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In this study we investigated the interaction between temperature and genotype on fruit development and levels of total phenols and anthocyanins in cloudberry. The experiment was done in a phytotron using one female (‘Fjellgull') and one hermaphroditic (‘Nyby') cultivar. Plants were grown at 9, 12, 15 and 18°C in 24-h photoperiod. The female cultivars were pollinated with pollen from a male (‘Apollen') clone and from the hermaphrodite clone. Parthenocarpic fruit development was induced by gibberellic acid (GA3). Ripe berries were frozen individually at -80°C and stored until analyses. There was a linear, double logarithmic relationship between temperature and number of days from pollination/GA3-treatment to ripening. ‘Fjellgull' had significantly larger berries than ‘Nyby', and the largest berries were obtained at 12 and 9°C. Pollen clone did not have a significant effect on berry size. GA3induced parthenogenesis in ‘Fjellgull' and partial parthenogenesis in ‘Nyby'. In ‘Fjellgull', the parthenocarpic berries were comparable to pollinated ones at low temperatures, but at 18°C their development was restricted. The level of total anthocyanins was significantly higher in ‘Fjellgull' than in ‘Nyby', and these levels were significantly enhanced at 9 and 12°C compared to higher temperatures. Levels of total phenolic compounds were not significantly affected. In conclusion, the present results indicate that low temperature is favourable both for size and quality of cloudberries.

In this study we investigated the interaction between temperature and genotype on fruit development and levels of total phenols and anthocyanins in cloudberry. The experiment was done in a phytotron using one female (‘Fjellgull') and one hermaphroditic (‘Nyby') cultivar. Plants were grown at 9, 12, 15 and 18°C in 24-h photoperiod. The female cultivars were pollinated with pollen from a male (‘Apollen') clone and from the hermaphrodite clone. Parthenocarpic fruit development was induced by gibberellic acid (GA3). Ripe berries were frozen individually at −80°C and stored until analyses. There was a linear, double logarithmic relationship between temperature and number of days from pollination/GA3-treatment to ripening. ‘Fjellgull' had significantly larger berries than ‘Nyby', and the largest berries were obtained at 12 and 9°C. Pollen clone did not have a significant effect on berry size. GA3induced parthenogenesis in ‘Fjellgull' and partial parthenogenesis in ‘Nyby'. In ‘Fjellgull', the parthenocarpic berries were comparable to pollinated ones at low temperatures, but at 18°C their development was restricted. The level of total anthocyanins was significantly higher in ‘Fjellgull' than in ‘Nyby', and these levels were significantly enhanced at 9 and 12°C compared to higher temperatures. Levels of total phenolic compounds were not significantly affected. In conclusion, the present results indicate that low temperature is favourable both for size and quality of cloudberries.

Abstract: We have made and partially sequenced two subtracted cDNA libraries, one representing genes predominantly expressed in a tree from an early-flushing family of Norway spruce (early-flushing library; EFL) and the second from a late flushing family (late flushing library; LFL), during 4 weeks before bud burst. In the EFL, expressed sequence tags (ESTs) encoding proteins of the photosynthetic apparatus and energy metabolism and proteins related to stress (abiotic and biotic) and senescence were abundant. ESTs encoding metallothionein-like and histone proteins as well as transcription factors were abundant in the LFL. We used quantitative real-time reverse transcription polymerase chain reaction to study the expression patterns of 25 chosen genes and observed that the highest levels of activity for most genes were present when plants were still ecodormant. The results indicate that the late flushing is not a result of a delay in gene activity, but is rather associated with an active transcriptional process. Accordingly, certain metabolic processes may be turned on in order to prevent premature flushing. We discuss the putative role of the studied genes in regulation of bud burst timing. Among the candidate genes found, the most interesting ones were the DNA-binding proteins, water-stress-related genes and metallothioneins. Expression patterns of some genes involved in chemical modification of DNA and histones indicate that epigenetic factors are involved in the timing of bud burst. In the obtained transcriptomes, we could not find genes commonly believed to be involved in dormancy and bud set regulation (PHY, CRY, ABI etc.) in angiosperm plants.

Plants of the fern Matteuccia struthiopteris from northern and southern populations in Norway were studied in a phytotron. Relative growth rate (RGR), growth period, and sporophyll production were measured under different photoperiod (12–24 h) day‐length and temperature (9–21 °C) treatments. For the southern plants, there were no significant differences between the different light treatments, but for the northern plants there was a significant (p<0.01) linear increase in the mean maximum RGR with increasing day‐length. Small, but statistically significant (p<0.01) differences were found between northern and southern plants when the mean maximum RGR‐values were compared. When plants from different origin were exposed to different treatment, there were major differences between the populations in the production of sporophylls (p<0.0001). Southern plants produced in average three times more sporophylls than the northern plants, and they had also higher proportions of fertile plants. Diurnal alternating temperature treatments gave no significant (p>0.05) effect on the mean maximum RGR compared with constant temperatures, but they gave significantly higher production of sporophylls. In general, the northern plants had a higher temperature threshold (approximately 12 °C) for sporophyll production than the southern plants (approximately 9 °C). Plants exposed to 24 h with natural light were generally more often fertile than plants exposed to a shorter photoperiod. The mean maximum RGR‐values and time needed to develop the fronds at the 9 °C treatment were fairly equal to those found under natural conditions close to the altitudinal distribution limit of M.struthiopteris in W Norway. In general, the investigation showed that the applied temperature and light treatments affected sporophyll production more than vegetative growth.

Abstract. Woody plants in the temperate and boreal zone undergo annual cycle of growth and dormancy under seasonal changes. Growth cessation and dormancy induction in autumn are prerequisites for the development of substantial cold hardiness in winter. During evolution, woody plants have developed different ecotypes that are closely adapted to the local climatic conditions. In this study, we employed distinct photoperiodic ecotypes of silver birch (Betula pendula Roth) to elucidate differences in these adaptive responses under seasonal changes. In all ecotypes, short day photoperiod (SD) initiated growth cessation and dormancy development, and induced cold acclimation. Subsequent low temperature (LT) exposure significantly enhanced freezing tolerance but removed bud dormancy. Our results suggested that dormancy and freezing tolerance might partially overlap under SD, but these two processes were regulated by different mechanisms and pathways under LT. Endogenous abscisic acid (ABA) levels were also altered under seasonal changes; the ABA level was low during the growing season, then increased in autumn, and decreased in winter. Compared with the southern ecotype, the northern ecotype was more responsive to seasonal changes, resulting in earlier growth cessation, cold acclimation and dormancy development in autumn, higher freezing tolerance and faster dormancy release in winter, and earlier bud flush and growth initiation in spring. In addition, although there was no significant ecotypic difference in ABA level during growing season, the rates and degrees of ABA alterations were different between the ecotypes in autumn and winter, and could be related to ecotypic differences in dormancy and freezing tolerance.

Temperate zone woody plants cold acclimate in response to both short daylength (SD) and low temperature (LT). We were able to show that these two environmental cues induce cold acclimation independently by comparing the wild type (WT) and the transgenic hybrid aspen (Populus tremula x Populus tremuloides Michx.) line 22 overexpressing the oat (Avena sativa) PHYTOCHROME A gene. Line 22 was not able to detect the SD and, consequently, did not stop growing in SD conditions. This resulted in an impaired freezing tolerance development under SD. In contrast, exposure to LT resulted in cold acclimation of line 22 to a degree comparable with the WT. In contrast to the WT, line 22 could not dehydrate the overwintering tissues or induce the production of dehydrins (DHN) under SD conditions. Furthermore, abscisic acid (ABA) content of the buds of line 22 were the same under SD and long daylength, whereas prolonged SD exposure decreased the ABA level in the WT. LT exposure resulted in a rapid accumulation of DHN in both the WT and line 22. Similarly, ABA content increased transiently in both the WT and line 22. Our results indicate that phytochrome A is involved in photoperiodic regulation of ABA and DHN levels, but at LT they are regulated by a different mechanism. Although SD and LT induce cold acclimation independently, ABA and DHN may play important roles in both modes of acclimation.

The main purpose of this study was to compare the effects of different doses of nitrate, ammonium and ammonium plus nitrate on frost hardiness in seedlings of white clover (Trifolium repens L.) and timothy (Phleum pratense L.). In addition, top growth of the plants was observed. Plants were grown under controlled conditions in a phytotron, fertilized with various levels of nitrogen and tested for freezing resistance after a hardening treatment at 6°C and 0.5°C. Soluble carbohydrates in the stolons of white clover were analysed using an-throne reaction and gas chromatography. Vegetative growth of timothy was almost equally enhanced by all three types of nitrogen fertilization, and the maximum growth was obtained at 8-16mM nitrogen. In white clover, the highest fresh and dry weight of the top was obtained with nitrate, followed by combined ammonium plus nitrate fertilization. White clover was sensitive to ammonium, and concentrations above 4 mM strongly inhibited growth. Frost resistance in timothy was reduced by nitrogen levels above 8 mM, more by ammonium than nitrate. Frost resistance in white clover was not affected significantly by nitrate but the highest level of ammonium nitrate (64 mM) partly prevented cold hardening. The sucrose content of white clover stolons increased in all treatments during hardening, and there was statistically significant positive correlation between sucrose content and the level of frost hardiness. Neither the glucose nor the pinitol content of stolons was affected by hardening.

Development of cold tolerance in white clover (Trifolium repens L.) genotypes originating from various parts of Norway and grown outdoors at Tromso, latitude 69°39'N, has been studied. Stolon samples for an artificial freezing test and for chemical analysis were collected three times during the autumn. Generally, the most northern genotypes were more cold tolerant than the southern ones. Cold tolerance increased significantly from September to November in all genotypes. Content of dry matter, soluble carbohydrates, sucrose and proline in stolons increased during the hardening process. These changes were similar in both northern and southern genotypes of white clover.

Gibberellins A19, A20, and A1 were applied to seedlings of birch (Betula pubescens Ehrh.) and alder (Alnus glutinosa (L.) Gaertn.) in order to test their ability to counteract growth inhibition induced by growth retardants (ancymidol and BX-112) or short day (SD, 12 h) photoperiod. Ancymidol inhibits early and BX-112 inhibits late steps in gibberellin biosynthesis. BX-112 inhibited stem elongation in both species while ancymidol, applied as a soil drench, was effective in alder only. Growth retardants affected stem elongation mainly by inhibiting elongation of internodes. All three gibberellins were equally active when applied to seedlings treated with ancymidol; however, only GA1 was able to counteract the growth inhibition induced by BX-112. SD-induced cessation of elongation growth in birch was counteracted by GA1, and to some degree, by GA20, while GA19 was inactive. SD treatment did not induce cessation of apical growth in alder. These results are consistent with the hypothesis that of gibberellins belonging to the early C-13 hydroxylation pathway, GA1 is the only active gibberellin for stem elongation.

Gibberellin A4 (GA4) is biologically active in Salix pentandra and is able to induce stem elongation in seedlings grown under short day (SD) conditions, as well as in seedlings grown under long day (LD) conditions and treated with a growth retardant BX-112. [3H2]GA4 and [2H2]GA4 were applied to seedlings and leaf and stem explants of S. pentandra, and metabolites were studied using HPLC and GC-MS. After application of [3H2]GA4 to seedlings of S. pentandra, one of the three main radioactive metabolites in the free acid fraction had retention properties similar to GA1. Using [2H2]GA4, this compound was identified by GC-MS with SIM as [2H2]GA1 both from short day-grown and BX-112-treated seedlings, as well as in leaf and stem explants. After injection of GA4 into a mature leaf, GA1 was mainly found in the elongating stem tissue. Thus, the possibility that the biological activity of GA4 in Salix is due to its conversion to GA1 cannot be excluded.

Vegetative growth of two ecotypes (lat. 78° 15'N and 69°37'N) of Salix polaris L. was studied in phytotron experiments. Dormancy of the winter buds was broken by chilling at 0.5°C for 14 to 42 days. Chilling requirement increased with decreasing growth temperature. The optimum temperature for bud break and shoot growth was about 15°C for both ecotypes. Cessation of apical shoot growth and abscission of shoot tip was not prevented by long photoperiods. However, at high temperature, 15°C or more, and in 18 to 24 h photoperiod, two or three growth flushes occurred frequently in both ecotypes. Leaf abscission in the arctic ecotype from lat. 78°N was not affected by photoperiod when grown at 6°C, but was stimulated by short photoperiod when grown at 15°C. In the ecotype from lat. 69°N leaf abscission was enhanced by short photoperiod even at 6°C.

Samples of 17 plant species (one herb, dwarf shrubs and trees) were collected monthly throughout the winter 1976/77. Samples were frozen down to selected temperatures and hardiness was estimated by visual observations of oxidative browning and bud break. In most species hardiness rapidly increased from September to November and dehardening started in February–March. In six species (Betula pubescens Ehrh., Picea abies (L.) Karst., Salix caprea L., Sorbus aucuparia L., Vaccinium myrtillus L., V. vitis-idaea L.) hardening developed faster at the continental than at the coastal location. Differences in maximum hardiness between sampling locations were generally small and there were no real differences in dehardening of the plants between the locations. Both twigs and buds of Salix pentandra L. and Populus tremula L. survived liquid nitrogen in January–February.

The main purpose of these studies was to investigate the adaptation of young seedlings of various seed lots of Picea abies (L.) Karst., P. glauca (Moench) Voss, P. x lutzii Little and P. sitchensis (Bong.) Carr. to northern climatic conditions. Effects of temperature and photoperiod on elongation growth and growth cessation were studied under controlled conditions in a phytotron. In addition, growth and survival of the seedlings outdoors at 69°39' N lat. were followed for two years. Seed lots of /'. abies originated from northern Norway (66° N lat.), those of the other species were from Alaska (between 57°.and 66° N lat.). The critical photoperiod for budset was 19-20 h for seed lots of P. abies. In general, the critical photoperiod for budset increased with increasing latitude of the seed source, but the results indicated a significantly shorter cirtical photoperiod for seed lots from about 60° N lat., <120 m a.s.l. of P. sitchensis (between 12 and 16 h) than for comparable seed lots of P x lutzii (17-18 h) or P. glauca (18 h). The time course of budset under natural light conditions, both in the phytotron and outdoors, generally followed the pattern predicted from the critical photoperiod. However, in P. glauca the budset occurred earlier than in P. abies although the latter had a longer critical photoperiod. Due to the short critical photoperiod and consequently delayed growth cessation and hardening, all seed lots of P. sitchensis (from 58° to 60° N lat.) were severely damaged during winter. Some damage was also observed in P. x lutzii and in P. abies. The optimum temperature for elongation growth was higher for P. sitchensis than for the other species. In the phytotron experiments, seedlings of P. sitchensis grew best at temperatures between 12 and 21°C, but at 9°C the best growth was obtained in some seed lots of P. abies. After two growth seasons outdoors, all seed lots of P. abies were taller than any seed lot of the other species. Also P. glauca seed lots and one seed lot of P. x lutzii showed good growth, and their growth rhythm seemed to be well adapted to the northern conditions.

Acclimation in seedlings and young plants of various ecotypes and crosses between ecotypes of Salix pentandra L. were studied under natural climatic conditions at 69°39' N lat. and in a phytotron. Rapid cold acclimation was initiated after cessation of apical growth and outdoors it occurred about four weeks earlier in a northern (from 69°39' N lat.) than in a southern (from 59°40'N lat.) ecotype. F1-populations from crosses between a northern and a southern ecotype gave an intermediate response. Experiments with different morphogenetic light treatments indicated that these treatments affected cold acclimation mainly through their effects on cessation of growth. There was, however, an indication that blue light, given during a daylength extension period, slightly prevented acclimation in seedlings of a northern ecotype. After budset cold hardening was effectively triggered by low temperatures (3°, -3°C), but also seedlings that were kept in short day conditions at a high temperature (12, 15°C) developed a significant level of frost hardiness (about -40°C) during a period of eight weeks.

Survival of temperate‐zone tree species under the normal summer‐winter cycle is dependent on proper timing of apical growth cessation and cold acclimatization. This timing is primarily based on the perception of daylength, and through evolution many tree species have developed photoperiodic ecotypes which are closely adapted to the local light conditions. The longest photoperiod inducing growth cessation, the critical photoperiod, is inherited as a quantitative character. The phytochrome pigment family is the probable receptor of daylength, but the exact role of phytochrome and the physiological basis for the different responses between photoperiodic ecotypes are not known. This report shows for the first time that over‐expression of the oat phytochrome A gene (PHYA) in a tree significantly changes the critical daylength and effectively prevents cold acclimatization. While the critical daylength for elongation growth in the wild‐type of hybrid aspen (Populus tremula × tremuloides) was approximately 15 h, transgenic lines with a strong expression of the oat PHYAgene did not stop growing even under a photoperiod of 6 h. Quantitative analysis of gibberellins (GA) as well as indole‐3‐acetic acid (IAA) revealed that levels of these were not down‐regulated under short days in the transgenic plants expressing high levels of oat PHYA, as in the wild‐type. These results indicate that photoperiodic responses in trees might be regulated by the amount of PHYAgene expressed in the plants, and that the amount of phytochrome A (phyA) affects the metabolism of GAs and IAA.

DRY seeds of several species survive exposure to extremely low temperatures, including immersion in liquid air for up to 60 d (refs 1–3), but most young seedlings are very susceptible4. Fully hardened twigs of several northern tree species tolerate freezing in liquid nitrogen (−196 °C) (ref. 5), and deep supercooling seems to be an important mechanism for the avoidance of freezing in both xylem ray parenchyma and flower buds of many other hardy but less cold resistant, deciduous, woody species6,7. Resistance to freezing stress in seeds has been suggested to be related to water content1,4,8, but little attention has been paid to either the relationship between stage of germination and degree of freezing resistance or the nature of the resistance. We report here that hydrated lettuce seeds (achenes) can avoid injury by deep supercooling and that the level of resistance can be determined precisely by differential thermal analysis (DTA). Furthermore, we show that the deep supercooling is dependent on the intact structure of the endosperm.

A novel type of abscission development, arrested abscission, is described for a rare variety of pubescent birch (Betula pubescens Ehrh. f. hibernifolia Ulvinen), the leaves of which dehydrate and remain attached to the plant. Anatomical examination of the abscission zone revealed that its development is temporally and spatially similar to that of normal leaves of Betula pubescens.Flooding and exogenous ethylene were effective in inducing shedding of the leaves at the beginning of the growing season, butthis effect was lost in senescing leaves. Leaf hydration and abscission were retained in the presence of external abscisic acid (ABA)in the non-abscising variety, which also had a lower level of endogenous ABA. The observed responses together with the alteredhormonal level in this variety suggest that apart from ethylene, ABA is involved in autumnal abscission indirectly by regulatingthe leaf water status.

Apical growth cessation in seedling progenies of three latitudinal ecotypes and ecotype crosses of Salix pentandra L. was investigated under controlled growth conditions and out-of-doors. The southern ecotype (59° 40′ N) was characterized by late growth cessation under short day conditions, short critical photoperiod for growth cessation, and high light sensitivity; the northern ecotype (69° 39′ N) by rapid growth cessation, long critical photoperiod, and low light sensitivity. The geographically intermediate ecotype (64° 28′ N) had an intermediate photoperiodic response. The hybrid progenies were, however, closer to the southern than to the northern parent ecotype indicating a tendency to favour inheritance of southern characters. Fluctuating temperatures (21 °C/9 °C and 18 °C/9 °C) induced growth cessation in the northern ecotype but not in the other ecotypes or ecotype crosses with the exception of a few plants of the intermediate ecotype and of two hybrid progenies. The time course of apical growth cessation in various progenies grown out-of-doors at 69° 39′ N was similar to that observed under SD conditions except that the differences between the northern ecotype and the other ecotypes and crosses were greater.

Germination inhibitors in methanol and water extracts of red beet fruits (Beta vulgaris cv. rubra L.) have been studied using lettuce and red beet seed germination as bioassays. The methanol extracts contained substances which inhibited lettuce seed germination, but had no effect on the germination of red beet seeds. Germination of both lettuce seeds and of water-leached or sulphuric acid-treated red beet seed balls were inhibited by the water extracts. The concentrations of ammonia, ferulic acid, and oxalate in the water extracts were much lower than required for inhibition of red beet seed germination. The water extracts contained, however, large amounts of inorganic ions, and the results clearly demonstrated that the inhibitory effect of the water extracts on red beet seed germination was mainly due to the content of such inorganic ions.