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Frost Tolerance (frost + tolerance)
Selected AbstractsFrost tolerance in excised leaves of the common bugle (Ajuga reptans L.) correlates positively with the concentrations of raffinose family oligosaccharides (RFOs)PLANT CELL & ENVIRONMENT, Issue 8 2009SHAUN PETERS ABSTRACT Mass increases in raffinose family oligosaccharides (RFOs, ,1,6-galactosyl extensions of sucrose) are well documented in the generative tissues of many plants upon cold acclimation, and they (i.e. mainly the two shortest RFO members, raffinose and stachyose) have been suggested as frost stress protectants. Our focus here was on the longer RFO members as they commonly occur in the frost-hardy evergreen labiate Ajuga reptans in its natural habitat, and accumulate to their highest concentrations in winter when the plant is faced with sub-zero temperatures. We examined the effects of RFO concentration and chain length on frost tolerance using excised leaves which accumulate long-chain RFOs under both cold and warm conditions, thereby uncoupling the acclimation temperature from RFO production. We demonstrated that frost tolerance in excised A. reptans leaves correlates positively with long-chain RFO accumulation under both acclimation temperatures. After 24 d post-excision in the warm, the leaves had increased their RFO concentrations (mainly long-chain RFOs) 22-fold to 78 mg g,1 fresh weight, and decreased their EL50 values (temperature at which 50% leakage occurred) from ,10.5 to ,24.5 °C, suggesting a protective role for these oligosaccharides in the natural frost tolerance of A. reptans. [source] The impact of cold temperatures during grain maturation on selected quality parameters of wheatJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 9 2007Maryke Craven Abstract The influence of sudden cold spells during grain filling of wheat on the quality traits of three South African hard red wheat cultivars (Gariep, Elands and Tugela-DN) was studied, with the emphasis on Hagberg falling number (HFN). Four treatments were used (,1 °C at soft dough stage, , 1 °C at late milk stage, , 4 °C at soft dough stage and , 4 °C at late milk stage) and were administered for one night only. From the results it was concluded that, although limited in duration, such frost conditions did have an effect on the quality of the wheat cultivars. Cultivars differed in their response to the various treatments but also as to what quality traits were affected the most. The , 4 °C at late milk stage resulted in significantly reduced HFN being measured for both Elands and Tugela-DN. A similar effect was observed for Gariep, but was not statistically significant. Although the response was limited to the main tillers only, the conclusion was made that it is probable that the reduced HFN would be visible in the pooled sample of head and side tillers. A screening protocol was suggested that would allow classification of cultivars for frost tolerance. Copyright © 2007 Society of Chemical Industry [source] Changes in abscisic acid, salicylic acid and phenylpropanoid concentrations during cold acclimation of androgenic forms of Festulolium (Festuca pratensis × Lolium multiflorum) in relation to resistance to pink snow mould (Microdochium nivale)PLANT BREEDING, Issue 4 2009E. Pociecha Abstract We investigated changes in concentrations of abscisic (ABA) and salicylic acid (SA), phenolic compounds and phenylalanine ammonia-lyase (PAL) activity in relation to cold-induced tolerance of four androgenic genotypes of Festulolium (Festuca × Lolium hybrids) to frost and to the snow mould fungus Microdochium nivale. Cold acclimation increased frost tolerance and resistance to snow mould. Resistant genotypes were characterized by higher ABA concentrations during the first 54 h of cold acclimation and lower concentrations of SA than susceptible genotypes. After cold acclimation, the content of phenolics was significantly lower in genotypes tolerant to frost and M. nivale infection than in susceptible genotypes, while PAL activity was significantly higher. Signalling networks controlling cold acclimation to frost (abiotic) and mould infection (biotic) appears to involve increases in foliar concentrations of ABA and decreases in the SA level during successful cold acclimation. Higher PAL activity and lower concentrations of phenolic compounds also appear to be associated with enhanced tolerance to frost and fungal attack. [source] Use of chlorophyll fluorescence to evaluate the cold acclimation and freezing tolerance of winter and spring oatsPLANT BREEDING, Issue 5 2001F. Rizza Abstract The efficiency of the excitation capture by open Photosystem II (PSII) reaction centres was measured by the Fv/Fm ratios in a collection of winter and spring oats in order to assess the effects of hardening and freezing on the functionality of PSII and also the suitability of a chlorophyll fluorescence-based method to screen oat cultivars for frost tolerance. A significant reversible decrease in Fv/Fm was found in all genotypes during acclimation to low, non-freezing temperatures. Fv/Fm analysis appears to be an attractive test for the evaluation of frost tolerance in oats, being rapid, non-invasive and capable of monitoring a trait related to a crucial stage in the acquisition of frost tolerance. It is more sensitive and precise than other standard methods and highly correlated with field-evaluated frost damage. The measurements made during recovery 1 or 2 days after stress when the visual symptoms are not yet expressed, were especially advantageous because of the large variability in genotype response. The r-values (close to 0.8) were reduced due to the non-standard behaviour of the winter cultivar ,Aintree'. The cold acclimation response of this genotype has been analysed in detail and the limits of artificial freezing tests are discussed. [source] Frost tolerance in excised leaves of the common bugle (Ajuga reptans L.) correlates positively with the concentrations of raffinose family oligosaccharides (RFOs)PLANT CELL & ENVIRONMENT, Issue 8 2009SHAUN PETERS ABSTRACT Mass increases in raffinose family oligosaccharides (RFOs, ,1,6-galactosyl extensions of sucrose) are well documented in the generative tissues of many plants upon cold acclimation, and they (i.e. mainly the two shortest RFO members, raffinose and stachyose) have been suggested as frost stress protectants. Our focus here was on the longer RFO members as they commonly occur in the frost-hardy evergreen labiate Ajuga reptans in its natural habitat, and accumulate to their highest concentrations in winter when the plant is faced with sub-zero temperatures. We examined the effects of RFO concentration and chain length on frost tolerance using excised leaves which accumulate long-chain RFOs under both cold and warm conditions, thereby uncoupling the acclimation temperature from RFO production. We demonstrated that frost tolerance in excised A. reptans leaves correlates positively with long-chain RFO accumulation under both acclimation temperatures. After 24 d post-excision in the warm, the leaves had increased their RFO concentrations (mainly long-chain RFOs) 22-fold to 78 mg g,1 fresh weight, and decreased their EL50 values (temperature at which 50% leakage occurred) from ,10.5 to ,24.5 °C, suggesting a protective role for these oligosaccharides in the natural frost tolerance of A. reptans. [source] The role of inorganic phosphate in the development of freezing tolerance and the acclimatization of photosynthesis to low temperature is revealed by the pho mutants of Arabidopsis thalianaTHE PLANT JOURNAL, Issue 3 2000Vaughan Hurry Summary Low temperature inhibits sucrose synthesis, leading to a phosphate-limitation of photosynthesis. We have used the Arabidopsis pho1-2 and pho2-1 mutants with decreased and increased shoot phosphate, respectively, to investigate whether low phosphate triggers cold acclimatization of photosynthetic carbon metabolism. Wild-type Arabidopsis, pho1-2 and pho2-1 were grown at 23°C and transferred to 5°C to investigate acclimatization in pre-existing leaves and in new leaves developing at 5°C. The development of frost tolerance and the accumulation of proline and sugars was unaltered or improved in pho1-2, and impaired in pho2-1. Sucrose phosphate synthase and cytoplasmic fructose-1,6-bisphosphatase activity and protein increase after transfer to 5°C. This increase was accentuated in pho1-2 and attenuated in pho2-1. RBCS and LHCB2 transcript levels decrease in pre-formed wild-type leaves after transfer to 5°C and recover in new leaves that develop at 5°C. The initial decrease was attenuated in pho1-2, and accentuated in pho2-1, where the recovery in new leaves was also suppressed. Rubisco activity increased in wild-type leaves that developed at 5°C. This increase was accentuated in pho1-2 and absent in pho2-1. NADP-glyceraldehyde-3-phosphate dehydrogenase, plastidic fructose-1,6-bisphosphatase and aldolase activity increase relative to phosphoglycerate kinase, transketolase and phosphoribulokinase in wild-type leaves at 5°C. This shift was accentuated in pho1-2 and reversed in pho2-1. Transcript levels for COR genes increase transiently 1 day after transfer to 5°C but were very low in leaves that developed at 5°C in wild-type Arabidopsis, pho1-2 and pho2-1. We conclude that low phosphate plays an important role in triggering cold acclimatization of leaves, leading in particular to an increase of Rubisco expression, changes in other Calvin cycle enzymes to minimize sequestration of phosphate in metabolites, and increased expression of sucrose biosynthesis enzymes. [source] | ||||||||||