Effect of flooding of soil on growth,stem anatomy,and ethylene production of cryptomeria japonica seedlings

Flooding of soil for 55 days altered the rate of growth and stem anatomy of 9‐month‐old Cryptomeria japonica seedlings. Although flooding did not affect height growth it reduced the rate of dry weight increment of seedlings while increasing stem diameter. The reduction in dry weight increment of seedlings resulted largely from decay of roots and, to a lesser extent, from inhibition of growth of roots and needles. The increased diameter growth of flooded seedlings resulted largely from an increase in bark thickness associated with increased phloem production and greater amount of intercellular space. Flooding reduced xylem increment in submerged stems but increased it above the water level because of larger tracheids rather than more tracheids per radial file. Flooding also increased lumen diameters of tracheids, decreased tracheid wall thickness (as a proportion of tracheid diameter), and stimulated formation of axial parenchyma cells in the xylem. Cryptomeria japonica seedlings adapted to flooding by forming adventitious roots, primarily on the original root system and submerged portion of the stem. Such new roots originated in the xylem ray parenchyma. Flooding stimulated ACC synthesis in roots and ethylene production in stems. The role of ethylene in alteration of stem anatomy is discussed.     

Response of ethylene and chlorophyll in two eucalyptus clones during drought

A study was conducted with seven-month-old plantlets, of the clone 2814 of Eucalyptus grandis × E. camaldulensis Dehnh. hybrid and of the clone 2798 of E. grandis × E. robusta Sm., subjected to sublethal water stress. During the imposed drought, leaf water potentials and transpiration rates decreased, while ethylene production and leaf chlorophyll concentration increased to a maximum during the onset of water stress, and then declined. Stomatal closure coincided with or preceded maximum ethylene production. A saturation type relationship between ethylene production and chlorophyll concentration was observed. Genotypic differences in the response to water stress occurred between clones with clone 2814 appearing to be a drought avoider and clone 2798 a drought tolerator.     

Photosynthesis in Norway spruce seedlings infected by the needle rust Chrysomyxa rhododendri

Chrysomyxa rhododendri (DC.) De Bary is a needle rust with a host shift between Rhododendron sp. and Norway spruce (Picea abies (L.) Karst.), penetrating only the new developing flushes of the conifer. Because little is known about its effects on trees, we investigated several parameters related to photosynthesis in artificially infected 3-year-old Norway spruce seedlings. The potential efficiency of photosystem II (PSII; derived from chlorophyll fluorescence measurements) was reduced in infected current-year needles as soon as disease symptoms were visible, about three weeks after inoculation. Two weeks later, photosynthetic O(2) evolution (P(max)) of infected needles was less than 20% of control needles, whereas respiratory O(2) uptake (R(D)) was about three times higher than that of control needles. Nonstructural carbohydrate concentrations were about 60% of control values in all parts of the shoots of infected trees. Photosynthetic inhibition was associated with marked decreases in chlorophyll concentration and chlorophyll a/b ratio but only a small reduction in carotenoid concentration. In infected trees, P(max) of noninfected 1-year-old and 2-year-old needles was 50 and 80% higher than in the corresponding age class of needles of control trees. Estimation of potential daily net dry mass production, based on P(max), R(D), specific leaf area, carbon content and needle biomass, indicated that seedlings infected once were able to produce 60%, and those infected twice only 25%, of the dry mass of controls. We conclude that afforestation and regeneration of Norway spruce is seriously impaired in regions where seedlings are frequently attacked by Chrysomyxa.     

Ethylene evolution,radial growth and carbohydrate concentrations in Abies balsamea shoots ringed with Ethrel

The terminal (1-year-old) shoot of quiescent, 2-year-old Abies balsamea (L.) Mill. seedlings was either left untreated or ringed with 0, 1 or 10 mg Ethrel g(-1) lanolin. After 5 weeks of culture under environmental conditions favorable for growth, the shoots were harvested to measure ethylene evolution and carbohydrate concentrations by gas chromatography, and tracheid number and bark radial width by microscopy. In untreated shoots, the basal rate of ethylene evolution followed the order: cambial region > cortex + periderm = xylem + pith = needles. Wound-induced ethylene production was not detected until at least 4 h after excision, but was evident in all fractions 24 h after excision; the increase in wound-induced ethylene evolution followed the order: cambial region > cortex + periderm > xylem + pith > needles. Compared with untreated controls, the application of plain lanolin, which involved the removal of needles and periderm, increased bark radial width and wound-induced ethylene production by the cambial region and the cortex + periderm, but decreased cambial region concentrations of fructose, glucose and starch at the application point. At the application point, Ethrel concomitantly increased ethylene evolution from the cambial region and the cortex + periderm, tracheid number, bark radial width, and the cambial region concentrations of fructose, glucose, sucrose and starch. No effects of Ethrel treatment were detected above or below the application point, with the exception that the 10 mg g(-1) Ethrel treatment stimulated ethylene evolution and decreased starch concentration of the cambial region. The results indicate that: (1) the cambial region is the major source of endogenous ethylene in the 1-year-old shoot; (2) the magnitude of the difference in ethylene evolution between particular shoot fractions is different before and after the start of wound-induced ethylene production; (3) the Ethrel-induced increase in tracheid number and bark radial width at the application point is positively related to ethylene evolution from the cambial region and the cortex + periderm, respectively; and (4) ethylene derived from Ethrel applied laterally to a woody stem can mobilize carbohydrates to the application point.     

Effects of salicylic acid, 1‐aminocyclopropan‐1‐carboxylic acid and methyl jasmonate on the frequencies of endophytic fungi in Quercus serrata leaves

To examine the effects of salicylic acid (SA), the ethylene precursor 1‐aminocyclopropan‐1‐carboxylic acid (ACC) and methyl jasmonate (MJ), which induce defence responses against pathogen in plants, on foliar endophytic fungi, we performed exogenous treatments of Quercus serrata leaves with these chemicals and subsequently isolated endophytic fungi. SA and ACC significantly reduced the isolation frequency of the most dominant fungus, a Xylaria species as identified by sequence analysis of the internal transcribed spacer (ITS) region of the ribosomal DNA. In contrast, the frequency of the second most frequent fungus increased by SA and ACC. A few other fungi were also affected positively or negatively. Shannon diversity indices decreased by all treatments because of the uneven isolation frequencies of the endophytes. Our results imply that host defence responses induced by the chemical treatments reduced the number of infections of some endophytes while the frequency of some other endophytes increased benefiting from the reduction of competitors.     

RELATIONSHIP BETWEEN SCOTCH PINE NEEDLE RUST AND HOST CHLOROPHYLL CONTENT

PhotoSynthe3isisaprocessofaccumulat-ingorganicmaterialsinthylakoidmembranesofgreenplantchloroplast.Whentheleavesofgreenplantaredestroyedbysomefactor,chlo-rophyllcontentwillchange,whichcanaffeetorganicmaterialsaccumulatonandharmtreegrowth.TherearesomerePortsonrelationshipbetWeentreechlorophyllcontentanddifferentstandsmictUre,differentsiteconditionanddifferentgrowthperiod,buttherePOrtsontreedisease,especiallytheeffectsofneedlesrustonchlorophyllcontCnthavenotbeenseen.lntl1isstUd3,thechlorophyl…     

叶型对马尾松幼苗生长及叶绿素荧光特征的影响

【目的】研究叶型对马尾松幼苗生长及叶绿素荧光特征的影响,以期为马尾松苗木选择及栽培提供参考。【方法】以出圃时呈现为全初生条形叶、全次生针形叶和中间型的马尾松1年生幼苗为试验材料,分析其生长指标、光合色素含量及叶绿素荧光参数,研究初生叶和次生叶叶绿素荧光特征差异及对幼苗生长的影响。【结果】全次生叶幼苗出圃时苗木质量指数(QI)、干物质积累量及造林1年后净生长量均显著高于全初生叶幼苗;次生叶的叶长、体积和表面积等指标均显著大于初生叶;初生叶中叶绿素a、叶绿素b和总叶绿素含量均显著高于次生叶,两者间的类胡萝卜素含量无显著差异。初生叶的F_m、F_v/F_m、F_v/F_o均显著高于次生叶,F_o在2种叶型间无显著差异;初生叶的PSⅡ反应中心参数Y(Ⅱ)和F_v’/F_m’、淬灭参数q_P和NPQ、能量耗散参数Y(NPQ)和Y(NO)及光响应参数ETR_max、α、β和I_k也均高于次生叶,在高光强条件下,初生叶的非光化学淬灭和调节性能量耗散能力增强。由于次生针叶叶长、体积和表面积等形态指标均显著大于初生叶,因而具有次生针叶的幼苗的光合作用面积更大,干物质量积累较多,出圃时的苗木质量以及造林后的生长表现均高于全初生叶的幼苗。【结论】与次生叶相比,初生叶拥有较高的叶绿素含量,较耐光抑制,有较高的光能转化效率,但高光强条件下会通过热耗散的形式来减少多余光能对光合系统的损害;拥有次生叶的幼苗表现出较好的苗木质量及生长特性。     

The effects of long‐term exposure to simulated acid rain on the development of pine wilt disease caused by Bursaphelenchus xylophilus

To elucidate the synergetic effects of acid rain on the development of pine wilt disease, we measured the sap flow rate in the stems and the chlorophyll content in the needles of 10‐year‐old Japanese black pine trees, Pinus thunbergii and 12‐year‐old Japanese red pine trees, Pinus densiflora, after exposure to simulated acid rain (SAR, pH 3) or tap water (TW, pH 6.3) as a control. The heat pulse method was used for the estimation of the sap flow rate. No apparent difference was found in the sap flow rate between the trees exposed to SAR and TW, but the chlorophyll content of needles at the end of the treatment was significantly higher in the trees exposed to SAR than in those exposed to TW. When the pinewood nematode, Bursaphelenchus xylophilus, the causal agent of pine wilt disease, was inoculated onto the Japanese black pines that had been exposed to SAR repeatedly for 1 year, the period to death was shortened. Japanese red pines that had been exposed to SAR for 2 years, however, did not show any development of symptoms after the nematode inoculation, suggesting that acid rain only affects pine wilt disease slightly, if at all.     

Mise en évidence d'une relation entre la teneur en fluor et la chute de production dans les forêts résineuses soumises à une pollution fluorée

The relationship between fluoride content of needles and decrease in yield in conifer forests subject to fluorine pollution . In conifer forests (Picca abies Lk.), subject to fluoride pollution, a logarithmic correlation exists between the F-content of unwashed needles and the decrease in wood production.     

Recovery of photosynthesis in 1-year-old needles of unfertilized and fertilized Norway spruce (Picea abies (L.) Karst.) during spring

Photosynthetic O(2) evolution and chlorophyll a fluorescence were measured in 1-year-old needles of unfertilized and fertilized trees of Norway spruce (Picea abies (L.) Karst.) during recovery of photosynthesis from winter inhibition in northern Sweden. Measurements were made under laboratory conditions at 20 degrees C. In general, the CO(2)-saturated rate of O(2) evolution was higher in needles of fertilized trees than in needles of unfertilized trees over a wide range of incident photon flux densities. Furthermore, the maximum photochemical efficiency of photosystem (PS) II, as indicated by the ratio of variable to maximum fluorescence (F(V)/F(M)) was higher in needles of fertilized trees than in needles of unfertilized trees. The largest differences in F(V)/F(M) between the two treatments occurred before the main recovery of photosynthesis from winter inhibition in late May. The rate of O(2) evolution was higher in needles of north-facing branches than in needles of south-facing branches in the middle of May. Simultaneous measurements of O(2) exchange and chlorophyll fluorescence indicated that differences in the rate of O(2) evolution between the two treatments were paralleled by differences in the rate of PS II electron transport determined by chlorophyll fluorescence. We suggest that, during recovery of photosynthesis from winter inhibition, the balance between carbon assimilation and PS II electron transport was maintained largely by adjustments in the nonphotochemical dissipation of excitation energy within PS II.     

Exploring the relationship between reflectance red edge and chlorophyll concentration in slash pine leaves

Chlorophyll concentration is related positively to the point of maximum slope in the reflectance spectra of leaves and this point is termed the red edge. The reflectance spectra of slash pine (Pinus elliottii Engelm.) needles were measured in the field and the chlorophyll concentrations of the same needles were measured in the laboratory. The measurement errors for red edge and chlorophyll concentration were determined to be 2.2 nm (3% of mean) and 0.35 mg g(-1) (19% of mean), respectively. The red edge-chlorophyll concentration relationship was strong (r(2) = 0.82, n = 152). A red edge-chlorophyll concentration relationship for n = 100 was used with red edge measurements to estimate chlorophyll concentration with an rms error of 0.31 mg g(-1) (17% of mean, n = 52). The entire red edge-chlorophyll concentration relationship for n = 152 was also used with red edge measurements to estimate the chlorophyll concentration of samples from an earlier experiment with an rms error of 0.47 mg g(-1) (30% of mean, n = 38). We conclude that measures of red edge can be used to estimate the chlorophyll concentration of detached needles in the field with an accuracy similar to that obtained by conventional laboratory measurements.     

Cold acclimation and photoinhibition of photosynthesis accompanied by needle color changes inCryptomeria japonica during the winter

This study focused on the physiological changes inCryptomeria japonica accompanied by needle color changes during the winter. The physiological measurements include gas exchange, chlorophyll fluorescence, pigments, active oxygen scavenging enzymes, and several proteins in the photosynthetic apparatus. The light-saturated photosynthesis decreased during the winter. Total chlorophyll content and chlorophylla/b ratio decreased; meanwhile xanthophyll cycle pigments and lutein contents increased significantly. These results indicate that cold acclimation had occurred. Photoinhibition was also observed inC. japonica which can be determined from the decreases in photochemical efficiency of PS II and the partial closure of PS II reaction centers. Small and large subunits of Rubisco and LHC II in the needles ofC. japonica showed only a slight decrease during the winter, indicating that photoinhibition inC. japonica probably reflects a protective process to prevent more severe damage to the photosynthetic apparatus during low-temperature stress. This research was supported by the Bio-oriented Technology Research Advancement Institute (BRAIN), Japan     

Towards resolving Nothophaeocryptopus and Rhizosphaera inhabitants of spruce needles

Our knowledge of the endophytic fungal community associated with needles of Sitka spruce (Picea sitchensis) is rather limited, which contrasts with the importance of this tree species for forestry in the UK. In our study, we focused on the detailed characterization of multiple isolates tentatively placed into the genera Nothophaeocryptopus and Rhizosphaera that were obtained from needles of Sitka spruce and co-occurring Norway spruce (Picea abies) and Douglas fir (Pseudotsuga menziesii) at four sites in Scotland and Wales. After a thorough analysis of their phenotype and analysis of two nuclear regions (ITS rDNA and gene for β-tubulin), we propose two species new to science and one new combination. Nothophaeocryptopus piceae was isolated from healthy green or brown needles from spruces and is currently known only as a sterile culture, but the taxonomic novelty is well supported by host affinity and results of molecular data analysis. Rhizosphaera minteri may also be distinguished based on the combination of host and molecular data, but morphologically, it is similar to R. pini. Finally, Hormonema merioides and R. pseudotsugae are found to be conspecific and a new combination R. merioides is proposed following the phylogenetic placement of this species. Our study highlights the importance of multiple approaches used in the identification of microfungi associated with coniferous needles. It is evident that morphologically identical fungi may represent distinct species differing in their host range and severity on the host. This study also provides a basis for future monitoring of these fungi associated with important coniferous forestry trees in the UK.     

Effect of mineral nutrition content on oxygen exchange and chlorophyll a fluorescence in needles of Norway spruce

Photosynthetic O(2) evolution at high irradiances (approximately 600-1000 micro mol m(-2) s(-1)) and O(2) uptake in darkness were measured in needles of control, irrigated and irrigated-fertilized trees of Norway spruce (Picea abies (L.) Karst.). Measurements were made at 20 degrees C and at high CO(2) concentrations. The results suggest that, at given times of the year, a major part of the variation in gross photosynthesis of current-year and one-year-old needles across treatments is associated with differences in needle N content. Furthermore, the rate of O(2) uptake measured after 5 or 10 min in darkness was positively correlated with both the preceding rate of gross O(2) evolution and the N content in fully expanded current-year needles. Measurements of chlorophyll a fluorescence, taken simultaneously with measurements of O(2) evolution in current-year sun needles, showed that Stern-Volmer quenching of minimum fluorescence and the ratio of variable to maximum fluorescence in the dark- and light-adapted state were strongly correlated with the gross rate of O(2) evolution. This suggests that the increased rate of gross photosynthesis in needles of irrigated-fertilized trees was associated with adjustments in the thermal energy dissipation within photosystem II.     

Leaf gas exchange and growth of flood-tolerant and flood-sensitive tree species under low soil redox conditions

Seedlings of Taxodium distichum L., Quercus lyrata Walt. and Q. falcata var. pagodaefolia Ell. were grown for 22 days in a rhizotron system providing two soil redox potential regimes, +170 mV (low Eh) and +560 mV (high Eh). Leaf chlorophyll concentration and gas exchange, root alcohol dehydrogenase (ADH) activity, root and leaf ethylene production, and growth and biomass partitioning were measured. In response to the low Eh soil treatment, stomatal conductance was reduced in Q. falcata and Q. lyrata but not in T. distichum, whereas net photosynthesis was reduced significantly in all species; however, net photosynthesis in T. distichum began to recover within 2 weeks of treatment initiation. Within each treatment, mean stomatal conductance and net photosynthesis were significantly greater in T. distichum than in the oak species. Leaf chlorophyll concentration was not affected by the soil treatments. All species showed significant reductions in root and leaf dry weights in response to the low Eh soil condition. The low Eh soil treatment resulted in increased root ADH activity and ethylene production in T. distichum, but had no effect on root ADH activity and ethylene production in the oak species.     

Phenotypic Differences Between Natural and Selected Populations of Picea Abies. I. Frost Hardiness

The frost hardiness of non-juvenile Norway spruce [Picea abies (L.) Karst.] populations growing in northern Sweden (63°54' N) was monitored during 1996-1997. The investigated progenies originated from 12 natural populations and six seed orchards located between 58° N and 68° N in Sweden. Frost hardiness of needles was assessed by measuring chlorophyll fluorescence and electrolyte leakage after freezing. The loss of frost hardiness in 1-yr-old needles during spring occurred slightly earlier in populations originating north of 63°30' N than in those originating further south. Dehardening was slightly delayed in selected populations compared with natural populations of similar origin. The level of frost hardiness during autumn was higher in populations originating north of 63°30' N than in those originating south of this latitude, but there were no clear differences in frost hardiness between selected and natural populations of similar origin. The results are discussed in relation to climatic factors and inherent growth rhythms.     

Dothistroma rhabdoclinis sp. nov. associated with Rhabdocline pseudotsugae on Douglas fir

Dothistroma rhabdoclinis, a new coelomycete on needles of Pseudotsuga menziesii is described. The fungus is associated, possibly as a hyperparasite, with Rhabdocline pseudotsugae, the causal agent of Rhabdocline needle‐cast of Douglas fir. The presence of D. rhabdoclinis interferes with and sometimes completely inhibits the production of ascomata of R. pseudotsugae. The cultural and morphological characters of the new fungus are compared with the only other known member of the genus, Dothistroma septospora.     

Cloning and analysis of cross-intron genomic gene encoding ACO in Paeonia suffruticosa Andr.

The last step of ethylene biosynthesis in higher plants is to convert 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene by ACC oxidase (ACO). In our investigation, a cross-introns genomic DNA gene encoding ACC oxidase, PsgACO, was isolated from Paeonia suffruticosa. It revealed that PsgACO (FJ855434) has 1281 bases, containing four exons and three introns, encoding 312 amino acids. The four exons stretched from 1 to 105, 217 to 434, 592 to 925 and 1000 to 1281 bases. A splicing junction sequence of all the exon-introns conformed to the GT-AG rule in the cross-intron genomic DNA sequence of the ACO gene. PsgACO showed high homology to many characterized ACC oxidases both at the nucleic acid and amino acid levels. As well, twelve amino acid residues were conserved among many ACOs from other species. A phylogenetic tree analysis indicated that the amino acid of ACOs is quite conserved among the different eudicots. The phylogenetic tree showed that both the tree peony and herbaceous peony are quite isolated taxa. Bioinformatic analysis showed that the molecular weight of ACO is 35.29 kD, with a theoretical pI of 5.25. It is a non-secrete, stable hydrophilic protein, located in the cytoplasm.     

Co‐occurrence of the ascomycete Lophodermium piceae and the rust fungus Chrysomyxa abietis in Norway spruce needles

The frequency of needles and the proportion of needle segments infected by Lophodermium piceae were compared in symptomless and Chrysomyxa abietis‐infected, 1‐year‐old needles of Picea abies. In late spring, symptomless needles from both rust‐infected and healthy saplings were sampled. In addition, rust‐infected, totally chlorotic needles and needles with chlorosis along about half their length from the diseased trees were examined. In all three stands, the proportion of segments infected by L. piceae was larger in the rust‐infected half of the needle than in the symptomless half; but the difference was statistically significant in only one of the stands. The proportion of L. piceae‐infected segments among the nonrust‐infected needles was the same as that found for the uninfected half of rust‐infected needles (after correction for size differences). No differences in the proportion of L. piceae‐infected segments were found between the totally chlorotic, rust‐infected needles and the green needles of diseased or healthy trees.