Embryo culture is an efficient way to conserve a medicinally important endangered forest tree species Strychnos potatorum

The present study reports a protocol for germination of Strychnos potatorum （ver. Tel. Chilla） using zygotic embryo culture as an embryo rescue method. A 100% germination rate was obtained by culturing the embryos on full-strength Murashige and Skoog＇s medium （MS） containing 20 g/L sucrose in comparison to McCown and Lloyd＇s Woody Plant Medium （WPM）. Germination rates decreased when the sucrose concentration was lower or higher than 20 g·L-1 . WPM/MS medium containing glucose at levels 30, 20, 15 g·L-1 showed a smaller percentage of germination and at quarter strength, WPM/MS medium with glucose did not respond. Multiple shoot formation was found at 1.0 2.0 mg/L BAP; 3.0 mg/L Kn; 2.0 mg/L TDZ on MS medium with 20 g·L-1 sucrose. Germination rates improved when the embryos were placed upright （vertically） in the medium. The in vitro germinated seedlings were acclimatized in a walk-in-chamber and maintained in the green house with the survival rate of 65% 75%. These plants were transferred to the field and were found to be phenotypically normal, healthy and similar to donor plants. This protocol will be useful to overcome seed dormancy and for rapid multiplication and conservation of S. potatorum using zygotic embryo culture.

Effects of plant growth regulators, carbon sources and pH values on callus induction in Aquilaria malaccensis leaf explants and characteristics of the resultant calli

The endangered tropical tree, Aquilaria malaccensis, produces agarwood for use in fragrance and medicines. Efforts are currently un-derway to produce valuable agarwood compoundsn tissue culture. The purpose of this study was to develop an optimal growth medium, specif-ically, the best hormone combination for callus suspension culture. Using nursery-grown A. malaccensis, sterilized leaf explants were first incu-bated on basic Murashige and Skoog （MS） gel medium containing 15g/L sucrose and at pH 5.7. Different auxin types including 1-naphthaleneacetic acid （NAA）, 2,4-dichlorophenoxyacetic acid （2,4-D）, and indole-3-butyric acid （IBA）, were tested at various concentrations （0.55, 1.1 and 1.65 μM） using the basic medium. Leaf explants were incubated for 30 days in the dark. Callus induced by 1.1 μM NAA had the highest biomass dry weight （DW） of 17.3 mg;however the callus was of a compact type. This auxin concentration was then combined with either 6-benzylaminopurine （BAP） or kinetin at 0.55, 1.1, 2.2 or 3.3 μM to induce growth of friable callus. The 1.1μM NAA＋2.2μM BAP com-bination produced friable callus with the highest biomass （93.3mg DW）. When testing the different carbon sources and pHs, sucrose at 15g/L and pH at 5.7 yielded highest biomasses at 87.7mg and 83mg DW, respec-tively. Microscopic observations revealed the arrangement of the friable cells as loosely packed with relatively large cells, while for the compact callus, the cells were small and densely packed. We concluded that MS medium containing 15 g/L sucrose, 1.1 μM NAA ＋ 2.2 μM BAP hor-mone combination, and a pH of 5.7 was highly effective for inducing friable callus from leaf explants of A. malaccensis for the purpose of establishing cell suspension culture.

Soil ecosystem changes by vegetation on old-field sites over five decades in the Brazilian Atlantic forest

Vegetation types alter soil ecosystems by changing soil fauna community activities and soil physi-cal-chemical properties.However,it is unclear how tree species(natural forest,native and exotic tree plantations)promote changes in the soil ecosystem,and if these changes alter functional groups of soil fauna and ecosystem services.To determine the effects of five decades of old-field veg-etation on soil ecosystems in the Brazilian Atlantic Forest,field sampling of three ecosystems(exotic tree species Pinus elliottii Engelm.plantation,endangered tree species Arau-caria angustifolia(Bertol.)Kuntze plantation,and a natural ecosystem)were carried out,as well using bait-lamina tests and bioassays with collembolans,earthworms and seeds of Lactuca sativa L.Field sampling evaluated the soil fauna community and soil physical-chemical properties.The bait-lamina test in situ was carried out for 14-days to deter-mine fauna feeding activity,and the bioassays evaluated the reproduction of Folsomia candida,the avoidance of Eisenia andrei,and germination of L.sativa in the soil from each ecosystem.The results are:(1)vegetation type altered the soil fauna community composition;(2)soil fauna feeding was reduced in the plantations compared to the natural eco-system;(3)a physical barrier was created by recalcitrant litter that compromised fauna community structure and seed bank germination in situ;and,(4)changes in soil physical-chemical properties promoted decomposers.

Evaluating soil nutrients of Dacrydium pectinatum in China using machine learning techniques

Background: The accurate estimation of soil nutrient content is particularly important in view of its impact on plant growth and forest regeneration. In order to investigate soil nutrient content and quality for the natural regeneration of Dacrydium pectinatum communities in China, designing advanced and accurate estimation methods is necessary.Methods: This study uses machine learning techniques created a series of comprehensive and novel models from which to evaluate soil nutrient content. Soil nutrient evaluation methods were built by using six support vector machines and four artificial neural networks.Results: The generalized regression neural network model was the best artificial neural network evaluation model with the smallest root mean square error(5.1), mean error(-0.85), and mean square prediction error(29). The accuracy rate of the combined k-nearest neighbors(k-NN) local support vector machines model(i.e. k-nearest neighbors-support vector machine(KNNSVM)) for soil nutrient evaluation was high, comparing to the other five partial support vector machines models investigated. The area under curve value of generalized regression neural network(0.6572) was the highest, and the cross-validation result showed that the generalized regression neural network reached 92.5%.Conclusions: Both the KNNSVM and generalized regression neural network models can be effectively used to evaluate soil nutrient content and quality grades in conjunction with appropriate model variables. Developing a new feasible evaluation method to assess soil nutrient quality for Dacrydium pectinatum, results from this study can be used as a reference for the adaptive management of rare and endangered tree species. This study, however, found some uncertainties in data acquisition and model simulations, which will be investigated in upcoming studies.