anthers with uninucleate microspores of the flower buds, collected from an A. coronaria var. coccinea population, were used as explant. In the treatments, two basic tissue culture media (NN and B5) were tested with 4 different auxin concentrations and also 4 different auxin:cytokinin ratios. Anthers were subjected to a chilling pre-treatment for 7 days at +7°C in the dark and then incubated under continuous dark conditions at 25 +1°C. The use of cytokinin together with auxin increased callus induction frequency. It was also found that the treatments with the combinations consisting of both kind of growth regulators in B5 medium showed more successful performance.

Effects of Salinity and Temperature on Seed Germination in a Japanese Endangered Halophyte Triglochin maritimum (Juncaginaceae)

(Juncaginaceae). Germination tests were carried out at three salinity levels (0,200,400 mM NaCl in which seeds were exposed to increasing- or decreasing temperatures. Effects of moist-chilling pretreatment (stratification) in 0,200 and 400 mM NaCl on seed germination at 0,200 and 400 mM NaCl, respectively, were also examined. Under the highest salinity condition (400 mM NaCl), no germination was observed. The seeds germinated very well (88%) in fresh-water after 5-month moist-chilling pretreatment. Longer moist-chilling pretreatment resulted in higher germination percentages. Moist chilling pretreatment in 0,200 and 400 mM NaCl for 5 month enhanced germination percentages to 10% (in 400 mM NaCl) –88% (in 0 mM NaCl).

Development of a technique for in vitro unpollinated ovary culture in rice, Oryza sativa L.

A simple and efficient technique for in vitro unpollinated ovary culture in rice which is also applicable for indica genotypes was developed for breeding and genetic studies. Sampling explants at the auricle distance of 7–12 cm between the two uppermost leaves of a tiller, providing a chilling pretreatment and ovaries with 1/3 of the hulls intact gave optimum response to culture. For callus induction with the spontaneous breaking of ovaries, N6 media supplemented with NAA (2 mg/l) and DMSO (0.6–0.8%) gave a mean PCI value of 3.8% and range of 0.8–12.5% among genotypes. Media combining 2,4,5-T or 2,4-D with NAA in N6 medium also has reasonably good callus induction. For calli induced inside, 2,4-D (0.2–0.5 mg/l), NAA (2 mg/l) and KT (1 mg/l) contained media were superior. The maximum green plant regeneration (PPR) of 77.3% was found with the medium containing NAA 0.25 mg/l, IAA 0.5 mg/l and KT 2.0 mg/l. Significant genotype, medium and their interaction effects for per cent ovary survival and callus induction were observed.

Fire-Followers in Chaparral: Nitrogenous Compounds Trigger Seed Germination

1 Application of nitrates (optimal concentration c. 10mM) promoted seed germination in the fire annuals Emmenanthe penduliflora and Phacelia grandiflora and to a lesser extent in the fire-adapted shrub Salvia mellifera. Ammonium ions, although virtually inactive in E. penduliflora, were as effective as nitrate in both P. grandiflora and S. mellifera. 2 Diurnal illuminations and a chilling pretreatment, though of little effect by themselves, significantly enhanced the nitrate-mediated promotion of germination in the two fire annuals. 3 Nitrate was the principal factor inducing germination in E. penduliflora (nitrate or ammonium in P. grandiflora) whereas in S. mellifera light was the principal agent. It was also shown in E. penduliflora that nitrates are not required during chilling, i.e. seed sensitisation by chilling and nitrate-mediated induction of germination are entirely different mechanisms. 4 In the three species tested, the effect on seed germination caused by nitrogenous substances was nearly identical to that produced by an extract of charred wood, although chemical analysis of the extract showed that the combined concentrations of nitrates, ammonium ions and free amino acids could not account for the promotive action of charate. However, the nitrate and ammonium concentrations required to induce germination are very close to the increased values encountered after a fire in the otherwise nitrogen-poor chaparral soil. Therefore, in addition to the possible effect of charred wood, the postfire germination flush observed in chaparral may be induced by the increased levels of available nitrogen as well.

Germination Ecophysiology of Leymus cinereus (Poaceae)

We studied seed germination responses of 41 collections of Leymus cinereus (basin wildrye), a native perennial bunchgrass widely distributed in western North America. Collections made in 1987 and 1988 were largely nondormant in midautumn but relatively slow to germinate at optimal temperatures (mean germination time 6-16 d). Seeds germinated more quickly after a 2-wk chilling pretreatment (mean germination time 2-11 d). Mean germination time under conditions simulating prolonged snowpack (1⚬C) varied among collections from 6 to 12 wk and was negatively correlated with mean January temperature at the collection site. In dry-afterripening experiments with four 1992 collections, seeds showed only minor change in germination rate and percentage after time in dry storage, unlike seeds of Bromus tectorum (cheatgrass) and Elymus elymoides (squirreltail), which are facultatively fall-emerging. Field retrieval studies showed that L. cinereus seeds did not germinate in autumn even under conditions that triggered co...

Gibberellins in seeds of Arabidopsis thaliana: biological activities, identification and effects of light and chilling on endogenous levels

The activities of several gibberellins in stimulating germination of wild-type and GA-deficient gal seeds of Arabidopsis thaliana were compared. Of the six compounds tested GA4 and GA7-isolactone had the highest activity and GA7 and GA9 the lowest; activities of GA1 and GA3 were intermediate. Combined application of pure GAs presented no indications that more than one GA receptor is involved. Four GAs were identified in extracts from wild-type and GA-insensitive gai seeds by combined gas chromatography mass spectrometry: GA1, GA3, GA4 and GA9. Effects of light and chilling on levels of GA1, GA4 and GA9 were studied using deuterated standards. Light increased both GA levels and germination in unchilled wild-type and gai seeds. As a result of irradiation GA levels in gai seeds were 7–10 times as high as in wild-type seeds. In the dark germination was 0%, in the light 14% of gai seeds and 95% of wild-type seeds germinated. A chilling pre-treatment of 7 days at 2°C was required to enhance further the germination of gai seeds in the light. Light did not increase GA levels of chilled seeds of either genotype; levels of GA4 and GA9 of chilled gai seeds, in the light were respectively 7 and 12 times lower than in non-chilled seeds, whereas the latter seeds germinated better. Slightly elevated levels of GA4 were detected in darkness after chilling, but germination capacity was still 0%. These results strengthened the conclusion that GAs are required for germination of A. thaliana seeds, whereby GA4 has intrinsic biological activity. However, it is unlikely that light and chilling stimulate germination primarily by increasing levels of GA. Instead GA sensitivity is a possible alternative.

Photooxidative inhibition of nitrate reductase during chilling

The effect of a temperature close to the freezing point (chilling) on the nitrate reductase system of leaf discs of Cucumis sativus L. cv. Kleine Groene Scherpe was determined in the absence and presence of light. The capacity of leaf discs in the light (250 μE m−2s−1) at 20°C to increase in vivo and in vitro nitrate reductase activity, was unaffected by chilling pretreatment in the dark, but 4 h of chilling pretreatment in the light (250 μE m−2s−1) decreased the capacity to less than 50% of the unchilled control. The chilling inhibition of the capacity to increase nitrate reductase activity was of a photooxidative nature since it only occurred in the presence of light and oxygen. Plants grown at a low light intensity (65 μE m−2s−1) lost 95% of their capacity to increase nitrate reductase activity, while plants grown at 195 μE m−2s−1 retained 80% of their nitrate reducing capacity after 6 h chilling pretreatment in the 250 μE m−2s−1 light. Previously induced nitrate reductase activity was also affected by light during chilling. A lag phase of 7 h preceded a fast phase of decrease in activity. Both in vivo and in vitro activity decreased to 15% of the control value after 18 h of chilling in the light. It is concluded that the induction mechanism of nitrate reductase is primarily affected by photooxidation during chilling. The decrease in nitrate reductase activity is attributed to a decrease in the amount of activity enzyme.

Effects of Chilling, Anther Preculture and Growth Regulators on Embryogenesis in Isolated Pollen Culture of Nicotiana rustica L.

Pollen culture of Nicotiana rustica was performed by using 3 tages of pollen as the experimeutal materials. Freshly isolated pollen failed to form embryoid regardless of the presence of NAA and BA. Embryoids were produced from pollen isolated from anthers precultured on agar medium for 4 days or liberated. from anthers floated on liquid medium for 6 days. Prolonged preculture, however, reduced embryoid formation in both methods. Presence of NAA and BA in the media inhibited the induction of embryogenesis even at extremely low concentrations. Chilling pretreatment of flower buds at 5°C for 4 days remarkably increased embryoid formation. The inhibitory effect of prolonged preculture on liquid medium medium was cancelled by the chilling pretreatment, but not the case in the preculture on agar medium. By using the method with preculture on liquid medium, embryoid formation occurred in both uninucleate and mitotic stages but not in the early binucleate stage where high androgenic response, although, was observed in anther culture.

Effect of cambial dormancy state on the transport of [1-14C]indol-3-ylacetic acid in Abies balsamea shoots

Dormant attached or detached shoots of balsam fir were naturally or artificially chilled to induce different states along the rest–quiescence continuum. At the end of the chilling pretreatment, the shoots either were left intact or were debudded and treated with indol-3-ylacetic acid (IAA). The shoots were placed under controlled-environment conditions favorable for growth, and at intervals thereafter, a pulse of [1-14C]IAA was applied to the shoot apex. Measured at the end of the chilling pretreatment, [14C]IAA velocity and flux decreased with increasing duration of chilling (i.e., as rest graded into quiescence). The time required to commence cambial growth and to attain maximum rates of cambial activity and [14C]IAA transport also decreased as rest changed to quiescence. Transport in actively growing shoots exceeded that in quiescent shoots, but was similar to that in resting shoots. The [14C]IAA pulse moved basipetally as unchanged IAA, was blocked by a bark + cambium girdle, and was inhibited by abscisic acid and long-term application of exogenous IAA. The results indicate that: (1) the long-distance, cambium-located, IAA transport system demonstrated in dicotyledonous species also operates in conifers, (2) during the dormant period changes occur in [14C]IAA transport and in the cambial response to exogenous IAA, (3) the change in [14C]IAA transport is the result of change in the transporting capability of cells in the cambial zone, and (4) the change in [14C]IAA transport is not the cause of the differential response of quiescent and resting cambia to exogenous IAA.

Photooxidative damage to the photosynthetic apparatus during chilling

AbstractShort periods of chilling in the presence of light (up to 6 h: 1°C; 270 W/m2) decreased the subsequent apparent photosynthesis and chlorophyll fluorescence of leaf discs of Cucumis sativus L. cv. Kleine Groene Scherpe. The extent of the injury depended on the duration of the chilling pretreatment. After 6 h the subsequent apparent photosynthesis even reached a negative value, and it increased only slightly during the next 2 1/2 h. The decrease of apparent photosynthesis was not a consequence of increased dark respiration but was of photooxidative origin since the presence of both light and oxygen was required. Preincubation in the light for 2 h at 20°C sensitized leaf discs to subsequent photooxidation during chilling. Prompt and delayed chlorophyll fluorescence decreased simultaneously after chilling and light treatment. The corresponding decrease of photosynthesis and chlorophyll fluorescence is discussed in relation to primary photooxidative damage to the photosystems in the chloroplast membrane.