The Water Relations of Pinus sylvestris

The water potential (β) in ten-year-old Scots pine trees (Pinus sylvestris L.) from four different latitudinal provenances ranging from 57° N to 67° N, growing in close proximity to each other, was measured in a pressure chamber during five selected periods between May 1972 and March 1973. Diurnal and seasonal patterns of φ are presented in relation to irradiance, air temperature and vapour pressure deficit (D) for one cloudy and one clear day in each experimental period. The largest daily amplitude in φ was found at the beginning and end of summer, indicating a larger resistance to water flow from soil to needles. As the soil water potentials (measured as pre-dawn values) were, at the same time, the highest for the year, it is suggested that these changes in resistance from period to period mainly take place in the trees. Plots of φ against D during clear days, showed marked hysteresis as the result of the simultaneous influence on φ of several environmental factors. Close linear relations resulted when φ was plotted against potential evaporation rate (calculated from the Pennman-Monteith formula). The slopes of these regression lines, essentially the flow resistance, showed marked seasonal variations, with the largest resistance found at the beginning and end of summer. In most periods the water relations of the trees from different provenances were strikingly similar. A continuous change in the water relations of the remote provenances towards the situation for the “home-provenance” is indicated by the experimental results. It is concluded that trees from different latitudes after ten years of growth have about the same chance as the home provenance to survive periods during which their water balance might become critical.     

The Water Relations of Pinus sylvestris

Comparative field studies of transpiration rate and drying-transpiration in Scots pine were carried out in the autumns of 1964 and 1965 and in the early summer of 1966. The experimentl material was nineteen to twinty year old grafts, of the same clone but growing on different types of ground, or of different clones but growing in close proximity and under the same environmental conditions. Transpiration rates were measured on detached shoots. The results indicated that the type of ground did not very much modify the responses of the shoots to illumination-darkness treatment. Drying-transpiration is here defined as the transpiration occurring when detached shoots are prevented from water uptake. Measurements were made of the rate of loss of weight and the amount of water given off from illuminated shoots. Defferences were found both in the rate of weight loss, and in the amount of water given off, between pine trees of the same clone but growing on different types of ground, and between pine trees of different clones but growing on the same type of ground.     

An Examination of the Quantity of Water Stored in Mature Pinus sylvestris L. Trees

Water stored within the tree and released to the transpirationstream was considered as a possible explanation for a discrepancybetween two independent estimates of evaporation from a Pinussylvestris L. plantation in Thetford Chase, East Anglia. A techniqueis described by which an estimate is made of the quantity ofstored water. Trees were allowed to transpire only stored waterand estimates made of the quantity available. The results showed,however, that the amount of water available from store is insignificantand could not account for the discrepancy between evaporationestimates.     

The Water Relations of Pinus sylvestris II. Comparative Field Studies of Water Potential and Relative Water Content

Comparative field studies of water potential and relative water content in needles of Scots pine, Pinus sylvestris L., were carried out in September-October 1965, in June 1966 and in July-August 1968. The sample trees were grafts, planted in 1946 and belonging to two clones, growing in close proximity and under the same environmental conditions. The main subject of the investigation was to determine whether differences in water potential and/or relative water content existed between these two clones, and if these differences could be correlated to the growth differences and thus aid in the development of selection criteria. The results obtained demonstrate such differences in water potential but not in relative water content. The differences were not consistent through the experimental periods. The clone which had the highest water potentials in June 1966, had the lowest in September-October 1965 and in July-August 1968. The results revealed that the clone which showed the fastest total growth, normally had the lowest water potentials when irradiated. In 1968 the current and the previous season's needles were separately investigated. The water potential and relative water content were always higher in the current season's needles. Highly significant negative correlations between water potential or relative water content and irradiance, temperature, and vapour pressure deficit were found.     

The refilling of embolized xylem in Pinus sylvestris L.

Abstract. The hypothesis that ray parenchyma cells are actively involved in the refilling of embolized xylem of Pinus sylvestris L. was tested by killing the ray parenchyma and comparing rehydration of killed stems with that of control material. Killing of ray parenchyma was achieved using hot water or sodium azide. In most experiments, the available water for refilling was at negative water potential. Experiments were done on three kinds of plant material: small branch segments, potted seedlings and small potted trees. In all experiments, there was no indication that the azide-killed xylem was slower to refill than the control material and it was concluded that the parenchyma has no role in the refilling process, which therefore must be purely physical or physicochemical. Stems treated with hot water did not refill; we suggest that this may be caused by high temperatures decreasing the water permeability of the tracheid wall. The refilling of small branch segments may be explained by surface tension forces (capillary action), which inside the tracheid lumen may lower the water potential down to -9.7kPa; this may be enough to draw in water from the available water that in experiment one was at -2kPa. In the case of seedlings or saplings, capillary action cannot explain refilling, because the xylem water potentials were always lower than those estimated from tracheid radii. Condensation of water during diurnal cycles of warming and cooling is also unlikely to contribute to refilling significantly. To account for refilling in these cases, it is supposed that the tracheid wall may be chemically active and able to lower the water potential below the value expected by capillarity.     

Studies in the Growth of Young of Pinus sylvestris L.: I. The Annual Cycle of Assimilation and Growth

The annual cycle of growth in plants of P. sylvestris L. varyingin age from 2 to 5 years was studied mainly by following theirweight changes through periodic sampling. Immediately followingbud-break there was a period of about 1 month in which, althoughmeristematic and extension growth were rapid in both shoot androot, there was no gain in weight by the plant. There was evidencethat the needles remaining from previous years contained a considerableamount of storage material which was utilized at this time.During May and June the main increase in weight was in the newshoots, but in August and September assimilates were more evenlydivided between the new shoots on the one hand, and the oldstem and the root on the other. The average relative growth-ratesfor the months May to September were between 1·0 and0·4 per cent, per day in plants growing in favourableconditions, the lower rates being found in older plants. Duringthe months October to March slow increase in weight occurredin needles, stem, and root, and the R.G.R.s in two experimentswere 0·21 and 0·15 per cent, per day. The netassimilation rate fell with increasing age and in the summerof the fifth year was 0·06g./g./week or 0·10g./dm.²/week.This low value of N.A.R. is discussed in relation to the knownhigh rate of production of P. sylvestris stands and their evergreenhabit.     

The Limits to Xylem Embolism Recovery in Pinus sylvestris L.

In this study we test the hypothesis that, when water supplyis under tension, reversal of cavitation can occur as long aswater continuity is maintained in the vicinity of tracheids.The experiments were conducted on young branches, 7–8mm diameter, of Pinus sylvestris L., freshly collected and allowedto lose water on the bench after being debarked. During dehydration,the volumetric fractions of water (V_w) and gas (V_s) changedsteadily as relative water content () declined. Meanwhile, ultrasonicemissions (UAE) started after a threshold = 90% was reachedand were maximal at = 75%. Before and after dehydration, branchsegments were connected to water-filled tubing and placed from0.2 to 3.6 m above a water source and water inflow and outflowwere recorded. These distances provided a source of water ata potential of –2.0 to –36kPa. We considered thatthe segment water potential would be a function of the surfacetension across the water meniscii at the ends of the embolizedtracheids. Thus, water potentials calculated from tracheid dimensionswould be as low as –43 kPa. Water inflow to segments declinedwhen the distance from the source was increased or the segmentswere very dehydrated. Increasing the distance above the watersource would be expected to increase the water potential differencebut to reduce water uptake. The most dehydrated segments absorbedwater faster at the beginning of the refilling period (2h),but at the end of 16h, was lower and V_g larger than in lessembolized tissue. Recovery of water flow followed a similartrend, and was lowest when embolisms increased. For a narrowrange of , hydraulic conductance was reduced sharply, indicatingthat wide tracheids were still gas-filled. Thus, the numberof tracheids remaining embolized increased when the source waterpotential was low and there was severe embolism. We concludethat embolism can be reversed in P. sylvestris at a rate dependingon the water potential of the source, severity of embolism andhydraulic conductivity. Key words: Pinus sylvestris L., cavitation induction-recovery, embolized tracheids, water content and embolism, matrix potential, capillary, hydraulic conductance     

Plastids and glycolipids in the stemwood of Pinus sylvestris L.

Summary The ultrastructure of plastids in xylem ray parenchyma cells of Pinus sylvestris L. was studied and compared with the glycolipid composition of the stemwood. Seasonal changes of the ultrastructure were studied by taking samples regularly throughout the year. The plastids resemble amyloplasts. They usually have one large starch grain, and considerable variation in structure and starch content was observed, especially in the innermost sapwood and in the sapwood-heartwood transition zone. Electron-dense deposits were observed attached to the plastid membranes and envelopes, especially in the transition zone, from April to November. The plastids were aggregated near the nucleus and the starch disappeared during the winter (January–March). The glycolipids, monogalactosyldiacylglycerol (MGDG) and di-galactosyldiacylglycerol (DGDG), were present only in the sapwood, in trace amounts. The glycolipid content was slightly greater in the outer sapwood than in the sapwood-heartwood transition zone. DGDG was the dominant lipid of the two.     

Glucomannan-synthase activity in differentiating cells of Pinus sylvestris L.

Particulate membrane preparations have been isolated from cambial cells, and from differentiating and differentiated xylem cells of the main stem of pine trees. These preparations synthesise a 14 glucomannan from guanosine 5-diphosphate-mannose. The polysaccharide and the synthase have been characterized and the K_m and V_max for the synthase determined as 85 M and 52.9 M·min^-1, respectively. The enzymic activity was inhibited by the addition of guanosine 5-diphosphate-D-glucose so that the presence of an epimerase on the particulate fraction in conjunction with the synthase probably allowed the heteropolymer to be formed with the optimal ratio of the concentrations of the nucleoside-diphosphate sugar donors. No evidence for a polyprenyl-phosphate derivative as an intermediate during the polymer synthesis was obtained. Part of the control mechanism for the deposition of the large amounts of the glucomannan during the secondary thickening of the tracheids of the vascular system is by an increase in the amount of synthase activity at the endomembrane system of the cells. This probably occurs by an increase in the amount of enzyme which is modulated by gene regulation during differentiation.Abbreviations GDP guanosine 5-diphosphate - GLC gasliquid chromatography     

Isolation and Study of Proanthocyanidins from Bark of Pine Pinus sylvestris L.

Russian Journal of Bioorganic Chemistry - The isolation of proanthocyanidins from the bark of Scotch pine Pinus sylvestris L. by water and water–alcohol solutions containing 5, 10, 15, 20,...     

Aging in Pinus sylvestris L. seeds: changes in viability and lipids

Aging of Scots pine seeds (Pinus sylvestris L.) leads to changes in seed quality, such as loss of germinability, delayed growth and abnormality in developing seedlings. The knowledge of biochemical changes responsible for these aging processes is plentiful in some seeds, which are of world-wide interest, but for pine seeds these studies are rare. The aim of the present study, was to analyse pine seeds of varying ages in order to identify biochemical changes occurring in aged pine seeds, and to see if a correlation existed between these results and traditionally used seed-quality parameters, such as germinability and electrolyte leakage.     

Inheritance of autumn frost hardiness in Pinus sylvestris L. seedlings

Summary Inheritance of frost hardiness was analysed making use of a 12×12 incomplete factorial mating design. Owing to space limitations only 59 families could be tested in four experiments. To link the four experiments, some families were common to two or more experiments. The seedlings were grown in climate chambers under conditions inducing autumn hardening. The plants were exposed to a freezing temperature of –10 °C for three hours at night lengths of 11–13 h. A statistical model was developed for analyses of variance of our data. The genetic variation and the variation due to the cultivation regimes during autumn hardening were of the same magnitude. The additive effects were the most important ones for induction of frost damage. No interaction following long-distance crossing was noted. Mixed model equations were used for ranking of the parents. The results obtained support a polygenic inheritance of frost hardiness. The large within-population variation offers good opportunities for hardiness breeding.     

Some Aspects of Energy Flow in Plantations of Pinus sylvestris L.

Calorific values are given for the different types of plantmaterial in an age series of plantations of Pinus sylvestrisand the amounts of energy in the organic matter present perhectare of woodland are calculated. Following afforestationwith Scots pine a progressive accumulation of energy occursup to 35 years of age when the organic matter present per hectarecontains about 10, 000x10⁸ calories. Values are given for theenergy content of the primary production by the trees and groundvegetation, of energy accumulation in the tree stock, understoryvegetation, and litter, of energy removed in the harvested treesand of energy released by decomposition. The photosyntheticefficiency of the forest community is calculated and shown tobe comparable to that of high producing agricultural crops sothat it is suggested that the forest community makes very fulluse of site conditions.     

The Potassium Relations of Lemna minor L.: I. POTASSIUM UPTAKE AND PLANT GROWTH

A simple expression has been derived to predict the rate ofnet K uptake into exponentially growing plants of Lemna minor.Net uptake predictions are in good quantitative agreement withmeasurements of ‘steady-state’ K influx, indicatingthat, in the ‘steady state’, K movements in theplant are essentially undirectional and that efflux is small.This close matching of inward K movement to the demands of theexpanding tissue is temporarily disturbed if plants are transferredto media of different K status. Uptake rates in the ‘step-up’are initially enhanced and then fall gradually towards a new‘steady-state’ rate. In contrast, the ‘step-down’causes an initial depression of uptake and then rates increasegradually towards the new ‘steady-state’ rate. Itis argued that these changes in uptake rates are associatedwith alterations in the cytoplasmic K content.     

Relations between understorey vegetation,site productivity,and environmental factors in Pinus sylvestris L. stands in southern Finland

Relations between understorey vegetation, site productivity, and environmental factors in mature stands of Pinus sylvestris L. in southern Finland were studied using data from 234 sample plots. The (weighted) Pearson product-moment correlation between site index and the first ordination axis of detrended correspondence analysis (DCA) was 0.83. The correlation was clearly better where site index was above 21 m (r=0.83) than where it was less (r=0.33). Partial canonical correspondence analysis (CCA) indicated that the residual compositional variation, not related to site fertility as expressed by site index, can be partly ascribed to high moisture regime with poor drainage (paludification), soil deposit type, soil stoniness, and macroclimate, and in part to unexplained sources. The unique influence of canopy cover on the vegetation composition was non-significant (p<0.05) and that of stand age too small to be detected in the vegetation data. The results support Cajander's forest site type theory according to which there exists a dominant relationship between understorey vegetation and site productivity in boreal forest ecosystems. Cladonia sectio Cladonia lichens, exluding Cladonia uncialis, were treated collectively, and abbreviated as Cladonia spp. The most frequent of these species were C. gracilis, C. cornuta, C. fimbriata, C. deformis, C. cenotea, C. botrytes, C. crispata, C. pyxidata, C. cornuta, and C. furcata.     

Changes of morphogenic competence in mature Pinus sylvestris L. buds in vitro

The effects of season and cold storage on morphogenic competence in mature Pinus sylvestris buds were investigated. Peroxidase and polyphenol oxidase activity were measured as markers of oxidative metabolism. No growth in vitro was observed on explants detached from the end of January until the beginning of March. Brachioblasts, each with a couple of needles, formed on 11% of the buds without macrostrobili that were detached in early April and introduced immediately into culture. Of the explants detached in late July, 15% formed shoots with brachioblasts and needles. The lowest activity of peroxidase and polyphenol oxidase in pine buds was observed from the end of April until the beginning of June when morphogenic competence of tissues started to increase. Development of bud explants detached in January was achieved by cold storage for 5 months. Low polyphenol oxidase and peroxidase activity coincided with increased morphogenic potential. Results suggest that reduced or stable activity of peroxidase and polyphenol oxidase is associated with an increased ability of tissues to start growth in vitro.     

Protein Biosynthesis in the Embryo and Endosperm during Embryogenesis in Pinus sylvestris L.

Protein biosynthesis in the embryo and endosperm during embryogenesis in the Scots pine was studied using electrophoretic and immunochemical methods. Proteins of the albumin-globulin fraction were visualized already at the early embryonic stages. The major polypeptide components (48–60, 37–39, and 20–22 kDa) were gradually accumulated in the course of maturation. A high synchrony was noted between the stages of embryogenesis and molecular events related to protein biosynthesis and accumulation in the developing seed.