Interactions between hosts and non-hosts of Pinus spp. and Matsucoccus josephi: anatomical responses of stem to infestation

Artificial infestation of seven pine species revealed that Matsucoccus josephi (Homoptera: Margarodidae) completes its development on Pinus brutia , P. eldarica and P. halepersis , whereas only a small number of the scale larvae infesting P. cunariensis and P. pined reached the second instar and none developed to the adult stage. M. josephi crawlers died while trying to feed on P. radiata and P. pinaster. Histological examination of the infested plant sections indicated that necrosis in shoot and stem barks of P. eldarica and P. halepensis occurs just before or after the scale completes its development. Injury reached the cambium, and traumatic resin ducts; parenchyma cells instead of tracheids and curved tracheids were formed. In P. brutia wound periderm was observed in the stem section but not in the shoot cortex following scale development. Wound periderm was also formed in the stem cortex of P. canariensis and P. pinena whereas no pathological changes were detected in the infested cortex of P. pinaster and P. radiata.
Mechanical lesions caused by needle punctures resulted in the production of parenchyma cells instead of tracheids in all four pine species investigated. The response of the pine cortex was non-specific; however several similarities in the response to scale infestation, such as the formation of resin ducts, were observed. We hypothesize that the response of the pine tissue to the scale saliva is a hypersensitive reaction. It is suggested that the development of Matsucoccus species on particular pine species is related to the scale's inability to trigger the defence system of the host while the larvae are feeding.     

The effects of ultraviolet-B radiation on loblolly pine. I. Growth, photosynthesis and pigment production in greenhouse-grown seedlings

One-year old loblolly pine ( Pinus taeda L.) seedlings were grown in an unshaded greenhouse for 7 months under 4 levels of ultraviolet-B (UV-B) radiation simulating stratospheric ozone reductions of 16, 25 and 40% and included a control with no UV-B radiation. Periodic measurements were made of growth and gas exchange characteristics and needle chlorophyll and UV-B-absorbing-compound concentrations. The effectiveness of UV-B radiation on seedling growth and physiology varied with the UV-B irradiance level. Seedlings receiving the lowest supplemental UV-B irradiance showed reductions in growth and photosynthetic capacity after only 1 month of irradiation. These reductions persisted and resulted in lower biomass production, while no increases in UV-B-absorbing compounds in needles were observed. Seedlings receiving UV-B radiation which simulated a 25% stratospheric ozone reduction showed an increase in UV-B-absorbing-compound concentrations after 6 months, which paralleled a recovery in photosynthesis and growth after an initial decrease in these characteristics. The seedlings grown at the highest UV-B irradiance (40% stratospheric ozone reduction) showed a more rapid increase in the concentration of UV-B-absorbing compounds and no effects of UV-B radiation on growth or photosynthetic capacity until after 4 months at this irradiance. Changes in photosynthetic capacity were probably the result of direct effects on light-dependent processes, since no effects were observed on either needle chlorophyll concentrations or stomatal conductance. Further studies are necessary to determine whether these responses persist and accumulate over subsequent years.     

Different effects of supplied ammonium on glutamine synthetase activity in mustard (Sinapis alba) and pine (Pinus sylvestris) seedlings

The activity of glutamine synthetase (GS) in mustard ( Sinapis alba L.) and Scots pine ( Pinus sylvestris L.) seedlings was used as an index to evaluate the capacity to cope with excessive ammonium supply. In these 2 species GS activity was differently affected by the application of nitrogen compounds (NH₄⁺ or NO₃⁻). Mustard seedlings older than 5 days showed a considerable increase in GS activity after NH₄⁺ or NO₃⁻ application. This response was independent of the energy flux, but GS activity in general was positively affected by light. Endogenous NH₄⁺ did not accumulate greatly after nitrogen supply. In contrast, seedlings of Scots pine accumulated NH₄⁺ in cotyledons and roots and showed no stimulation of GS activity after the application of ammonium. In addition, root growth was drastically reduced. Thus, the pine seedlings seem to have insufficient capacity to assimilate exogenously supplied ammonium. NO₃⁻, however, did not lead to any harmful effects.     

Putrescine metabolism in excised cotyledons of Pinus radiata cultured in vitro

The metabolism of ¹⁴C-putrescine and the changes in the endogenous concentrations of putrescine, spermidine and spermine were studied when cotyledons of Pinus radiata D. Don were cultured under shoot-forming (SF, + N⁶-benzyladenine) and non-shoot-forming (NSF, - N⁶-benzyladenine) conditions. Differences in the total uptake of ¹⁴C-putrescine during a 2 h pulse feeding were not significant between the SF and NSF cotyledons except on day 3. The maximum uptake of label was on day 3 in the SF cotyledons, which released the highest amount of ¹⁴CO₂ as well. ¹⁴C from the labeled putrescine was incorporated mainly into γ-aminobutyric acid, aspartate and glutamate. High performance liquid chromatography of the endogenous polyamines indicated that spermidine was the most predominant polyamine in the cultured cotyledons of radiata pine. Spermine increased by about 60% in the SF and 25% in the NSF cotyledons between days 0 and 3 of culture.     

The influence of crabs on litter processing in high intertidal mangrove forests in tropical Australia

Summary Measurements of litter fall and litter removal by crabs, in conjunction with estimates of litter decay by microbes and tidal export of litter from three high-intertidal mangrove forests were made during a year-long study in tropical northeastern Australia. In forests dominated by Ceriops tagal and Bruguiera exaristata, litter standing stocks remained low on the forest floor (mean 6 g·m^-2), although litter fall was high; 822 and 1022 g·m^-2·y^-1, respectively. Sesarmid crabs removed 580 (Ceriops) and 803 (Bruguiera) g·m^-2·y^-1, or 71 and 79%, of the total annual litter fall from the forest floor. Relative to the rate of litter removal by crabs, microbial turnover of whole, unshredded litter was insignificant, accounting for <1% of annual litter fall. Export of litter by tides was estimated to remove 194 (Ceriops) and 252 (Bruguiera) g·m^-2·y^-1 or 24 and 25% of annual litter fall. In a forest dominated by Avicenniamarina, in which an ocypodid crab was more abundant than sesarmids, litter standing stocks were higher (mean 84 g·m^-2) and crabs removed less litter; 173 g·m^-2·y^-1 or 33% of the annual litter fall of 519 g·m^-2·y^-1. Microbial turnover of intact litter was more important in the Avicennia forest (168 g·m^-2·y^-1 or 32% of annual litter fall), and tides exported 107 g·m^-2·y^-1 or 21% of litter production. In areas where sesarmid crabs were absent or rare in Ceriops forests, there were significantly higher standing stocks of litter and slower rates of leaf removal. Taking into account the probable assimilation efficiencies of sesarmid crabs feeding on mangrove leaves, we estimate that in Ceriops and Bruguiera forests leaf processing by crabs turns litter over at >75 times the rate of microbial decay alone, thus facilitating the high sediment bacterial productivity in these forests. The importance of litter processing by crabs increases with height in the intertidal in tropical Australia, in contrast to New World mangrove forests, where the reverse is true.Contribution No. 445 from the Australian Institute of Marine Science     

Seasonal changes in the pigments, carbohydrates and growth of red spruce as affected by ozone

Two-year-old red spruce seedlings were exposed to various levels ot ozone, from 0.4 to 3 times ambient levels, in open-top chambers in Ithaca, NY, USA. Exposures, which varied with changes in day length, commenced on May 30, 1987 and continued until December 14, 1987. Seedling biomass, carbohydrate contents, pigment contents, and rate of electron transport were assessed twice monthly during the fumigation period. Orthogonal quadratic or cubic polynomials were used to model the response through time each variable measured. A one-way analysis of variance model was fitted to every regression coefficient in each polynomial model to test for ozone effects on seasonal physiological patterns. Ozone did not influence growth, foliar pigment content, foliar starch content, root carbohydrate content, or rate of electron transport. The seasonal change of needle raffinose content differed between exposed to low (0.4 ×, 1×) and high (2×, 3×) ozone levels. There was also a trend towards reduced total soluble sugar content foliage during late autumn in higher ozone treatments.     

Effects of N-immissions on nutrient status and vitality ofPinus sylvestris near a hen-house

Near a hen house (50–600 m), vitality ofPinus sylvestris, N-, P-, K-, Ca-, Mg-contents of the needles, N-, Mg-, K-, Ca- and Al-contents in soil extracts and NH₃/NH ₄ ⁺ -contents of the air were determined. Damage symptoms occurred when N-immissions hit the canopy directly. In contrast no visible decline of the above ground plant could be observed if N was mainly deposited on the soil.     

Mineralization of carbon and nitrogen in soil samples taken from three fertilized pine stands: Long-term effects

Seven years after fertilization the rate of CO₂ production in the soil samples taken from the organic horizons of a poor pine forest site (Calluna vulgaris site type), treated with urea or ammonium nitrate with lime, was lower than that in the unfertilized soil. The same trend was also observed in samples of theEmpetrum-Calluna site type 14 years after fertilization. In the more fertileVaccinium myrtillus site type these rapidly-soluble N fertilizers had a long-term enhancing effect on the production of CO₂. Apatite and biotite eliminated the decreasing effect of urea on the production of CO₂. One reason for this might be the long-term increase in soil pH caused by apatite and biotite, or their constituents (Ca, Mg, K, P). Nitroform (a slow-releasing N fertilizer) had no statistically significant effect on the production of CO₂ in soil samples from any of the forest types. Despite the high N mineralization in the samples from nitroform fertilized soils there was no nitrification, and the high content of total N indicated that after nitroform fertilization the losses of N were low.The correlation between the net mineralization values for C (CO₂ production) and N was poor. However, multiple linear regression analysis, which also took into account the effect of nutrients and pH, indicated that there was a link between the mineralization of C and N.     

An empirical analysis of the factors contributing to 20-year decrease in soil pH in an old-field plantation of loblolly pine

The pH of weak-acid solutions is controlled by acid concentration (HA + A^–), the degree of acid dissociation (A^–/HA), and the strength of the acids present (pK_a). We developed an empirical approach that allows the relative importance of each of these factors to be estimated for soils. This empirical model was applied to soils collected from an old-field plantation of loblolly pine (Pinus taeda L.) at 5 and 25 years of age. During this period, soil pH dropped by 0.3 to 0.8 units, and extractable calcium, magnesium and potassium declined by 20 to 80%. The empirical model indicates that the decline in pH resulted largely from the reduction in base saturation of the exchange complex. However, the average acid strength of the exchange complex decreased during the 20 years, preventing a greater decline of perhaps 0.1 to 0.2 units in the observed pH. The rate of decrease in the acid neutralizing capacity to pH 3.5 was about 1.3 kmol_c/ha annually, while the increase in base neutralizing capacity was about 2.7 and 1.6 kmol_c/ha annually to pH 5.5 and 8.2, respectively. Extractable alkali and alkaline earth cations declined by about 2.2 kmol_c/ha annually, matched by the rate of increase in aluminium. These changes demonstrated the dynamic nature of poorly buffered soils, and indicated that changes in soil acidity may be expected over a period of decades (especially following changes in land-use).     

云南呈贡梁王山现代花粉雨的研究

本文通过对云南呈贡梁王山5块表土分析,初步研究了主要植物花粉的百分含量与其植物覆盖率之间的数量关系,并用校正系数R值表示。按照R值的大小,分为两组:R>1属于超代表性,包括有松、桤木、马桑、蒿和部分蕨类植物;R<1属于低代表性,包括有油杉、栲和石栎、滇青冈、栎、铁仔。在分析松粉分布特征基础上,认为昆明地区西风急流对松粉的传播是主要因素。