Assessment and control of non‐indigenous brown bullhead Ameiurus nebulosus populations using fyke nets in shallow ponds

In order to evaluate fyke nets as a tool for population assessment and mass removal of brown bullhead Ameiurus nebulosus populations, small, shallow ponds were sampled during late summer in 1999 and 2000. Catch efficiency, species and size selectivity of fyke nets were investigated with the mark‐recapture method. Two different strategies were applied: (1) on six occasions, the mark‐recapture method was applied to entire populations, and (2) in six other cases, sampling was done in two replicated enclosed areas (625 m²). When applied to entire populations, fyke nets were found to be size selective, and capture efficiency significantly increased with standard length. Conversely, no size selectivity of fyke nets was found in enclosed areas. Sampling in replicated enclosures yielded reproducible estimates of population density and biomass. The results suggest that double fyke nets, when combined with the mark‐recapture technique, are a very useful tool for the efficient and reliable assessment of brown bullhead populations. The results of the study also suggest that double fyke nets may potentially be a cost‐effective tool for the mass removal of non‐indigenous brown bullhead populations.     

Relative contributions of photochemical and non-photochemical routes to excitation energy dissipation in rice and barley illuminated at a chilling temperature

The mechanistic basis for differential sensitivities to chilling-induced photoinhibition among two rice ( Oryza sativa L.) cultivars (an Indica and a Japonica type) and one barley cultivar ( Hordeum vulgare L. cv. Albori) was examined. When leaf segments were exposed to moderate illumination at 4°C, a sustained decrease in the photochemical efficiency of photosystem (PS) II measured as the ratio of variable to maximal fluorescence (F_v/F_m) was observed for several hours. An analysis of fluorescence quenching revealed a sudden drop in PSII-driven electron transport rate (ETR) and a rapid rise in the reduction state of the primary electron acceptor Q_A upon exposure to chilling in moderate light. There was no appreciable difference in the level of non-photochemical quenching (NPQ) nor in the xanthophyll cycle activity between Japonica rice and barley. However, barley was capable of sustaining a higher ETR, thereby keeping a lower reduction state of Q_A throughout the chilling for 6 h. The Indica rice was characterized by the lowest ability to develop the xanthophyll cycle-associated NPQ, particularly the fast relaxing NPQ component (qf), accompanied by the highest reduction state of Q_A and photoinhibitory quenching (qI). It is concluded that the lower susceptibility of barley to chilling-induced photoinhibition than Japonica rice is attributable to its higher potential to dissipate excess light energy via a photochemical mechanism, whereas Indica rice is more sensitive to photoinhibition at a chilling temperature than Japonica rice, due primarily to its lower capacity to develop an efficient NPQ pathway.     

Photoinhibition and recovery of photosynthesis in intact barley leaves at 5 and 20°C

Photoinhibition of photosynthesis and its recovery were studied in intact barley ( Hordeum vuigare L. cv. Gunilla) leaves grown in a controlled environment by exposing them to two temperatures, 5 and 20°C, and a range of photon flux densities in excess of that during growth. Additionally, photoinhibtion was examined in the presence of chloramphenicol (CAP, an inhibitor of chloroplast protein synthesis) and of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). Susceptibility to photoinhibition was much higher at 5 than at 20°C. Furthermore, at 20°C. CAP exacerbated photoinhibition strongly, whereas CAP had little additional effect (10%) at 5°C. These results support the model that net photoinhibition is the difference between the inactivation and repair of photosystem II (PSII); i.e. the degradation and synthesis of the reaction centre protein, Dl. Furthermore, the steady-state extent of photoinhibition was strongly dependent on temperature and the results indicated this was manifested through the effects of temperature on the repair process of PSII. We propose that the continuous repair of PS II at 20°C conferred at least some protection from photoinhibition. At 5°C the repair process was largely inhibited, with increased photoinhibition as a consequence. However, we suggest where repair is inhibited by low temperature, some protection is alternatively conferred by the photoinhibited reaction centres. Providing they are not degraded, such centres could still dissipate excitation energy non-radiatively, thereby conferring protection of remaining photochemically active centres under steady-state conditions.
A fraction of PS II centres were capable of resisting photoinhibition when the repair process was inhibited by CAP. This is discussed in relation to PS II heterogeneity. Furthermore, the repair process was not apparently activated within 3 h when barley leaves were transferred to photoinhibitory light conditions at 20°C.     

The relationship between changes in the redox state of plastoquinone and control of excitation energy distribution in photosynthesis

The hypothesis that excitation energy distribution between PS I and PS II is controlled by the redox state of the plastoquinone pool between the two photosystems was investigated using the green alga Chlorella vulgaris. Changes in the redox state of the pool were monitored by measurement of the area above the fluorescence induction curve on exposure to high-intensity light. In agreement with the hypothesis, exposure of state I adapted cells to light preferentially absorbed by PS II led to a reduction of the plastoquinone pool whilst exposure of State II adapted cells to light preferentially absorbed by PS I resulted in its oxidation. However, the limits within which these fluctuations occurred were much narrower than anticipated. The reasons for this are discussed in terms of the possible involvement of changes in the redox state of more specialised molecules associated with the main plastoquinone pool and the postulated role of plastoquinone as an electron shuttle between the two photosystems.     

Effects of heat and high irradiance stress on energy dissipation of photosystem II in low irradiance-adapted peanut leaves

To increase crop yields and not to compete for land with food crops, intercropping agricultural cultivation approach was introduced into cultivation of peanut (Arachis hypogaca L.). This approach improves the total yield of the crop per unit area, but decreases the yield of a single crop compared with mono-cropped agricultural cultivation approach. In wheat-peanut relay intercropping system, peanut plants would suffer heat and high light (HI) stress after wheat harvest. In the present work, peanut seedlings were cultivated in low light to simulate wheat-peanut relay intercropping environments. Upon exposure to heat and HI stress, energy dissipation in PSII complexes was evaluated by comparing those cultivated in low irradiance conditions with the mono-cropped peanut. The maximal photochemical efficiency of PSII (F_v/F_m) and the net photosynthetic rate (P_n) decreased markedly in relay-cropped peanut (RP) after heat and HI stress, accompanied by higher degree of PSII reaction center closure (1–qP). After heat and HI stress, higher antioxidant enzyme activity and less ROS accumulation were observed in mono-cropped peanut (MP) seedlings. Meanwhile, higher content of D1 protein and higher ratio of (A + Z)/(V + A + Z) were also detected in MP plants under such stress. These results implied that heat and HI stress could induce photoinhibition of PSII reaction centers in peanut seedlings and both xanthophyll cycle-dependent thermal energy dissipation and the antioxidant system were down-regulated in RP compared to classical monocropping systems after heat and high irradiance stress.     

Effect of light on abscisic acid‐induced proline accumulation in leaves: comparison between barley and wheat

Light enhanced the abscisic acid‐induced accumulation of proline in barley ( Hordeum vulgare L. cv. Georgie) and wheat ( Triticum durum L. cv. Valnova). In wheat ABA is ineffective in the dark. In both barley and wheat, the accumulation of proline in the light showed the same characteristics as those of the process that occurs in barley in the dark, namely a synergistic interaction between the hormone and K(Na)Cl, an enhancing effect of Cl⁻ anion in excess over K⁺ cation in the incubation medium, and an inhibiting effect of D ‐mannose and monensine. In wheat, furthermore, light is needed during treatment with ABA if proline is to accumulate. Light was effective in both wheat and barley during the second or accumulation phase of the hormonal process, whereas the events occurring in the first (or lag) phase did not require light. The results suggest that in wheat light induces a putative factor(s) involved in the proline accumulation pathway that is lost in the dark, whereas in barley it is present in the dark.     

Reversible effects of moderately elevated temperature on the distribution of excitation energy between the two photosystems of photosynthesis in intact avocado leaves

Initial (F_o), maximum (F_m) and steady-state (F_s) levels of modulated chlorophyll fluorescence were measured in intact avocado leaves (Persea americana Mill.) during state 1-state 2 transitions using a combination of modulated and non-modulated lights with synchronized detection. Under normal temperature conditions (20°C), transition from state 2 to state 1 was associated with a substantial increase (about 20%) in F_m and F_o whereas the F_m/F_o ratio remained constant, reflecting increased absorption cross-section of PS II. On the contrary, at moderately elevated temperature (35°C), these fluorescence changes were very limited, indicating marked inhibition of the state regulation. The fraction of light distributed to PS II () was calculated from the F_o, F_m and F_s levels for both types of leaves. In control leaves, varied from 48% (in state 2) to values as high as 58% (in state 1). In contrast, mild heat treatment resulted in values close to 50% in both states, indicating the inability of heated leaves to reach extreme state 1. The results suggested that avocado leaves under moderately elevated temperature conditions are blocked in a state close to state 2. This effect was shown to occur in a non-injurious temperature range (as shown by the preservation of the (photoacoustically monitored) oxygen evolution activity) and to be rapidly reversed upon lowering of the temperature. Thermally induced development of state 2 (independent on the light spectral quality) could possibly be a protective mechanism to avoid photodamage of the heat-labile PS II by high light intensities which usually accompany heat stress in the field.     

A comparative study on carbohydrate reserves and ethanolic fermentation in the roots of two wetland and non‐wetland species after commencement of hypoxia

The problem of availability of storage carbohydrates (fructans and starch) in oxygen‐deficient roots was investigated in wetland species ( Senecio aquaticus Hill., Myosotis palustris [L.] L. Em. Rchb.) and compared with related non‐wetland species ( Senecio jacobaea L., Myosotis arvensis [L.] Hill.) with respect to ethanolic fermentation (PDC activity, ethanol production).
In response to 24 h of hypoxic treatment, the pyruvate decarboxylase (PDC) activity in roots increased 4‐fold in M. arvensis and S. jacobaea , 2‐fold in S. aquaticus and only slightly in M. palustris . The rise in PDC activity was accompanied by an increase in ethanol content in the roots. The increase in ethanolic fermentation in roots of intact plants was associated with a slight increase in fructose and glucose and in a clear rise in sucrose content during the first 24‐48 h after commencement of the hypoxic treatment. Following 24 h of hypoxia, the content of fructans started to increase significantly for the duration of the experiment (9 days) in the four species. Since starch content changed only slightly during this period, the fructan:starch ratio increased under low energy availability. In the roots of flooding‐tolerant Senecio aquaticus , the ratio shifted most clearly from 2:1 in normoxia to 9:1 in hypoxia. For the roots of the two wetland species investigated, the results indicate a stronger accumulation of carbohydrates accompanied by a lower increase in PDC activity under root hypoxia, when compared with the related non‐wetland species respectively.     

Effect of jasmonic acid on the stomatal and nonstomatal limitation of leaf photosynthesis in barley leaves

The effect of long-term (7 days) and shortterm (up to 2 h) treatment of barley plants with jasmonic acid (JA) on the components contributing to stomatal and nonstomatal limitation of photosynthesis was studied. Net CO₂ assimilation rate (A) responses to intercellular CO₂ concentration (C _i ), i.e., A/C _i curves, were used to assess the photosynthetic ability. Long-term treatment of barley plants with JA led to a noticeable decrease in both the initial slope of the A/C _i curves and the maximum A at saturating C _i . The proportion of stomatal and nonstomatal factors in limitation of photosynthesis depended on the applied JA concentration. Short-term treatment with JA affected neither the stomatal conductivity for CO₂ nor the rate of photosynthetic CO₂ assimilation. We suggest that JA may affect photosynthesis indirectly, either as a stress-modulating substance, or through the alterations in gene expression.     

Light‐independent thermoluminescence from thylakoids of greening barley leaves. Evidence for involvement of oxygen radicals and free chlorophyll

A study was conducted to identify biophysical markers which change in response to changing chlorophyll organization during plant development. When heated to around 70°C in the dark, barley thylakoids emit red thermoluminescence (TL). This is a pure chemiluminescence signal and distinct from the lower-temperature TL bands of thylakoids that are seen only with preillumination. The development of the light-independent, 70°C TL band was investigated following transfer of dark-grown barley leaves to the light. Because of the rapidly increasing chlorophyll content of the plastid membrane, the TL signal was normalized against either chlorophyll or tissue mass of the starting material. In either case, the extent of the TL signal reached a maximum in the early hours of greening and then declined. The drop in signal over 20 h was approximately 50% for TL per unit tissue mass, and well over 90% for TL per unit chlorophyll. Exposure of plastid membrane samples to hydrogen peroxide for several minutes caused a large increase in light-independent TL, while addition of ascorbate caused substantial quenching. The fluorescence profiles of dark-grown barley leaves were recorded following transfer to the light. Basal fluorescence (F₀) reaches a substantial level after just seconds of illumination. Over the next few hours, F₀ increases only slightly and then starts to decline. The decline in F₀ is correlated with an increase in variable fluorescence (F_v) which indicates the appearance of active photosystem II. It is concluded that the early peak in F₀ reflects a state in which the leaves contain a maximum amount of disorganized chlorophyll. Considering the TL and fluorescence data together, we propose the following: When chlorophyll first appears in the system, it is not properly assembled into the complexes that offer photochemical or non-photochemical quenching of the excited state. Thus, fluorescence and parallel chlorophyll triplet formation are prevalent. The triplets cause generation of active oxygen resulting in lipid peroxidation and/or other radical-generating processes. When the membranes are heated, increased interaction of the radicals with chlorophyll generates chemiluminescence. We thus conclude that light-independent thermoluminescence is a marker for actual damage arising from poor chlorophyll organization and propose that this parameter might be usefully applied for assessing stress effects.     

CNS thermosensitivity and control of latent heat dissipation in the pigeon

Thermoregulatory responses to heat exposure were studied in 12 hand-reared, acclimated pigeons (Columbia livia). Measurements of body temperature (Tcl), brain temperature (Tbr), cutaneous water evaporation (CWE) and respiratory frequency (fr) were carried out in intact conscious heat exposed birds. In a second group of lightly restrained birds, fr and CWE were taken when temperatures of the trunk, brain and air (Ta) were independently changed. Increasing Tbr to 43.5–43.8°C induced a pronounced polypnea (deep and fast, (300 breaths min⁻¹) when Tcl regulated at 42.4°C. Moreover, when hyperthermia (Tcl = 43.0°C) was combined with increased Tbr (43.0–43.8°C) shallow and fast panting (>500 breaths min⁻¹) was evoked. CWE was probably elicited by inputs generated by the skin warm receptors as a result of increased Ta. Moreover it was demonstrated that warming the brain to 42.5°C elicits cutaneous water evaporation in birds exposed to 26°C. When a high Ta (60°C) is accompanied by a high relative humidity (17%), the combined effect generates inputs eliciting intensive panting. The integration of the present and earlier data allows us to generate a model demonstrating the distinguished significance of the trunk, skin and brain thermosensors in the regulation of both respiratory and cutaneous latent heat dissipation. The present model also emphasizes the fact that the highly thermosensitive pigeon brain responds in a similar pattern to that found in mammals     

Evaluation of biochemical methods for the non‐destructive identification of sex in upstream migrating salmon and sea trout

Female‐specific markers of reproductive activity [plasma 17β‐oestradiol (E2), vitellogenin (VTG) and alkali‐labile phosphoprotein phosphorous (ALP)] were measured over 12 months in a captive population of brown trout Salmo trutta . During the early months of the reproductive season (February to May) and using the concentration of plasma E2 or plasma ALP as a marker for females the proportion of fish in which sex was misidentified was high (15–50%). The misidentification rate was considerably lower (1–8%) using plasma VTG. Preliminary evaluation of a commercial immunochromatographic VTG test system as a screen for the presence or absence of VTG in plasma from brown trout provided results that were consistent with those obtained from direct measurement of plasma VTG levels by enzyme‐linked immunosorbent assay (ELISA). These preliminary conclusions were verified by sampling upstream‐migrating anadromous brown trout, sea trout, and Atlantic salmon Salmo salar trapped over a 6 month period. Plasma E2 levels did not satisfactorily discriminate between male and female sea trout and Atlantic salmon. Plasma VTG levels in both species, however, were bimodally distributed and it was assumed that this divergence corresponded to male (plasma VTG levels <10 μg ml⁻¹) and female (plasma VTG levels >800 μg ml⁻¹) fishes. Plasma ALP provided a more accurate indication of sex in the wild Atlantic salmon and sea trout than was suggested by the pilot study on captive brown trout. The commercial immunochromatographic VTG test system provided results that were wholly consistent with the data obtained from the trapped fishes by direct measurement of plasma VTG.     

Dependence of photosynthesis and energy dissipation activity upon growth form and light environment during the winter

Two very distinctive responses of photosynthesis to winter conditions have been identified. Mesophytic species that continue to exhibit growth during the winter typically exhibit higher maximal rates of photosynthesis during the winter or when grown at lower temperatures compared to individuals examined during the summer or when grown at warmer temperatures. In contrast, sclerophytic evergreen species growing in sun-exposed sites typically exhibit lower maximal rates of photosynthesis in the winter compared to the summer. On the other hand, shaded individuals of those same sclerophytic evergreen species exhibit similar or higher maximal rates of photosynthesis in the winter compared to the summer. Employment of the xanthophyll cycle in photoprotective energy dissipation exhibits similar characteristics in the two groups of plants (mesophytes and shade leaves of sclerophytic evergreens) that exhibit upregulation of photosynthesis during the winter. In both, zeaxanthin + antheraxanthin (Z + A) are retained and PS II remains primed for energy dissipation only on nights with subfreezing temperatures, and this becomes rapidly reversed upon exposure to increased temperatures. In contrast, Z + A are retained and PS II remains primed for energy dissipation over prolonged periods during the winter in sun leaves of sclerophytic evergreen species, and requires days of warming to become fully reversed. The rapid disengagement of this energy dissipation process in the mesophytes and shade sclerophytes apparently permits a rapid return to efficient photosynthesis and increased activity on warmer days during the winter. This may be associated with a decreasing opportunity for photosynthesis in source leaves relative to the demand for photosynthesis in the plant's sinks. In contrast, the sun-exposed sclerophytes – with a relatively high source to sink ratio – maintain PS II in a state primed for high levels of energy dissipation activity throughout much of the winter. Independent of whether photosynthesis was up- or downregulated, all species under all conditions exhibited higher levels of soluble carbohydrates during the winter compared to the summer. Thus downregulation of photosynthesis and of Photosystem II do not appear to limit carbohydrate accumulation under winter conditions. A possible signal communicating an altered source/sink balance, or that may be influencing the engagement of Z + A in energy dissipation, is phosphorylation of thylakoid proteins such as D1.This revised version was published online in October 2005 with corrections to the Cover Date.     

Response of antioxidant enzymes to transfer from elevated carbon dioxide to air and ozone fumigation, in the leaves and roots of wild‐type and a catalase‐deficient mutant of barley

A catalase-deficient mutant (RPr 79/4) and the wild-type (cv. Maris Mink) barley (Hordeum vulgare L.) counterpart, were grown for 3 weeks in high CO₂ (0.7%) and then transferred to air and ozone (120 nl 1^?1) in the light and shade for a period of 4 days. Leaves and roots were analysed for catalase (CAT, EC 1.11.1.6), superoxide dismutase (SOD, EC 1.15.1.1) and glutathione reductase (GR, EC 1.6.4.2) activities. CAT activity in the leaves of the RPr 79/4 catalase-deficient mutant was around 5-10% of that determined in Maris Mink, but in the roots, both genotypes contained approximately the same levels of activity. CAT activity in Maris Mink increased in the leaves after transferring plants from 0.7% CO₂ to air or ozone, reaching a maximum of 5-fold, after 4 days in shade and ozone. For the catalase-deficient mutant, only small increases in CAT activity were observed in light/air and light/ozone treatments. In the roots, CAT activity decreased consistently in both genotypes, after plants were transferred from 0.7% CO₂. The total soluble SOD activity in the leaves and roots of both genotypes increased after plants were transferred from 0.7% CO₂. The analysis of SOD isolated from leaves following non-denaturing PAGE, revealed the presence of up to eight SOD isoenzymes classified as Mn-SOD or Cu/Zn-SODs; Fe-SOD was not detected. Significant changes in Mn- and Cu/Zn-SOD isoenzymes were observed; however, they could not account for the increase in total SOD activity. In leaves, GR activity also increased in Maris Mink and RPr 79/4, following transfer from 0.7% CO₂; however, no constant pattern could be established, while in roots, GR activity was reduced after 4 days of the treatments. The data suggest that elevated CO₂ decreases oxidative stress in barley leaves and that soluble CAT and SOD activities increased rapidly after plants were transferred from elevated CO₂, irrespective of the treatment (light, shade, air or ozone).     

Zeaxanthin and non‐photochemical quenching in sun and shade leaves of C3 and C4 plants

The relationships between non‐radiative energy dissipation and the carotenoid content, especially the xanthophyll cycle components, were studied in sun and shade leaves of several plants possessing C₃ ( Hedera helix and Laurus nobilis ) or C₄ ( Zea mays and Sorghum bicolor ) photosynthetic pathways. Sun‐shade acclimation caused marked changes in the organisation and function of photosynthetic apparatus, including significant variation in carotenoid content and composition. The contents of zanthophyll cycle pigments were higher in sun than in shade leaves in all species, but this difference was considerably greater in C₃ than in C₄ plants. The proportion of photoconvertible violaxanthin, that is the amount of violaxanthin (V) which can actually be de‐epoxidised to zeaxanthin, was much greater in sun than in shade leaves. The amount of photoconvertible V was always linearly dependent on the chlorophyll a/b ratio, although the slope of the relationship varied especially between C₃ and C₄ species. The leaf zeaxanthin and antheraxanthin contents were correlated with non‐radiative energy dissipation in all species under different light environments. These relationships were curvilinear and variable between sun and shade leaves and between C₃ and C₄ species. Hence, the dissipation of excess energy does not appear to be univocally dependent on zeaxanthin content and other photoprotective mechanisms may be involved under high irradiance stress. Such mechanisms appear largely variable between C₃ and C₄ species according to their photosynthetic characteristics.     

Effects of salt stress on photosynthesis,PSII photochemistry and thermal energy dissipation in leaves of two corn (<Emphasis Type="Italic">Zea mays</Emphasis> L.) varieties

The effect of four different NaCl concentrations (from 0 to 102 mM NaCl) on seedlings leaves of two corn (Zea mays L.) varieties (Aristo and Arper) was investigated through chlorophyll (Chl) a fluorescence parameters, photosynthesis, stomatal conductance, photosynthetic pigments concentration, tissue hydration and ionic accumulation. Salinity treatments showed a decrease in maximal efficiency of PSII photochemistry (F_v/F_m) in dark-adapted leaves. Moreover, the actual PSII efficiency (ϕ_PSII), photochemical quenching coefficient (q_p), proportion of PSII centers effectively reoxidized, and the fraction of light used in PSII photochemistry (%P) were also dropped with increasing salinity in light-adapted leaves. Reductions in these parameters were greater in Aristo than in Arper. The tissue hydration decreased in salt-treated leaves as did the photosynthesis, stomatal conductance (g _s) and photosynthetic pigments concentration essentially at 68 and 102 mM NaCl. In both varieties the reduction of photosynthesis was mainly due to stomatal closure and partially to PSII photoinhibition. The differences between the two varieties indicate that Aristo was more susceptible to salt-stress damage than Arper which revealed a moderate regulation of the leaf ionic accumulation.     

Homology modelling and molecular dynamics aided analysis of ligand complexes demonstrates functional properties of lipid‐transfer proteins encoded by the barley low‐temperature‐inducible gene family, blt4

The homology modelling technique was used to predict the tertiary structures of three members of the low-temperature-inducible barley vegetative shoot epidermal lipid-transfer protein (LTP) family, BLT4, on the basis of the X-ray crystallographically determined three-dimensional structure of a maize seedling LTP. Differences between the maize LTP and the BLT4 family include amino acid substitutions around the entrance and inside the predicted hydrophobic binding tunnels of these proteins. Because of the deletion of the loop region corresponding to Val60–Gly62 of the maize LTP from all three BLT4 LTPs, their internal hydrophobic tunnels are longer. Molecular dynamics modelling shows that BLT4.9 can accommodate hexadecanoic acid in its binding tunnel in similar conformation to the maize LTP. However, modelled cis,cis-9,12-octadecandienoic acid had a more favourable interaction with the BLT4.9 LTP than with the maize protein. Di-cis,cis-9,12-octadecandienoyl phosphatidylglycerol and di-cis,cis-9,12-octadecandienoyl phosphatidylcholine were modelled in the BLT4.9 structure with the fatty acyl group at position 1 embedded in the binding tunnel and the group at position 2 located on the solvent accessible surface of the protein. The results of the modelling suggest that the phospholipid headgroup can form hydrogen and salt bridges with polar and charged residues outside the binding tunnel and the exposed hydrocarbon chain interacts with hydrophobic amino acids on the surface. These results are consistent with the proposal that BLT4 LTPs have a lipid-transfer function associated with frost acclimation in barley.