Inhibitory activity of homoisoflavonoids from Caesalpinia sappan against Beauveria bassiana

Four homoisoflavonoids, 4-O-methylsappanol (1), protosappanin A (2), brazilin (3) and caeasalpin J (4), isolated from Caesalpinia sappan, were tested for inhibitory activity against Beauveria bassiana. Compound 1 showed activity against this fungus.     

Response of Douglas-fir seedlings to a brief pulse of 15N-labeled nutrients

The temporal distribution of soil nutrients is heterogeneous, and thus the uptake, storage and later remobilization of brief nutrient pulses may be critical for growth in nutrient-limited habitats. We investigated the response of 2-year-old Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings receiving a low nutrient supply to a 15-day nutrient pulse (containing 250 ppm nitrogen (N) as 10 atom % 15NH4 15NO3). The nutrient pulse was imposed in late July, toward the end of the seedlings' third growing season, and subsequent changes in dry mass and N content over the following 3 months were determined from destructive harvests. We tested three hypotheses: (1) N from the nutrient pulse is rapidly assimilated and accumulated primarily in needles and roots; (2) this accumulated N is later remobilized to support new growth; and (3) the nutrient pulse leads to a larger second flush of shoot growth. Seedlings increased their N content by 175 mg (67%) in response to the nutrient pulse. Nitrogen was taken up preferentially into younger tissues, especially the secondary flush and current-year roots. Immediately after the nutrient pulse, tissue N concentrations were high and supported subsequent increases in dry mass. Over 3 months, seedlings receiving the nutrient pulse added twice as much dry mass as control seedlings, and even after 3 months of growth, N concentrations remained greater than in controls. Current-year and older needles were the only components whose dry mass did not increase over this period. The nutrient pulse increased the size of the second flush, but it was still a minor component of increments in dry mass (approximately 10% of the total dry mass increment) and N content (23%). The relatively modest increases in N content during autumn could be accounted for by soil uptake and there was no evidence that N was remobilized to support growth of new tissues. Short-term (15 days) elevated N uptake led to sustained growth in the long term (> 3 months), and thus growth rate was to a large extent decoupled from current nutrient supply.     

Antinociceptive activity of Wrightia tinctoria bark

The ethyl acetate, acetone and methanol extracts of Wrightia tinctoria bark showed antinociceptive activity on acetic acid-induced writhing test in mice, their effects being comparable to that of acetylsalicylic acid.     

Biological activity of Glechoma hederacea

The n-hexane, dichloromethane and methanol extracts of the aerial parts of Glechoma hederacea have been screened for antibacterial and free radical scavenging activity. General toxicity (brine shrimp lethality assay) of these extracts has also been assessed.     

Elevated CO₂ enhances leaf senescence during extreme drought in a temperate forest

In 2007, an extreme drought and acute heat wave impacted ecosystems across the southeastern USA, including a 19-year-old Liquidambar styraciflua L. (sweetgum) tree plantation exposed to long-term elevated (E(CO(2))) or ambient (A(CO(2))) CO(2) treatments. Stem sap velocities were analyzed to assess plant response to potential interactions between CO(2) and these weather extremes. Canopy conductance and net carbon assimilation (A(net)) were modeled based on patterns of sap velocity to estimate indirect impacts of observed reductions in transpiration under E(CO(2)) on premature leaf senescence. Elevated CO(2) reduced sap flow by 28% during early summer, and by up to 45% late in the drought during record-setting temperatures. Modeled canopy conductance declined more rapidly in E(CO(2)) plots during this period, thereby directly reducing carbon gain at a greater rate than in A(CO(2)) plots. Indeed, pre-drought canopy A(net) was similar across treatment plots, but declined to ～40% less than A(net) in A(CO(2)) as the drought progressed, likely leading to negative net carbon balance. Consequently, premature leaf senescence and abscission increased rapidly during this period, and was 30% greater for E(CO(2)). While E(CO(2)) can reduce leaf-level water use under droughty conditions, acute drought may induce excessive stomatal closure that could offset benefits of E(CO(2)) to temperate forest species during extreme weather events.     

Methods for inoculum production and inoculation of Cistella japonica,the causal agent of resinous stem canker in Chamaecyparis obtusa

The ascomycete Cistella japonica was cultured on potato dextrose agar medium (PDA) for inoculation into Chamaecyparis obtusa, enabling the development of an inoculation method suitable for use in a breeding programme aimed at selecting for families of Ch. obtusa resistant to resinous stem canker. Using PDA to generate the inoculum resolved the problems encountered with the previously used mixed medium of rice bran and wheat bran, including unfavourable characteristics, uncertain growth of Ci. japonica mycelia, and a complex culturing operation. The inoculation test induced resin exudation similar to that observed in natural infections, and reproduced clonal differences with regard to damage severity.     

The effect of periderm formation in the cortex of Pinus thunbergii on early invasion by the pinewood nematode

The distribution of cortical resin canals and periderm formation in the cortex of Pinus thunbergii was studied in relation to early invasion of the pinewood nematode, Bursaphelenchus xylophilus. Nematode invasion was restricted in stem cuttings of P. thunbergii in which periderm closed cortical resin canals. Early invasion of the nematodes was also restricted in stem cuttings where wound periderm had formed in response to prior nematode inoculation. It was concluded that early invasion of pinewood nematodes in living bark tissue is restricted by periderm in mature stems and by wound periderm that had formed as the result of previous nematode infection.     

Responses of apple fruit size to tree water status and crop load

The combined effects of irrigation rate and crop load on apple yield and fruit size were examined in two commercial apple orchards (cv. Golden Delicious) in a semi-arid zone. The irrigation rates applied were 1, 3 and 7 mm day(-1), and the two fruit thinning treatments involved adjusting crop load to 100 and 300 fruits per tree at Ortal and 50 and 150 fruits per tree at Matityahu. Unthinned trees served as the control. The fruit from each tree was picked separately, and fruit size distribution was determined with a commercial grading machine. Midday stem water potentials varied from -0.9 to -2.8 MPa, crop load varied from 80,000 to 1,900,000 fruit ha(-1) and crop yield varied from 10 to 144 Mg ha(-1). Midday stem water potential decreased with increasing crop load in all irrigation treatments at Matityahu, but only in the 1 mm day(-1) treatment at Ortal. The extent of the lowering of midday stem water potential by crop load decreased with increasing soil water availability. At both orchards, a similar response of total crop yield to crop load on a per hectare basis was observed. Mean fruit mass and relative yield of fruit > 70 mm in diameter increased with midday stem water potential, with the low crop loads having similar but steeper slopes than the high crop load. The responses of mean fruit mass and relative yield of fruit > 70 mm in diameter to midday stem water potential were similar at both orchards, perhaps indicating that thresholds for irrigation scheduling are transferable to other orchards within a region. Factors that may limit the transferability of these thresholds are discussed.