Pirjo Kainulainen

Drought stress alters the concentration of wood terpenoids in scots pine and Norway spruce seedlings

Drought is known to have an impact on the resistance of conifers to various pests, for example, by affecting resin flow in trees. Little is known, however, about the quantitative and qualitative changes in resin when trees are growing in low moisture conditions. We exposed Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) seedlings to medium and severe drought stress for two growing seasons and analyzed the monoterpenes and resin acids in the main stem wood after two years of treatment. In addition to secondary chemistry, we measured the level of nutrients in the needles and the growth response of seedlings. After the first year of treatment, drought stress did not affect the growth of seedlings, but in the second year, shoot growth was retarded, especially in Scots pine. In both conifer species, severe drought increased the concentrations of several individual monoterpenes and resin acids. Total monoterpenes and resin acids were 39 and 32% higher in severe drought-treated Scots pine seedlings than in the controls, and 35 and 45% higher in Norway spruce seedlings. In Scots pine needles, the concentrations of nitrogen and phosphorus increased, while magnesium and calcium decreased compared to controls. In Norway spruce needles, nutrient concentrations were not affected. The results suggest that drought stress substantially affects both the growth of conifers and the chemical quality of the wood. We discuss the potential trade-off in growth and defense of small conifer seedlings.

Application of methyl jasmonate reduces growth but increases chemical defence and resistance against Hylobius abietis in Scots pine seedlings

Scots pine (Pinus sylvestris L., Pinaceae) produces a terpenoid resin which consists of monoterpenes and resin acids that offer protection against herbivores and pathogen attacks. Methyl jasmonate (MJ) is a potential plant elicitor which induces a wide range of chemical and anatomical defence reactions in conifers and might be used to increase resistance against biotic damage. Different amounts of MJ (control, 10 mm, and 100 mm) were applied to Scots pine to examine the vigour, physiology, herbivory performance, and induction of secondary compound production in needles, bark, and xylem of 2‐year‐old Scots pine seedlings. Growth decreased significantly in both MJ treated plants, and photosynthesis decreased in the 100 mm MJ treated plants, when compared to 10 mm MJ or control plants. The large pine weevil (Hylobius abietis L.) (Coleoptera: Curculionidae) gnawed a significantly smaller area of stem bark in the 100 mm treated plants than in the control or 10 mm treated plants. The 100 mm MJ treatment increased the resin acid concentration in the needles and xylem but not in the bark. Furthermore, both MJ treatments increased the number of resin ducts in newly developing xylem. The changes in plant growth and chemical parameters after the MJ treatments indicate shifts in carbon allocation, but MJ also affects plant physiology and xylem development. Terpenoid resin production was tissue‐specific, but generally increased after MJ treatments, which means that this compound may offer potential protection of conifers against herbivores.

Effects of nitrogen fertilization on secondary chemistry and ectomycorrhizal state of scots pine seedlings and on growth of grey pine aphid

Effects of nitrogen availability on secondary compounds, mycorrhizal infection, and aphid growth of 1-year-old Scots pine (Pinus sylvestris L.) seedlings were studied during one growing season. Seedlings were fertilized with nutrient solutions containing low, optimum, and two elevated (2 × and 4 × optimum) levels of NH4NO3. At the end of growing season foliar nitrogen concentration, needle biomass, needle length, water contents of needles, root collar diameter, and number of buds increased with enhanced nitrogen availability. Addition of nitrogen did not have effect on concentrations of monoterpenes in growing needles, but in mature needles significantly decreased concentrations of some individual and total monoterpenes were detected. In growing needles the concentrations of some individual resin acids decreased, and in mature needles concentrations of some individual and total resin acids increased with increased nitrogen fertilization. Higher numbers of resin ducts were found in mature needles with nitrogen fertilization. Nitrogen fertilization decreased total phenolic concentrations in growing and mature needles of the current year, but in needles of the previous year no significant differences occurred. Mycorrhizal infection was highest at medium (optimum and 2 × optimum) nitrogen fertilization levels. The relative growth rate (RGR) of grey pine aphid [Schizolachnus pineti (F.)] responded positively to the increase in foliar nitrogen content. However, the increase in aphid performance between optimum and the highest fertilization level was slight. This may indicate a deterring effect of resin acids on aphids. The results indicate that carbon/nutrient balance hypothesis fails to predict directly the effects of nitrogen availability on concentrations of carbon-based defensive compounds in mature foliage. Altered nitrogen supply affects allocation to secondary metabolites differently, depending on the developmental state of the plant and the biosynthesis pathway, cost of synthesis, and storage of compounds.

Concentrations of secondary compounds in Scots pine needles at different stages of decomposition

Abstract A litterbag experiment was conducted to study chemical changes in decomposition of Scots pine needle litter in central Finland. Concentration of secondary metabolites (terpenes, resin acids and total phenolics) and main nutrients (N, P, K, Ca and Mg) were analysed four times over a 19-month period. After 19 months decomposition, the mass loss by pine needle litter was about 22%. Initial concentrations of monoterpenes and total phenolics were 36 and 27% lower in needle litter than in green needles, respectively, while more (44%) resin acids were found in needle litter than in green needles. Concentrations of monoterpenes were 6%, resin acids 35% and total phenolics 17% of the initial concentration after 19 months decomposition. In green needles and senescent brown needles most common monoterpenes were α-pinene and 3-carene. During the decomposition monoterpenes, sabinene, myrcene, limonene+β-phellandrene, terpinolene and bornylacetat, were lost to a greater extent than α-pinene, camphene and tricyclene. At the end of decomposition experiment several oxygen-containing hydrocarbons were detected in terpene samples. The most commonly identified compounds were verbenone and verbenol. Resin acid composition also changed substantially during decomposition, neoabietic acid decomposed faster than other resin acids. Dehydroabietic acid was the main resin acid in needle litter after 19 months decomposition. The concentrations of N, P and Ca significantly increased during decomposition, while concentrations of Mg and K decreased. The results suggest that degradation of secondary organic compounds in needle litter is a slow process and these compounds might have effects on decomposer organisms for several years after needle abscision.

Comparing the Variation of Needle and Wood Terpenoids in Scots Pine Provenances

We determined variation in both the concentration and composition of terpenoids in needles and wood within nine Scots pine (Pinus sylvestris) provenances. Seedlings of different provenances representing a 1200-km N–S transect from Estonia to northern Finland were cultivated in Suonenjoki nursery field, central Finland, for seven years. Growth of seedlings and the number of vertical resin ducts in wood were also determined. α-Pinene and 3-carene were the major monoterpenes both in the needles and wood. The total monoterpene concentration was about five times higher in the needles than in the wood. A strong positive correlation was found between proportional quantities of several terpenes of the needles and wood, particularly for 3-carene, sabinene, and terpinolene. The needles contained both labdane-type and tricyclic resin acids, whereas the wood contained only tricyclic ones. The wood had a four times higher tricyclic resin acid concentration than the needles. The highest total monoterpene concentration in the needles and in the wood occurred in the most northern Muonio provenance and in the most southern Saaremaa provenance plants, respectively. The amount of high 3-carene genotype trees decreased among the northern provenances. The wood of the most northern Muonio provenance showed the lowest total resin acid concentration, but provenance did not affect total tricyclic resin acids in the needles. Korpilahti provenance trees from central Finland had the best growth in height. In addition, Korpilahti and Ruokolahti provenance trees showed largest radial growth of stem and smallest number of vertical resin ducts. The results suggest that especially the proportional quantity of 3-carene in the needles could be used in estimating the amount of this compound in the wood and vice versa.

The influence of elevated CO2 and O3 concentrations on Scots pine needles: changes in starch and secondary metabolites over three exposure years

Abstract Scots pine (Pinus sylvestris L.) trees, aged about 20 years old, growing on a natural pine heath were exposed to two concentrations of CO2 (ambient CO2 and double-ambient CO2) and two O3 regimes (ambient O3 and double-ambient O3) and their combination in open-top chambers during growing seasons 1994, 1995 and 1996. Concentrations of foliar starch and secondary compounds are reported in this paper. Starch concentrations remained unaffected by elevated CO2 and/or O3 concentrations during the first 2 study years. But in the autumn of the last study year, a significantly higher concentration of starch was found in current-year needles of trees exposed to elevated CO2 compared with ambient air. There were large differences in concentrations of starch and secondary compounds between individual trees. Elevated concentrations of CO2 and/or O3 did not have any significant effects on the concentrations of foliar total monoterpenes, total resin acids or total phenolics. Significantly higher concentrations of monoterpenes and resin acids and mostly lower concentrations of starch were found in trees growing without chambers than in those growing in open-top chambers, while there were no differences in concentrations of total phenolics between trees growing without or in chambers. The results suggest that elevated concentrations of CO2 might increase foliar starch concentrations in Scots pine, while secondary metabolites remain unaffected. Realistically elevated O3 concentrations do not have clear effects on carbon allocation to starch and secondary compounds even after 3 exposure years.

Anthocyanin and Flavonol Variation in Bog Bilberries (Vaccinium uliginosum L.) in Finland

The flavonoids, anthocyanins and flavonols, in bog bilberries (Vaccinium uliginosum L.) were studied from 15 populations in Finland on a south-north axis of approximately 1000 km. Four anthocyanidin xylosides and 14 flavonol glycosides were tentatively identified by means of HPLC-ESI-MS. Twenty-five major flavonoids were quantified by HPLC-DAD. The averages (+/-standard deviation) in the contents of anthocyanins and flavonols were 1425+/-398 and 1133+/-290 mg/100 g of dry weight, respectively. The most abundant anthocyanidin was malvidin, followed by delphinidin, petunidin, cyanidin, and peonidin. Quercetin was the major flavonol, followed by myricetin, laricitrin, syringetin, and isorhamnetin. Anthocyanins were mostly glucosides, whereas flavonols were mainly conjugated to galactose. The anthocyanin content in the berries from the south was the lowest. The delphinidin content was the highest but the proportion of malvidin the lowest in the north. The total flavonol content and the level of myricetin and quercetin were the highest in the north.

Chemical factors affecting the brown-rot decay resistance of Scots pine heartwood

The cell wall chemistry (amount of hemicellulose, α-cellulose, and total lignin) and the concentration of extractives (total acetone-soluble extractives, resin acids, pinosylvins and the total phenolics quantified as tannin acid equivalents) were studied in brown-rot resistant and susceptible juvenile heartwood of Scots pine (Pinus sylvestris L.). The study material consisted of a total of 18 trees from two 34-year-old progeny trials at Korpilahti and Kerimäki. The trees were selected from among 783 trees whose decay rate had previously been screened in a laboratory test using a brown-rot fungus, Coniophora puteana. Samples from neither location showed any significant difference in the concentration (mg/cm3) of hemicellulose, α-cellulose and total lignin between the decay resistant and susceptible trees. At both locations only the concentration of total phenolics was higher in the decay-resistant heartwood than in the decay-susceptible heartwood. At Korpilahti, the amount of acetone-soluble extractives and the concentration of pinosylvin and its derivatives were higher in the resistant than in the susceptible trees.

Potential for the Use of Exogenous Chemical Elicitors in Disease and Insect Pest Management of Conifer Seedling Production

Elicitors are compounds, which activate chemical defences in plants. Various biosynthetic pathways are acti- vated in treated plants depending on the compound used. The most intensively studied elicitor for manipulating defence pathways in plants is methyl jasmonate, which modifies e.g. the production of terpenoids, the main constituents of conifer oleoresin. Other commonly tested chemical elicitors are salicylic acid, methyl salicylate and benzothiadiazole, which af- fect production of phenolic compounds in plants. Both jasmonate-based and salicylate-based elicitors have been shown to have suppressive effects on fungal diseases and insect pests of plants. So far, knowledge regarding the efficiency of elici- tor treatments for enhancing pest and fungal disease resistance of conifer seedlings is very limited. We review current knowledge of the effect of these elicitor compounds on pest and disease resistance in plants, and we analyze the potential pros and cons of using elicitors for future pest management strategies in forest nurseries.

Conifer aphids in an air-polluted environment. II. Host plant quality

Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) seedlings were transported to five forest sites at increasing distances from a pulp mill emitting mainly SO(2). Levels of compounds which may have nutritional or defensive value for aphids on pine and spruce seedlings were studied. Glucose and fructose concentrations were significantly increased in pine and spruce needles near the pulp mill. There were no changes in sucrose and starch concentrations. In pine shoots, total free amino acid concentration and the concentrations of ornithine, lysine, histidine and arginine were significantly negatively correlated with the distance from the pulp mill, while in spruce only the individual amino acids glycine, ornithine, lysine and histidine showed a significant negative correlation with distance. There were no changes in total phenolic, catechin, total monoterpene and total resin acid concentrations. However, in pine seedlings monoterpenes beta-pinene and sabinene and in spruce seedlings resin acid palustric acid were significantly correlated with the distance from the pulp mill. The results indicate that SO(2) disturbs carbohydrate metabolism in spruce and pine seedlings. The elevated concentrations of arginine may be the result of the combinations of SO(2), NO(3) and NH(3) emissions of the pulp mill. The emissions did not have any impact on total amounts of defensive substances in trees. Thus, the possible susceptibility of conifers to herbivores appears to be due to changes in nutritive value rather than to reduced chemical resistance.