Sucrose metabolism in spring and winter wheat in response to high irradiance, cold stress and cold acclimation

Effects of low‐temperature stress, cold acclimation and growth at high irradiance in a spring (Triticum aestivum L. cv. Katepwa) and a winter wheat (Triticum aestivum L. cv. Monopol) were examined in leaves and crowns with respect to the sucrose utilisation and carbon allocation. Light‐saturated and carbon dioxide (CO₂)‐saturated rates of CO₂ assimilation were decreased by 50% in cold‐stressed spring and winter wheat cultivars. Cold‐ or high light‐acclimated Katepwa spring wheat maintained light‐saturated rates of CO₂ assimilation comparable to those of control spring wheat. In contrast, cold‐ or high light‐acclimated winter wheat maintained higher light and CO₂‐saturated rates of CO₂ assimilation than non‐acclimated controls. In leaves, during either cold stress, cold acclimation or acclimation to high irradiance, the sucrose/starch ratio increased by 5‐ to 10‐fold and neutral invertase activity increased by 2‐ to 2.5‐fold in both the spring and the winter wheat. In contrast, Monopol winter wheat, but not Katepwa spring wheat, exhibited a 3‐fold increase in leaf sucrose phosphate synthase (SPS) activity, a 4‐fold increase in sucrose:sucrose fructosyl transferase activity and a 6.6‐fold increase in acid invertase upon cold acclimation. Although leaves of cold‐stressed and high light‐grown spring and winter wheat showed 2.3‐ to 7‐fold higher sucrose levels than controls, these plants exhibited a limited capacity to adjust either sucrose phosphate synthase or sucrose synthase activity (SS[s]). In addition, the acclimation to high light resulted in a 23–31% lower starch abundance and no changes at the level of fructan accumulation in leaves of either winter or spring wheat when compared with controls. However, high light‐acclimated winter wheat exhibited a 1.8‐fold higher neutral invertase activity and high light‐acclimated spring wheat exhibited an induction of SS(d) activity when compared with controls. Crowns of Monopol showed higher fructan accumulation than Katepwa upon cold and high light acclimation. We suggest that the differential adjustment of CO₂‐saturated rates of CO₂ assimilation upon cold acclimation in Monopol winter wheat, as compared with Katepwa spring wheat, is associated with the increased capacity of Monopol for sucrose utilisation through the biosynthesis of fructans in the leaves and subsequent export to the crowns. In contrast, the differential adjustment of CO₂‐saturated rates of CO₂ assimilation upon high light acclimation of Monopol appears to be associated with both increased fructan and starch accumulation in the crowns.     

The effects of phenotypic plasticity on photosynthetic performance in winter rye, winter wheat and Brassica napus

The contributions of phenotypic plasticity to photosynthetic performance in winter (cv Musketeer, cv Norstar) and spring (cv SR4A, cv Katepwa) rye (Secale cereale) and wheat (Triticum aestivum) cultivars grown at either 20°C [non‐acclimated (NA)] or 5°C [cold acclimated (CA)] were assessed. The 22–40% increase in light‐saturated rates of CO₂ assimilation in CA vs NA winter cereals were accounted for by phenotypic plasticity as indicated by the dwarf phenotype and increased specific leaf weight. However, phenotypic plasticity could not account for (1) the differential temperature sensitivity of CO₂ assimilation and photosynthetic electron transport, (2) the increased efficiency and light‐saturated rates of photosynthetic electron transport or (3) the decreased light sensitivity of excitation pressure and non‐photochemical quenching between NA and NA winter cultivars. Cold acclimation decreased photosynthetic performance of spring relative to winter cultivars. However, the differences in photosynthetic performances between CA winter and spring cultivars were dependent upon the basis on which photosynthetic performance was expressed. Overexpression of BNCBF17 in Brassica napus generally decreased the low temperature sensitivity (Q₁₀) of CO₂ assimilation and photosynthetic electron transport even though the latter had not been exposed to low temperature. Photosynthetic performance in wild type compared to the BNCBF17‐overexpressing transgenic B. napus indicated that CBFs/DREBs regulate not only freezing tolerance but also govern plant architecture, leaf anatomy and photosynthetic performance. The apparent positive and negative effects of cold acclimation on photosynthetic performance are discussed in terms of the apparent costs and benefits of phenotypic plasticity, winter survival and reproductive fitness.     

Cold resistance in Antarctic angiosperms

Deschampsia antarctica Desv. (Poaceae) and Colobanthus quitensis (Kunth) Bartl. (Cariophyllaceae) are the only two vascular plants that have colonized the Maritime Antarctic. The primary purpose of the present work was to determine cold resistance mechanisms in these two Antarctic plants. This was achieved by comparing thermal properties of leaves and the lethal freezing temperature to 50% of the tissue (LT50). The grass D. antarctica was able to tolerate freezing to a lower temperature than C. quitensis. The main freezing resistance mechanism for C. quitensis is supercooling. Thus, the grass is mainly a freezing‐tolerant species, while C. quitensis avoids freezing. D. antarctica cold acclimated; thus, reducing its LT50. C. quitensis showed little cold‐acclimation capacity. Because day length is highly variable in the Antarctic, the effect of day length on freezing tolerance, growth, various soluble carbohydrates, starch, and proline contents in leaves of D. antarctica growing in the laboratory under cold‐acclimation conditions was studied. During the cold‐acclimation treatment, the LT50 was lowered more effectively under long day (21/3 h light/dark) and medium day (16/8) light periods than under a short day period (8/16). The longer the day length treatment, the faster the growth rate for both acclimated and non‐acclimated plants. Similarly, the longer the day treatment during cold acclimation, the higher the sucrose content (up to 7‐fold with respect to non‐acclimated control values). Oligo and polyfructans accumulated significantly during cold acclimation only with the medium day length treatment. Oligofructans accounted for more than 80% of total fructans. The degrees of polymerization were mostly between 3 and 10. C. quitensis under cold acclimation accumulated a similar amount of sucrose than D. antarctica, but no fructans were detected. The suggestion that survival of Antarctic plants in the Antarctic could be at least partially explained by accumulation of these substances is discussed.     

Hydrogen peroxide pretreatment of roots enhanced oxidative stress response of tomato under cold stress

In the view of physiological role of H₂O₂, we investigated whether exogenous H₂O₂ application would affect short-term cold response of tomato and induce acclimation. Pretreatments were performed by immersing roots into 1 mM H₂O₂ solution for 1 h when transferring seedlings from seedling substrate to soil (acclimated group). Cold stress (3 °C for 16 h) caused significant reduction in relative water content (RWC) of control and non-acclimated (distilled water treated) groups when compared with unstressed plants. H₂O₂ promoted maintenance of relatively higher RWC under stress. Anthocyanin level in leaves of acclimated plants under cold stress was significantly higher than that of unstressed control and non-acclimated plants. Malondialdehyde (MDA) levels demonstrated low temperature induced oxidative damage to control and non-acclimated plants. MDA remained around unstressed conditions in acclimated plants, which demonstrate that H₂O₂ acclimation protected tissues against cold induced lipid peroxidation. H₂O₂ acclimation caused proline accumulation in roots under cold stress. Ascorbate peroxidase (APX) activity in roots of cold stressed and unstressed H₂O₂ acclimated plants increased when compared with control and non-acclimated plants, with highest increase in roots of acclimated plants under cold stress. CAT levels in roots of acclimated plants also increased, whereas levels remained unchanged in unstressed plants. Endogenous H₂O₂ levels significantly increased in roots of control and non-acclimated plants under cold stress. On the other hand, H₂O₂ content in roots of acclimated plants was significantly lower than control and non-acclimated plants under cold stress. The results presented here demonstrated that H₂O₂ significantly enhanced oxidative stress response by elevating the antioxidant status of tomato.     

Low temperature regulates sucrose-phosphate synthase activity in Colobanthus quitensis (Kunth) Bartl. by decreasing its sensitivity to Pi and increased activation by glucose-6-phosphate

Colobanthus quitensis (Kunth) Bartl. is widely distributed from Mexico to the Antarctic. C. quitensis is a freezing resistant species that accumulates sucrose in response to cold. We tested the hypothesis that low temperature modifies the kinetic properties of C. quitensis sucrose phosphate synthase (SPS) to increase its activity and ability to synthesize sucrose during cold acclimation. Cold acclimation caused a fourfold increment in sucrose concentration and a 100% increase in SPS activity, without changes in the level of SPS protein. Cold acclimation did not affect the optimal temperature and pH for SPS activity. However, it caused a tenfold increase in the inhibition constant (K _i) for inorganic phosphate (Pi) calculated as a function of fructose-6-phosphate (Fruc-6-P). SPS from cold acclimated plants also exhibited a higher reduction of its Michaelis constant (K _m) for glucose-6-phosphate (Gluc-6-P) with respect to non-acclimated plants. We suggest that the increase in C. quitensis SPS K _i for Pi and the increase in activation by Gluc-6-P in response to cold keep SPS activated, leading to high sucrose accumulation. This may be an important adaptation that allows efficient accumulation of sucrose during the harsh Antarctic summer.     

Enhancement of frost tolerance in olive shoots in vitro by cold acclimation and sucrose increase in the culture medium

The evaluation of frost tolerance in olive shoots in vitro has been successfully accomplished. The behavior of in vitro shoots at freezing temperatures was comparable to that of intact plants. Cold acclimation was found to increase frost tolerance in cv. Moraiolo and the LT₅₀ was about 4 °C lower compared to nonacclimated shoots. Damage in acclimated shoots occurred at –15 °C, whereas control shoots were damaged at –10 °C. Olive shoots were unable to withstand freezing temperatures of –20 °C, even when acclimated. The effects of sucrose were also determined. 6% (w/v) sucrose in the medium conferred the highest frost tolerance in both acclimated and nonacclimated plants.     

The influence of cold acclimation on antioxidative enzymes and antioxidants in sensitive and tolerant barley cultivars

In order to better understand the role of cold acclimation in alleviating freezing injury, two barley cultivars with different cold tolerance, i.e. a sensitive cv. Chumai 1 and a tolerant cv. Mo 103, were used. The freezing treatment increased leaf soluble protein content more in the tolerant cultivar than in the sensitive one. Cold acclimation increased H₂O₂ content of the two cultivars during freezing treatment, especially in Mo 103. Glutathione and ascorbate contents during freezing and recovery were significantly higher in cold-acclimated plants than in non-acclimated ones. Activities of peroxidase, ascorbate peroxidase and glutathione reductase were also higher in cold-acclimated plants than non-acclimated plants during freezing treatment. However, there was no significant difference between cold-acclimated plants and the control plants in catalase activity. It may be assumed that cold acclimation induced H₂O₂ production, which in turn enhanced activities of antioxidative enzymes and synthesis of antioxidants, resulting in alleviation of oxidative stress caused by freezing.     

Isolation and functional characterization of cold-regulated promoters, by digitally identifying peach fruit cold-induced genes from a large EST dataset

Background  

Cold acclimation is the process by which plants adapt to the low, non freezing temperatures that naturally occur during late autumn or early winter. This process enables the plants to resist the freezing temperatures of winter. Temperatures similar to those associated with cold acclimation are also used by the fruit industry to delay fruit ripening in peaches. However, peaches that are subjected to long periods of cold storage may develop chilling injury symptoms (woolliness and internal breakdown). In order to better understand the relationship between cold acclimation and chilling injury in peaches, we isolated and functionally characterized cold-regulated promoters from cold-inducible genes identified by digitally analyzing a large EST dataset.     

Hardening trumps acclimation in improving cold tolerance of Drosophila melanogaster larvae

Abstract Chill‐susceptible insects are able to improve their survival of acute cold exposure over both the short term (i.e. hardening at a relatively severe temperature) and longer term (i.e. acclimation responses at milder temperatures over a longer time frame). However, the mechanistic overlap of these responses is not clear. Four larval stages of four different strains of Drosophila melanogaster are used to test whether low temperature acclimation (10 °C for 48 h) improves the acute cold tolerance (LT₉₀, ～2 h) of larvae, and whether acclimated larvae still show hardening responses after brief exposures to nonlethal cold or heat, or a combination of the two. Acclimation results in increased cold tolerance in three of four strains, with variation among instars. However, if acclimation is followed by hardening pre‐treatments, there is no improvement in acute cold survival. It is concluded that short‐term thermal responses (e.g. hardening) may be of more ecological relevance to short‐lived life stages such as larvae, and that the mechanisms of low temperature hardening and acclimation in D. melanogaster may be antagonistic, rather than complementary.     

Predicting ecosystem carbon balance in a warming Arctic: the importance of long‐term thermal acclimation potential and inhibitory effects of light on respiration

The carbon balance of Arctic ecosystems is particularly sensitive to global environmental change. Leaf respiration (R), a temperature‐dependent key process in determining the carbon balance, is not well‐understood in Arctic plants. The potential for plants to acclimate to warmer conditions could strongly impact future global carbon balance. Two key unanswered questions are (1) whether short‐term temperature responses can predict long‐term respiratory responses to growth in elevated temperatures and (2) to what extent the constant daylight conditions of the Arctic growing season inhibit leaf respiration. In two dominant Arctic species E riophorum vaginatum (tussock grass) and B etula nana (woody shrub), we assessed the extent of respiratory inhibition in the light (R _L/R _D), respiratory response to short‐term temperature change, and respiratory acclimation to long‐term warming treatments. We found that R of both species is strongly inhibited by light (averaging 35% across all measurement temperatures). In E . vaginatum both R _L and R _D acclimated to the long‐term warming treatment, reducing the magnitude of respiratory response relative to the short‐term response to temperature increase. In B . nana, both R _L and R _D responded to short‐term temperature increase but showed no acclimation to the long‐term warming. The ability to predict plant respiratory response to global warming with short‐term temperature responses will depend on species‐specific acclimation potential and the differential response of R _L and R _D to temperature. With projected woody shrub encroachment in Arctic tundra and continued warming, changing species dominance between these two functional groups, may impact ecosystem respiratory response and carbon balance.     

冷驯化对异色瓢虫后代生长发育及适合度的影响

为明确冷驯化处理对异色瓢虫Harmonia axyridis后代生长发育及适合度的影响, 本研究通过两性生命表的制作, 在室内条件下调查了冷处理后其后代发育历期、 成虫产卵前期、 寿命和生殖力以及后代生命表参数。结果表明: 冷驯化使异色瓢虫后代卵的发育历期延长, 幼虫（1-4龄）和蛹的发育历期则缩短; 随着冷驯化时间的延长, 后代体长和体重增量均减小。且完成发育的后代成虫产卵前期延长, 寿命缩短, 生殖力下降。后代生命表参数内禀增长率（r）、 周限增长率（λ）、 净生殖率（R₀）和年龄特征存活率（l_x）均降低, 但是后代雌虫所占比例却升高。此外, 冷驯化类型对异色瓢虫后代生长发育的影响也不相同。经相同时间（5 d）的低温诱导, 变温诱导的后代成虫寿命比恒定低温诱导的长, 但是生殖力却低; 变温诱导的后代生命表参数（r, λ和R₀）均小于恒定低温诱导的, 但是l_x却高于恒定低温诱导的。结果说明, 异色瓢虫亲代经历冷驯化, 这种对低温的可塑性反应会延伸到下一代, 而且还能够影响后代的适合度, 这对其在低温下的存活和繁殖具有重要的意义。     

Cold Acclimation Ability and Photosynthesis among Species of the Tropical Coffea Genus

Abstract: Three Coffea species (C. arabica cv. Icatu, C. canephora cv. Apoatã and C. dewevrei) were tested in order to identify and study the mechanisms of tolerance to low, non‐freezing temperatures. Several photosynthesis‐related parameters were monitored during a 20‐day period of gradual temperature decrease, from 25/20 °C (day/night) down to 15/10 °C, during chilling treatments (15/4 °C), and upon rewarming (25/20 °C). Differences were found among species, both during low temperature exposure and during rewarming. In general, Coffea species showed cold‐induced photoinhibition of photosynthesis, which was attributable to biochemical (in vivo ribulose‐1,5‐bisphosphate carboxylase/oxygenase activity and carbohydrate synthesis) and biophysical (antennae functioning, photosystem II efficiency and linear electron transport) inactivation, rather than to stomatal constraints. The moderately low temperature of 15/10 °C was enough to cause a negative impact on net photosynthesis (A), mostly due to low (initial) rubisco activity in all species. However, C. arabica cv. Icatu showed a higher tolerance to chilling and recovered quickly and completely upon rewarming, as assessed from the impacts on the photosynthetic machinery (e.g. A_max, F_o, F_v/F_m, F_v′/F_m′, q_P, ?_e, rubisco activity) and on carbohydrate metabolism. Such lesser effects are likely to be related to the strong increases and higher contents of zeaxanthin, lutein and β‐carotene that presumably increased the ability to dissipate excitation energy and contributed to protect the photosynthetic apparatus. During cold exposure, a significant reduction of the α/β carotene ratio, which is considered an acclimation feature, was observed solely in C. arabica cv. Icatu. However, C. canephora cv. Apoatã and, especially, C. dewevrei showed to be highly cold‐sensitive. In these latter species, the photoinhibitory impairments to photosynthesis were stronger, probably due to the lower contents of protecting pigments during chilling conditions that lead to a higher vulnerability to excess excitation energy. Moreover, the mesophyll impairments (e.g. A_max, F_v/F_m, ?_e) became significant even at moderately low temperatures of 15/10 °C, and a lower ability to recover after chilling exposure was observed. The limitation of in vivo rubisco activity and A_max may have been due to substrate limitation, but disturbances in sugar metabolism could also play an important role in the expression of chilling sensitivity in C. canephora cv. Apoatã and C. dewevrei.     

Photosynthetic acclimation of Pinus taeda (loblolly pine) to long-term growth in elevated pCO2 (FACE)

Growth in elevated pCO₂ generally leads to a stimulation of net CO₂ uptake rate. However, with long‐term growth the magnitude of this stimulation is often reduced. This phenomenon, termed acclimation, has been largely attributed to a loss of Rubisco (ribulose 1,5 bisphosphate carboxylase). The mechanism by which Rubisco content declines with long‐term growth is not certain. There is evidence for a sugar‐mediated, selective down‐regulation of Rubisco protein and also for a non‐selective loss of total leaf nitrogen, which impacts Rubisco levels indirectly. Over a season, and including needles at different developmental stages, we investigated these two potential mechanisms in well‐developed Pinus taeda grown for approximately 2·5 years in elevated (56 Pa) pCO₂ using free air CO₂ enrichment technology. Photosynthetic acclimation, as manifested by a decrease in the activity of Rubisco measured both in vivo (? 25%, via gas exchange) and in vitro (? 35%, via enzyme assays), was observed with growth in elevated pCO₂. This acclimation was observed in one‐year‐old needles but not in current‐year needles. Needles exhibiting acclimation had reduced levels of Lsu Rubisco (? 25%) and an increased foliar carbohydrate content (+ 30%) but showed no evidence of a decrease in needle nitrogen or total protein content. These data support the concept that photosynthetic acclimation in elevated pCO₂ is caused by a selective down‐regulation of Rubisco.     

Contrasting responses of photosynthesis at low temperatures in different annual legume species

Growth, net photosynthetic rate (P _N), chlorophyll fluorescence induction kinetics, and stromal fructose-1,6-bisphosphatase (sFBPase) in annual legumes native to the Mediterranean region, two clovers (Trifolium subterraneum L. ssp. oxaloides Nyman cv. Clare and T. michelianum Savi cv. Giorgia) and two Medicago species (M. polymorpha L. cv. Anglona and M. truncatula Gaertn. cv. Paraggio), shifted from 20 to 10 °C for 1 d or developed at 10 °C were compared with controls kept at 20 °C. Cold development produced a larger stimulation of growth in the clover cv. Giorgia and the Medicago cv. Paraggio. Transferring plants to low temperatures affected P _N relatively less in clovers than in Medicago plants. Development at 10 °C relieved the inhibition of photosynthesis in Giorgia and Paraggio, but not in Clare and Anglona, which correlated with increases in the maximum rate of carboxylation by ribulose-1,5-bisphosphate carboxylase/oxygenase, RuBPCO (V_cmax), and the photon-saturated rate of electron transport (J_max). In Medicago, transfer from high to low temperature inhibited photosynthesis in a lesser extent in Anglona than in Paraggio, which showed severe limitations at level of V_cmax and J_max. Development at 10 °C in Paraggio produced an efficient photosynthetic cold acclimation, this being associated with a two-fold increase of quantum yield of photosystem 2 electron transport (F/F'_m) and with the activity of sFBPase. By contrast, Anglona showed an irreversible inhibition of P _N coupled with the reduction of carbon metabolism by impairment of Calvin cycle enzyme activities such as RuBPCO and sFBPase, resulting in a poor cold acclimation of photosynthesis in this cultivar.     

Source of nitrogen associated with recovery of relative growth rate in Arabidopsis thaliana acclimated to sustained cold treatment

To determine (1) whether acclimation of carbon metabolism to low temperatures results in recovery of the relative growth rate (RGR) of plants in the cold and (2) the source of N underpinning cold acclimation in Arabidopsis thaliana, we supplied plants with a nutrient solution labelled with ¹⁵N and subjected them to a temperature shift (from 23 to 5 °C). Whole‐plant RGR of cold‐treated plants was initially less than 30% of that of warm‐maintained control plants. After 14 d, new leaves with a cold‐acclimated phenotype emerged, with the RGR of cold‐treated plants increasing by 50%; there was an associated recovery of root RGR and doubling of the net assimilation rate (NAR). The development of new tissues in the cold was supported initially by re‐allocation of internal sources of N. In the longer term, the majority (80%) of N in the new leaves was derived from the external solution. Hence, both the nutrient status of the plant and the current availability of N from external sources are important in determining recovery of growth at low temperature. Collectively, our results reveal that both increased N use efficiency and increases in nitrogen content per se play a role in the recovery of carbon metabolism in the cold.     

Acclimation to low light by C4 maize: implications for bundle sheath leakiness

C4 plants have a biochemical carbon concentrating mechanism (CCM) that increases CO₂ concentration around ribulose bisphosphate carboxylase oxygenase (Rubisco) in the bundle sheath (BS). Under limiting light, the activity of the CCM generally decreases, causing an increase in leakiness, (Φ), the ratio of CO₂ retrodiffusing from the BS relative to C4 carboxylation processes. Maize plants were grown under high and low light regimes (respectively HL, 600 versus LL, 100 μE m^?2 s^?1). Short‐term acclimation of Φ was compared from isotopic discrimination (Δ), gas exchange and photochemistry. Direct measurement of respiration in the light, and ATP production rate (J_ATP), allowed us use a novel approach to derive Φ, compared with the conventional fitting of measured and predicted Δ. HL grown plants responded to decreasing light intensities with the well‐documented increase in Φ. Conversely, LL plants showed a constant Φ, which has not been observed previously. We explain the pattern by two contrasting acclimation strategies: HL plants maintained a high CCM activity at LL, resulting in high CO₂ overcycling and increased Φ; LL plants acclimated by down‐regulating the CCM, effectively optimizing scarce ATP supply. This surprising plasticity may limit the impact of Φ‐dependent carbon losses in leaves becoming shaded within developing canopies.     

Effects of Low Temperature on Winter Wheat and Cabbage Leaves

Contents of soluble proteins, proline and chlorophyll in winter wheat (Triticum aestivum cv. Doğu-88) and cabbage leaves (Brassica oleracea convar. acephala) during acclimation to low temperature were investigated. When both of the plants species were cold acclimated, soluble proteins, proline and chlorophyll contents were higher than in the controls (non-acclimated). Also protein patterns differed between the plants at control and cold conditions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Impact of soluble sugar concentrations on the acquisition of freezing tolerance in accessions of Arabidopsis thaliana with contrasting cold adaptation – evidence for a role of raffinose in cold acclimation

In the present study the cold acclimation potential of two accessions of Arabidopsis thaliana was investigated. Significant variation was found for basic tolerance as well as the capacity to acclimate to freezing temperatures. During cold acclimation, levels of soluble sugars increased in both genotypes, but raffinose accumulation discriminated the more tolerant accession Col‐0 from C24. Concentrations of other compatible solutes such as proline and glutamine were also higher in cold‐acclimated Col‐0 than C24 plants. Changes of invertase activity during cold exposure corresponded to changes in sucrose and fructose, but not glucose concentrations and were consistent with an initial chilling response and a later decline in hexose metabolization. When vacuolar invertase was suppressed by siRNA expression, reduced sucrolytic activity resulted in elevated leaf sucrose concentration, whereas the fructose content was strongly reduced. This led to elevated freezing tolerance in the cold‐tolerant genotype Col‐0, but not in C24. The most pronounced metabolic changes in invertase‐inhibited Col‐0 plants occurred for proline and glutamine concentrations, indicating indirect metabolic effects of altered sugar concentrations.     

Expression of dehydration-stress-related genes in the crowns of wheatgrass species [Lophopyrum elongatum (Host) A. Love and Agropyron desertorum (Fisch. ex Link.) Schult.] having contrasting acclimation to salt, cold and drought

Agropyron desertorum and Lophopyrum elongatum were grown in a control environment or acclimated in high‐salt (daily exposure to 75 or 150 m M NaCl for 6 d), cold (6/2 °C for 14 d) or drought environments (watering withheld for 6 d). Lophopyrum elongatum was constitutively tolerant to salt and also acclimated more to salt than did A. desertorum whereas A. desertorum acclimated more to cold and drought. Dehydrin and non‐specific lipid transfer protein (nsLTP) mRNA sequences and polypeptides increased more, during acclimation to cold and drought, in A. desertorum than in L. elongatum crowns. Expression of immunologically identified dehydrin polypeptides was much higher in drought‐acclimated A. desertorum than in any other species/treatment combination. The most strongly expressed were 42 and 20 kDa. No change in dehydrin or nsLTP polypeptides were detected in the crowns during acclimation to salt. Overall, there was stronger acclimation to dehydrative stresses, at the molecular level, in A. desertorum than in L. elongatum crowns. Differences in dehydrin and nsLTP mRNA and polypeptide expression during acclimation to different stresses indicated that plants sense the differences between different primary potential causes of cellular dehydration.