Effect of ultrasonic wave on latex production and quality of rubber tree

The effects of ultrasonic wave on tapping surface of ‘PR107’ rubber tree were studied. Daily production and cumulative production of latex were measured to estimate the effects of ultrasonic wave on latex production. The solid substance content, dry rubber content and mechanical stability of latex were determined to study the effects of ultrasonic wave on latex quality. Results showed that ultrasonic wave could increase both daily and cumulative production of latex and maintain latex basic quality. The daily production of latex was increased and appeared two peaks both in the ultrasound-treated rubber tree and the one with no treatment. The first peak appeared on the fifth day, and the latex production by ultrasound was 212.34 ml and the control was 141.75 ml The second peak appeared with the production 266.59 ml on the seventeenth day by ultrasound, while the control appeared on the thirteenth day with production of 193.5 ml. The latex cumulative production of ultrasound-treated trees was 209.56 ml higher than that of control in one month. There was little change in solid substance content and dry rubber content between different ultrasonic time. The best mechanical stability of latex was obtained by ultrasound-treating the rubber tree for 4-6 min. it was proved that the ultrasound was helpful in improving the latex production and quality. The application of ultrasonic wave on rubber tree is novel, and its mechanism is worth further research.

Primary prevention of latex related sensitisation and occupational asthma : a systematic review

Eight primary prevention intervention studies on natural rubber latex (NRL) published since 1990 were identified and reviewed. This is the largest evidence base of primary prevention studies for any occupational asthmagen. Review of this small and largely observational evidence base supports the following evidence statement: Substitution of powdered latex gloves with low protein powder‐free NRL gloves or latex‐free gloves greatly reduces NRL aeroallergens, NRL sensitisation, and NRL‐asthma in healthcare workers. Evidence in support of this statement is ranked SIGN level 2+, referring to well conducted case‐control or cohort studies with a low risk of confounding, bias, or chance and a moderate probability that the relationship is causal. Substitution of powdered latex gloves with low protein powder‐free NRL gloves or latex‐free gloves promises benefits to both workers' health and cost and human resource savings for employers. This message should be broadly disseminated beyond the hospital sector to include other healthcare settings (such as aged care facilities) as well as food service and other industries where latex gloves might be used.

Variation of phloem turgor pressure in Hevea brasiliensis: An implication for latex yield and tapping system optimization

Phloem turgor pressure (PTP) is the initial driving force for latex flow after a rubber tree is tapped and therefore plays an important role in rubber tree latex production. Variation in PTP with rubber tree clone, age, yield potential and commonly used Ethrel (an ethylene releaser) stimulation have, however, not been comprehensively studied to date. The aim of this study was to investigate these relations and examine whether PTP can be used as an index for rubber tree clone assessment and tapping system optimization. The results showed that: (1) the daily change of PTP in the foliation season suggests that a high PTP can ensure a high latex yield and tapping could be moved forward to midnight or earlier in the night; (2) the decrease of PTP from the basal to distal stem indicates the benefit of a controlled upward tapping system; (3) the logarithmic increase in PTP with rubber tree planting age and age-based mean girth suggests that the preferred age for the commencement of rubber tree tapping is eight years; (4) the change of PTP with regenerated bark age suggests that the regenerated bark could be exploited again after the second year; (5) PTP is positively related to the yield potential of rubber tree clones; (6) although Ethrel stimulation could not significantly increase the initial PTP of a rubber tree, it delays the recovery of PTP after tapping. Therefore, PTP is an indicator of rubber tree latex yield and can be used for tapping system optimization. © 2014 Elsevier B.V.

Latex dilution reaction during the tapping flow course of Hevea brasiliensis and the effect of Ethrel stimulation

The latex dilution reaction during the tapping flow course has been well documented and associated with the facilitation of tapping latex flow. However, its underlying mechanism has not experimentally examined. The latex total solid content, osmotic potential and phloem turgor pressure change during the tapping flow course were simultaneously measured to investigate the cause of water movement during the tapping flow course. It was found that there are three different stages for the laticifer water equilibrium during the tapping flow course. The tapping-induced rapid turgor pressure drop is the cause of the first stage water influx into laticifers, while osmoregulation prevails during water exchange in the second and third stages of tapping flow. Meanwhile, aquaporin expressions were, for the first time, investigated during the tapping flow course. The rapid transcript up-regulation of HbPIP1, HbPIP2;1 and HbPIP2;3 contributes to the latex dilution reaction. However, their activity gating cannot be ruled out. Ethrel stimulation can significantly dilute the corresponding latex fractions during the tapping flow course due to its up-regulations of HbPIP1, HbPIP2;1 and HbPIP2;3. Nevertheless, the latex dilution reaction pattern for the Ethrel treated trees did not change, except for a lower degree of dilution compared with the un-treated trees. All these results suggest that both phloem turgor pressure and aquaporins are involved in the latex dilution reaction during the tapping flow course.

Regulation of HbPIP2;3, a latex-abundant water transporter, is associated with latex dilution and yield in the rubber tree (Hevea brasiliensis Muell. Arg.)

Rubber tree (Hevea brasiliensis) latex, the source of natural rubber, is synthesised in the cytoplasm of laticifers. Efficient water inflow into laticifers is crucial for latex flow and production since it is the determinant of the total solid content of latex and its fluidity after tapping. As the mature laticifer vessel rings are devoid of plasmodesmata, water exchange between laticifers and surrounding cells is believed to be governed by plasma membrane intrinsic proteins (PIPs). To identify the most important PIP aquaporin in the water balance of laticifers, the transcriptional profiles of ten-latex-expressed PIPs were analysed. One of the most abundant transcripts, designated HbPIP2;3, was characterised in this study. When tested in Xenopus laevis oocytes HbPIP2;3 showed a high efficiency in increasing plasmalemma water conductance. Expression analysis indicated that the HbPIP2;3 gene was preferentially expressed in latex, and the transcripts were up-regulated by both wounding and exogenously applied Ethrel (a commonly-used ethylene releaser). Although regular tapping up-regulated the expression of HbPIP2;3 during the first few tappings of the virginal rubber trees, the transcriptional kinetics of HbPIP2;3 to Ethrel stimulation in the regularly tapped tree exhibited a similar pattern to that of the previously reported HbPIP2;1 in the virginal rubber trees. Furthermore, the mRNA level of HbPIP2;3 was associated with clonal yield potential and the Ethrel stimulation response. Together, these results have revealed the central regulatory role of HbPIP2;3 in laticifer water balance and ethylene stimulation of latex production in Hevea.

In situ synthesis of natural rubber latex-supported gold nanoparticles for flexible SERS substrates

Natural rubber latex (NRL) from Hevea brasiliensis was used as a matrix to synthesize gold nanoparticles (AuNPs), leading to an organic-inorganic hybrid latex of NRL-supported AuNPs (AuNPs@NRL). The in situ and environmentally friendly preparation of AuNPs in an NRL matrix was developed by thermal treatment without using any other reducing agents or stabilizers because natural rubber particles and non-rubber components present in serum can serve as supporters for the synthesized AuNPs. As a result, the nanosized and well-dispersed AuNPs not only are decorated on the surface of natural rubber particles, but also can be found in the serum of NRL. The size of the AuNPs presented in NRL matrix can be controlled by adjusting the concentration of NRL. Furthermore, the flexible surface-enhanced Raman scattering (SERS) substrates made from the AuNPs@NRL through vacuum filtration presented good enhancement of the Raman probe molecule of 4-mercaptopyridine and outstanding SERS reproducibility. The capability of synthesizing the bio-supported nanohybrid latex provides a novel green and simple approach for the fabrication of flexible and effective SERS substrates.

LC–MS and GC–MS metabolite profiling of nickel(II) complexes in the latex of the nickel-hyperaccumulating tree Sebertia acuminata and identification of methylated aldaric acid as a new nickel(II) ligand

Targeted liquid chromatography–mass spectrometry (LC–MS) technology using size exclusion chromatography and metabolite profiling based on gas chromatography–mass spectrometry (GC–MS) were used to study the nickel-rich latex of the hyperaccumulating tree Sebertia acuminata. More than 120 compounds were detected, 57 of these were subsequently identified. A methylated aldaric acid (2,4,5-trihydroxy-3-methoxy-1,6-hexan-dioic acid) was identified for the first time in biological extracts and its structure was confirmed by 1D and 2D nuclear magnetic resonance (NMR) spectroscopy. After citric acid, it appears to be one of the most abundant small organic molecules present in the latex studied. Nickel(II) complexes of stoichiometry NiII:acid = 1:2 were detected for these two acids as well as for malic, itaconic, erythronic, galacturonic, tartaric, aconitic and saccharic acids. These results provide further evidence that organic acids may play an important role in the transport and possibly in the storage of metal ions in hyperaccumulating plants.

Hydrangea-like multi-scale carbon hollow submicron spheres with hierarchical pores for high performance supercapacitor electrodes

Uniform hydrangea-like multi-scale carbon hollow submicron spheres (HCSSg) are fabricated by a simple hydrothermal method using glucose as carbon source and fibrous silicon dioxides spheres as shape guide. Structure characterization suggests that petal-like partially graphitized carbon nanosheets with the thickness of about 10 nm arranged in three dimensions (3D) to form the hydrangea-like hollow spheres (size ranging from 250 to 500 nm) with mesoporous channels, which can be conducive to be a high specific surface area (934 m2 g-1) and bulk density (0.87 cm g-3), hierarchical pores structure with good conductivity. As a result, the HCSSg has been demonstrated to be a supercapacitor electrode material with high gravimetric (386 F g-1 at 0.2 A g-1) and outstanding volumetric (335 F cm-3) capacitance, good rate capability and cycling stability with 94% capacitance retention after 5000 cycles in aqueous electrolytes, thus suggesting its application potential.

Ethephon increases rubber tree latex yield by regulating aquaporins and alleviating the tapping-induced local increase in latex total solid content

The concentration of phloem solute generally falls from leaves to roots. However, a local increase in latex total solid content (LILTSC) was identified near the tapping cut of rubber trees. To understand the mechanism of ethephon-stimulated latex yield, the formation and ethephon (an ethylene releaser) alleviation of the LILTSC near the tapping cut were examined. It was found that the LILTSC near the tapping cut of a tapped rubber tree was caused by the tapping-accelerated rubber biosynthesis which began following the first tapping and became significant after the fourth tapping. Ethephon stimulation markedly reduced the LILTSC. The latex yield change pattern upon ethephon stimulation was associated with the kinetic change of LILTSC and the decomposition dynamic of ethephon into ethylene. Once the LILTSC was reduced by ethylene release upon ethephon stimulation, the latex yield increased; however, when the ethylene release upon ethephon stimulation receded, the LILTSC was restored and the effect of ethephon stimulation dissipated. The reduction of LILTSC by ethephon stimulation could be ascribed to the translocation property of ethylene in plants and its regulation of aquaporins. Because maximum ethylene release upon tapping-cut-ethephon-application occured close to the tapping cut, the aquaporins were more up-regulated in this region, leading to a reduction of the LILTSC and an increase in latex yield. All these results suggest that the LILTSC near the tapping cut was caused by tapping; the ethephon-induced aquaporin up-regulation and LILTSC reduction are involved in the mechanism of ethephon-promoted latex yield.

Development of hyaline spheres in late auriculariae of sandfish, Holothuria scabra : is it a reliable indicator of subsequent performance?

This study assessed the influence of diet composition on hyaline sphere (HS) development in auricularia larvae of the sandfish, Holothuria scabra, and the subsequent relationships between the presence and size of hyaline spheres and competency through settlement and early juvenile performance. Two-day old larvae were fed one of three commercially available micro-algae diets that varied in their nutrient compositions: (1) Isochrysis sp. (Haptophyceae); (2) Pavlova sp. (Haptophyceae); and (3) Thalassiosira weissflogii (Bacillariophyceae) or a ternary combination of the three. There were positive significant correlations between HS development in late auriculariae on days 10, 11, 12 and 13 post-fertilisation, and the proportion of competent doliolariae on day 15, post-settlement size (day 21) and post-settlement survival (day 25). The dietary components that most strongly influenced these relationships were carbohydrates and the n-3 polyunsaturated fatty acids arachidonic acid (ARA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Our result confirm the strong relationship between HS formation in late auriculariae of sandfish and subsequent larval competency through settlement. As such, the presence and size of HS is a reliable indicator of subsequent performance for sandfish. Given that HS development was influenced by the nutrients available to sandfish auriculariae, there is clear opportunity for development of more appropriate diets for hatchery culture of this species that will improve HS formation and larval performance supporting improved hatchery production. Statement of relevance Our results have confirmed that for sandfish larvae, the presence and size of HS at the end of the auricularia stage, is indeed a reliable indicator of subsequent performance. Our results have also confirmed that HS formation and size is significantly influenced by the nutrient composition of the auricularia diet, and that there are significant positive correlations between HS formation and dietary levels of carbohydrate, EPA:DHA and EPA:ARA ratios. This information provides a strong basis for development of more appropriate diets for sandfish larvae that will improve HS formation and larval performance during hatchery culture and in turn improve hatchery production of this species.