Hevea Research Articles

Evaluation of Bacillus subtilis Czk1 Metabolites by LC–MS/MS and Their Antifungal Potential against Pyrrhoderma noxium Causing Brow Rot Disease

Brown rot disease caused by Pyrrhoderma noxium is a widespread disease that severely affects the roots of rubber trees (Hevea brasiliensis Muell. Arg.). The economic losses, along with environmental and health problems arising from the use of disease control chemicals, have raised the interest of scholars to explore the use of biological control agents for the effective control of fungal pathogen P. noxium. Here, the inhibition effect of the culture filtrate of B. subtilis Czk1 on P. noxium was demonstrated. The findings indicate that the antifungal activity of this strain is mediated wholly or partly by compounds produced in the culture filtrate. The combined use of liquid chromatography–tandem mass spectrometry and antifungal activity assays rapidly identified compounds produced by B. subtilis Czk1. Metabolic profiles were assessed and used to identify major metabolites based on the scores of variable importance in the projection and the plot scores of principal component analysis. A total of 296 differential metabolites were screened, including 208 in positive ion mode and 88 in negative ion mode. Two key metabolites, diacetyl and trans-2-octenoic acid, were screened from 29 metabolites by antifungal activity assays. The median effective concentration (EC50) of trans-2-octenoic acid and diacetyl were 0.9075 mg/mL and 4.8213 mg/mL, respectively. The antifungal metabolites can disrupt the internal structure of the pathogenic fungal mycelium, thereby impeding its growth. This study is expected to contribute to the existing knowledge of Czk1-produced metabolites and their future antifungal applications. This study is also expected to provide a new biopreservative perspective on unexplored antifungal metabolites produced by Czk1 as a biocontrol agent.

Morphophysiological indicators applied for the selection of different genotypes of Hevea spp. during germination and post-germination

We investigate and characterize the morphophysiological changes related to germination and the initial growth and development of seedlings of wild and cultivated genotypes of the genus Hevea spp. in finding to add value to new clones. Seeds from six genotypes ( H. brasiliensis (Willd. Ex A. Juss) Müll. Arg, H. guianensis Aubl., H. spruceana (Benth.) Müll. Arg., RRIM 600, Fx 3844, and IAN 873) were sterilized, and their imbibition curve, germination parameters, and initial seedling growth were characterized. In parallel, the morphology of the germination and post-germination stages was monitored from seeds germinated in washed sand. Morphological differences in the seeds/embryos, different strategies in the imbibition process, emergence, and initial seedling growth were observed. The species H. guianensis and H. spruceana showed the greatest differences in size, shape, and color of the seeds/embryos and initial seedling growth. The characteristics of the seed coat patterns, the seedling imbibition, growth, and development processes can serve as morphophysiological markers for genotype identification and selection. This is the first morphophysiological study of seeds and seedlings of wild and cultivated genotypes of species of the genus Hevea. We conclude that there is considerable phenotypic variability among species of the Hevea genus regarding seed and seedling morphophysiology, which can be explored in the rubber tree breeding programs.

Comparison of Different Important Predictors and Models for Estimating Large-Scale Biomass of Rubber Plantations in Hainan Island, China

Rubber (Hevea brasiliensis Muell.) plantations are among the most critical agricultural ecosystems in tropical regions, playing a vital role in regional carbon balance. Accurate large-scale biomass estimation for these plantations remains a challenging task due to the severe signal saturation problem. Recent advances in remote sensing big data, cloud platforms, and machine learning have facilitated the precise acquisition of key physiological variables, such as stand age (A) and canopy height (H), which are critical parameters for biomass estimation but have been underutilized in prior studies. Using Hainan Island—the second-largest rubber planting base in China—as a case study, we integrated extensive ground surveys, maps of stand age and canopy height, remote sensing indicators (RSIs), and geographical and climate indicators (ECIs) to ascertain the optimal method for estimating rubber plantation biomass. We compared different inputs and estimation approaches (direct and indirect) using the random forest algorithm and analyzed the spatiotemporal characteristics of rubber plantation biomass on Hainan Island. The results indicated that the traditional model (RSIs + ECIs) had low accuracy and significant estimation bias (R2 = 0.24, RMSE = 38.36 mg/ha). The addition of either stand age or canopy height considerably enhance model accuracy (R2 = 0.77, RMSE ≈ 21.12 mg/ha). Moreover, incorporating the DBH obtained through indirect inversion yielded even greater predictive accuracy (R2 = 0.97, RMSE = 7.73 mg/ha), outperforming estimates derived from an allometric equation model input with the DBH (R2 = 0.67, RMSE = 25.43 mg/ha). However, augmenting the model with stand age, canopy height, or their combination based on RSIs, ECIs, and DBH only marginally improved the accuracy. Consequently, it is not recommended in scenarios with limited data and computing resources. Employing the optimal model, we generated biomass maps of rubber plantations on Hainan Island for 2016 and 2020, revealing that the spatiotemporal distribution pattern of the biomass is closely associated with the establishment year of the rubber plantations. While average biomass in a few areas has undergone slight decreases, total biomass has exhibited significant growth, reaching 5.46 × 107 mg by the end of 2020, underscoring its considerable value as a carbon sink.

Inventarisasi Tumbuhan Famili Euphorbiaceae Di Sekitar Herbarium Bandungense Sith ITB Jatinangor

Euphorbiaceae is an Angiosperm plant which has several varieties with one of the highest number of species. This plant is useful in industry and medicine. Characteristic of this plant has a gummy stem. This observation aims to determine the types of plants in the Euphorbiaceae family around the Bandungsense Herbarium SITH ITB Jatinangor on June 6 2023. Observations were carried out using the survey method and analyzed descriptively qualitatively. From the observations, it was found that 10 plant species belong to the Euphorbiaceae family, namely Acalypha siamensis, Euphorbia milli, Euphorbia hirta, Acalypha indica, Hevea brasiliensis, Phyllanthus urinaria, Phyllanthus niruri, Excoecaria agallocha, Euphorbia thymifolia Linn and Manihot esculenta. The results of the observations explain the characteristics of each plant, accompanied by personal documentation of the observations.

Application of Microgranule from IAA Producing-Endophytic Bacterial as Biofetilizer on Rubber Plants (Hevea brasiliences Muell. Arg.)

Rubber plant (Hevea brasiliensis Muell.Arg) is the main commodity of plantations, some of whose products are exported and some to meet domestic needs as raw materials for industrial purposes. Purpose on research diversity and crateristics of endophytic bacteria producing hormone IAA from rubber plants. Then the effectiveness treatment of microgranules addition and immersion of  endophite bacterial suspension and rubber seed soaking suspension to spur the growth of rubber plants. This research was conducted using the factorial CRD (Completely Randomized Design) method consisting of 16 treatments with 2 replications. The first factor was immersion of  endophite bacterial suspension consisting of R0 = 0 hours; R1 = 12 hours; R2 = 24 hours and R3 = 36 hours and the second factor was the addition of microgranules consisting of  J0 = 0 gr; J1 = 10 gr; J2 = 15 gr; J3 = 20 gr. The results of this study showed that the results on the isolation of endophite bacteria from the tea plant from the roots and stems of the tea plant yielded 3 isolates from plant roots and 2 isolates from plant stems. For IAA levels, the five isolates were positive. The use of endophytic bacteria as an alternative biofertilizer has a significant effect on the parameters observed

Large Scale Hevea brasiliensis Plantation Impact on Non-Human Primate and Floral Diversity in Khowai District of Tripura

Over the past three decades, a large proportion of forest area in Khowai district of Tripura has been converted into a rubber plantation (Hevea brasiliensis) area. There is less information about the deleterious effect of such changes on non-human primate populations and plant diversity. To address this deficit, line transect and quadrat sampling programs were carried out in Khowai district of Tripura with the purpose of comparing non-human primate species diversity, number of individual primate species observed and also plant species diversity observed in the rubber plantation area and nearby forest area. Less number of non-human primate was observed in the rubber plantation area than in the forest area and individual numbers of tree, shrub and herb species were found to be maximum in the nearby forest area than in rubber plantation area. In shrub layer Shannon and Simpson diversity index were higher in the forest area, whereas in herb layer, Shannon index was lower and Simpson index was higher in rubber plantation area. From this study it was divulge that, rubber plantation have harmful impact on non-human primate and plant species.

Lightweight Flame-retardant Material Reinforced with Hevea Brasiliensis Ash Intumescent Agent

Flame retardant materials play an important role in many building construction components. The ability of building components to resist fire is crucial to the safety and well-being of the occupants. This research examines a lightweight flame-retardant material-Vermiculite (V) reinforced with a renewable Hevea Brasiliensis Biomass Ash Intumescent Agent (HBAIA) in different compositions. Four specimens of vermiculite reinforced with HBAIA (V/HBAIA) with standard size 200 mm x 200 mm x 10 mm (W x Lx H) were fabricated for investigations. All V/HBAIA specimens were assessed in terms of their density, fire-resistant, fire endurance and smoke, char surface morphology, and flexural toughness. Data disclosed V/HBAIA-2 with the composition of 90% vermiculite reinforced with 10% HBAIA obtained the most prominent outcomes in overall. V/HBAIA-2 attained the lightest density of 37.5 kg/m3 and weight of 0.20 kg, with lowest end temperature of 122 °C after exposure to one-hour of 1000 °C fire. This indicated the best fire-resistant performance in V/HBAIA-2. No structural deformation and only mild smoke and odor were observed in V/HBAIA-2 during the fire endurance examination. V/HBAIA-2 was able to resist the maximum loading force of 67.4 N before and 52.5 N after the fire resistant, with the higher flexural toughness value of 1.47 MPa. Scanning electron microscopy revealed a more uniform, denser, closely connected air cavities char cell quality in V/HBAIA-2 explained its superior outcomes in fire-resistant and flexural toughness as compared to the rest of specimens.

Strategic revamping of natural rubber (Hevea brasiliensis) production system: Implications for livelihood sustainability in Delta state, Nigeria

Rubber industry in Nigeria is a source of livelihood to many people (producers and marketers)but a recent trend shows a fast disappearing rubber industry. The economic risks associated with disappearing rubber plantations is a serious challenge to individuals and societies as the natural, social and economic benefits of the industry are gradually eroded. Revamping the rubber plantation will restore and sustain the livelihood of the stakeholders in the industry. This study therefore examined the strategic revamping of the disappearing rubber industry and implications for livelihood sustainability in Delta State, Nigeria. A multi-stage sampling procedure was adopted in selecting 480 respondents for the study. Structured questionnaire was used to collect primary data. Collected data were analyzed with parametric and non- parametric statistical tools. Such as mean percentage, standard deviation, frequency distribution table. Logit regression model was used to analyze the factors that influence farmers’ probability to revamp natural rubber production. The finding shows that majority of the rubber farmers (85.38%) were old (51 – 70 years), cultivated between 0.5 and 1.0 hectares (small-scale production with large family size (above 5 persons) About 76.70% of rubber farmers expressed willingness to revamp rubber plantations. Identified livelihood capitals could significantly enhance the possibility of revamping rubber production system. Subsidizing the cost of relevant inputs (seedlings), discovery of foreign markets for rubber and large scale acquisition of land by corporate organization for rubber farming were the significant strategies identified and recommended for revamping rubber industry in Delta state, Nigeria. This study has expanded the frontier of literature on rubber by emphasizing that revamping rubber production has implications for livelihood sustainability for rubber farmers and marketers in Nigeria.

Improvement of the soil quality under intercropped conilon coffee (Coffea canephora P.) in the coastal tablelands of Southeast Brazil

The objective of this study was to evaluate the physical-hydrological and chemical properties and organic carbon stock of soil under intercropped conilon coffee (Coffea canephora P.) and in full sun in the coastal tablelands of Espírito Santo, Brazil. The treatments evaluated were coffee intercropped with rubber tree (CR) and in full sun (FS) in the area 1; coffee intercropped with papaya (CP) and in full sun (FS) in the area 2; coffee intercropped with coconut (CC), in full sun (FS), and an area of ​​native vegetation (NV) in the area 3. The physical and chemical properties of the soil and its organic carbon stocks were measured in layers of 0-0.4 m. In area 1, CR showed lower soil bulk density and temperature, and higher total porosity and macroporosity. In area 2, CP presented higher available water capacity and soil water content, better soil fertility, and lower soil temperature. In area 3, CC presented higher total porosity, available water capacity, and soil organic carbon stock. NV presented physical and chemical properties of soil that limit the agricultural development of the crops. Conilon coffee plantations can improve the physical-hydrological and chemical quality of soil compared to cultivation in full sun and native vegetation in the coastal tablelands, which varies according to the intercropped culture.

NUTRIENT MANAGEMENT FOR RUBBER PLANTATION USING GOAL PROGRAMMING

: Farm management must have proper planning on the resources such as fertiliser, labour, water and pesticide. Fertiliser provides healthy growth to the plant. It is one of the important resources the farm needs. Thus, the usage and allocation of fertilisers must be managed wisely to avoid wastage that incurs costs. This paper presents a case study which focuses on the nutrient management of rubber plantations. The main objective is to minimise the cost of chemical fertilisers used to plant rubber. Besides, the sub-objectives are to determine the best weight combination for fertilisers and calculate the mass per hectare of Nitrogen, Phosphorus, and Potassium needed for the rubber trees. The goal programming approach has been applied to solve the problem. In the model formulation, there are seven decision variables representing chemical fertilisers, while the constraints are the cost of chemical fertilisers and the requirement of the upper and the lower limit of nutrients in the chemical fertilisers. Results indicate that this method can meet all the goals expected. In conclusion, this study shows that goal programming is suitable for modelling plant input, cost and constraint of rubber farm management.

Cloning and Functional Analysis of the VfRR17 Gene from tung tree (Vernicia fordii).

Tung tree (Vernicia fordii) is one of the four major woody oilseed species in China. However, its fruit yield is severely hampered by the low number of female flowers and the imbalanced male-to-female flower ratio, which is a problem that restricts the development of the oilseed industry. Previous research has demonstrated that the exogenous application of cytokinins can significantly augment the number of female flowers, although the underlying regulatory mechanism remains elusive. To elucidate the involvement of VfRR17, a member of the A-type ARRs family, in the exogenous cytokinin regulation of flower sexual differentiation in tung tree, this study conducted a comprehensive bioinformatic analysis of the physicochemical properties, structural characteristics, and evolutionary relationships of the protein encoded by VfRR17. Additionally, gene function analysis was performed using subcellular localization, qRT-PCR, and genetic transformation techniques. The findings revealed that the VfRR17 gene's coding region spanned 471 bp, encoding an unstable protein of 156 amino acids with a relative molecular mass of 17.4 kDa. Phylogenetic analysis demonstrated a higher similarity between VfRR17 of the tung tree and the RR17 gene of Jatropha curcas, Ricinus communis, Hevea brasiliensis, and other species within the Euphorbiaceae family compared to other species, with the greatest similarity of 86% observed with the RR17 gene of Jatropha curcas. The qRT-PCR analysis indicated that VfRR17 exhibited high expression levels during the early stage of tung tree inflorescence buds following 6-BA treatment, peaking at 24 h and displaying a 3.47-fold increase compared to that at 0 h. In female and male flowers of the tung tree, the expression in female flowers during the 1 DBF period was significantly higher than in male flowers, exhibiting a difference of approximately 47.91-fold. Furthermore, notable differential expression was observed in the root, leaf, and petiole segments of the tung tree under low-temperature stress at the 12-h time point. In transgenic Arabidopsis, the VfRR17 lines and wild-type lines exhibited significantly different flowering times under an exogenous 6-BA treatment at a concentration of 2 mg/L, with the VfRR17 lines experiencing an 11-day delay compared to the wild-type lines. Additionally, the number of fruit pods in VfRR17 transgenic Arabidopsis lines was significantly reduced by 28 compared to the wild-type lines at a 6-BA concentration of 3 mg/L. These findings suggest that VfRR17 likely plays a critical role in regulating flower development in response to exogenous 6-BA, providing valuable insights into the mechanisms underlying exogenous 6-BA-mediated regulation of female flower development in the tung tree.

Rat Taro Extract (Typhonium flagelliforme (Lodd.)) as A Biofungicide Against the Cause of Leaf Fall (Pestalotiopsis sp.) on Rubber Plants (Hevea brasiliensis)

Typhonium flagelliforme or known as rat taro is a herbaceous plant that belongs to the taro tribe. The results of the phytochemical analysis of the leaves and tuber extracts of rat taro are known to contain secondary metabolite compounds belonging to the class of flavonoids, alkaloids, triterpenoids, steroids, saponins, and tannins which act as antimicrobials. This study aims to determine the effectiveness of leaf, stem and tuber extracts of rat taro (Typhonium flagelliforme (Lodd)) as a biofungicide against the cause of leaf fall (Pestalotiopsis sp.) on rubber plants (Hevea brasiliensis). Leaf samples came from rubber plants at PTPN III Karet Sei Putih, Galan District, Deli Serdang Regency, North Sumatra. Pestalotiopsis sp. was isolated from plant parts showing leaf fall symptoms. Pieces of rubber leaves infected with Pestalotiopsis sp. was grown on PDA media in a petri dish and incubated for ±7 days at room temperature 26–28oC. After incubation, microscopic identification of the conidia of the fungus was carried out. In vitro test of the inhibition power of extracts of leaves, stems and tubers of rat taro against the fungus Pestalotiopsis sp. was carried out in a petri dish using the fungus culture method. The results of the phytochemical screening showed that the leaf, stem and tuber extracts of rat taro contained chemical compounds of flavonoids, tannins, saponins, alkoloids, and steroids/triterpenoids. The results showed that the leaves, stems and tuber extracts of rat taro (T. flagelliforme L.) have potential as biofungicides, K13 treatment of tuber extract of rat taro (Typhonium flagelliforme L.) 9% was the best treatment which could inhibit the growth of Pestalotiopsis sp.

Utilization of Forage Crops as an Effective and Eco-friendly Method for Weed Growth Control and Distribution in an Immature Rubber Plantation

Rubber plantation, especially in the immature phase, is usually infested by various local weed species in the inter-row spaces of the rubber trees. This study aimed to evaluate the distribution of weed species and the growth and yield of forage crops for weed control and management in an immature rubber plantation. The field study was conducted with four treatments of forage crops. The first treatment was a control plot in which local weeds were growing naturally without forage crops. The plot was compared with the other three immature plots wherein native tropical carpet grass (Axonopus compressus), native whip grass (Hemarthria compressa) and high productive yield ruzi grass (Brachiaria ruziziensis) were planted, respectively, in the inter-row of the rubber trees. The study period was split into four seasons: S0 – January to June 2016; S1 – July to September 2016; S2 – October to December 2016; and S3 – January to March 2017. Results showed that three families of narrow-leaf and nine families of broad-leaf weeds were found in the study area. A large number of common weed families were observed more in the S3 than those in other seasons. Moreover, all forage crops were effective in suppressing weeds, with ruzi grass demonstrating the highest level of competitiveness and yield among the native forage crops reaching 1.50 Mg ha-1 in the S3. Therefore, implementing an indirect weed control approach using forage crops in rubber plantations could serve as a sustainable and environmentally friendly alternative to chemical herbicides.

Back to the 'roots' of research: a hypothesis-driven approach provides predictive understanding of plant-herbivore-microbe interactions.

This article is a Commentary on Böttner et al. (2023), 239: 1475–1489.

Short-Term Effects of Bokashi Fertilizer with Reduced NPK Fertilization on Soil Fertility, Growth, and Yield of Rubber Trees

Rubber is currently the second major industrial crop in Malaysia after oil palm. The use of bokashi fertilizer (BF) on industrial crops is still not popular, and farmers rely mostly on chemical fertilizers (CFs) that are costly and hazardous to the environment. This research was conducted at Hevea plantation, Universiti Putra Malaysia, between August 2020–October 2021. The study was to assess the short-term effects of BF with reduced NPK fertilization on soil fertility, growth, and yield of rubber. Seven treatments (T) were involved. T1, T2, and T3 denote 4, 8, and 12 kg BF per pit. T4 was 1 kg NPK as control, whereas T5, T6, and T7 denote 4, 8, and 12 kg BF + 500 g NPK per pit, respectively. The variables observed included total nitrogen (TN%), total phosphorus (TP%), organic carbon (OC%), organic matter (OM%), exchangeable cations, microbial counts, tree girth, and dry rubber yield. The major findings indicated that applying 12 kg BF has raised the soil’s TN%, OC%, and OM% by 165, 171.4, and 172.0%, respectively, compared to NPK control. Also, adding 4 kg BF + 500 g NPK has increased the soil’s cation exchange capacity and TP% values by 107.8 and 42.9%, respectively, compared to the control. Adding sole bokashi increased the bacterial population by 22.2–133.3%. Rubber yield was better on trees treated with 12 kg BF, though this did not differ significantly from other treatments. Therefore, applying 12 kg BF or 4 kg BF + 500 g NPK can improve soil fertility and save costs from using inorganic fertilizer by at least 50%.

Functionalization of carbon from rubber fruit shells (Hevea brasiliensis) with silane agents and its application to the adsorption of bi-component mixtures of methylene blue and crystal violet.

In this research, activated carbon was obtained from rubber fruit shells (ACRPs). The obtained activated carbon (ACRPs) was modified by magnetite particle coating and silanization with triethoxyiphenylsilane (TEPS) to produce a new magnetic adsorbent (ACRPs-MS). The affinity of as-prepared adsorbent (ACRPs-MS) toward methylene blue (MB) and crystal violet (CV) dyes was tested in mono-component and bi-component solutions. Structural characterization proves the success of the magnetite coating process and the silanization of ACRPs. In the infrared (IR) spectroscopy spectrum of ACRPs-MS, Si-O-Fe and Si-O-Si bonds were identified, which indicated the presence of magnetite and silane. This is also supported by the elemental composition contained in the energy-dispersive X-ray (EDX) diffractogram. In addition, the presence of the porous structure of the surface of the material and the increase in the specific surface area increase the accessibility of contaminants such as MB and CV dyes to be adsorbed to the ACRPs-MS adsorption site effectively. The experimental results showed that the adsorption of mono-component MB and CV dyes by ACRPs-MS was optimum at pH8 and an interaction time of 60min. The adsorption kinetics of mono-component MB and CV dyes by ACRPs-MS tended to follow pseudo-second-order kinetics (PSO) models with PSO rate constant (k2) values of 0.198 and 0.993gmg-1min-1, respectively. The adsorption of MB and CV dyes by ACRPs-MS in a bi-component mixture tends to follow the Langmuir isotherm model with adsorption capacity (qm) values of 85.060 and 90.504mgg-1, respectively. Analysis of adsorption data on the bi-component mixture between MB and CV by ACRPs-MS with the Langmuir isotherm equation for a binary mixture resulted in qm of 22.645 × 10-3mmol equiv g-1. ACRPs-MS material can be used repeatedly five times with adsorption ability > 80%. Desorption of MB and CV dyes was carried out using 0.05M HCl solution. ACRPs-MS material was able to adsorb MB and CV dyes with a large adsorption capacity and could be used in repeated adsorption. Thus, it can be stated that ACRPs-MS can be used as an effective adsorbent for MB and CV dyes, either singly or in a bi-component mixture.

Front Cover Image

The cover image is based on the Original Article Single-cell transcriptomic analyses reveal cellular and molecular patterns of rubber tree response to early powdery mildew infection by Xiaoyu Liang et al., https://doi.org/10.1111/pce.14585.

Characteristics of Physical, Chemical, and Organoleptic Properties of Gulai, Kalio, and Rendang from Rubber Seeds (Hevea Brasiliensis) as Traditional Plant-based Food

The study aimed to determine the physical, chemical, organoleptic characteristics and safety of rubber seeds (Hevea brasiliensis) which were processed into gulai, kalio, and rendang. This research used a descriptive exploratory method to determine the differences in rubber seeds’ physical, chemical, and organoleptic properties. The treatments in this study were processing rubber seeds into gulai with a cooking time of 1 hour, kalio with a cooking time of 2 hours, and rendang with a cooking time of 3 hours. Physical analysis showed the highest hardness value was in processing rubber seeds into rendang 31.03 N/cm2. Chemical analysis of processed rubber seed products for the highest water content in rubber seed gulai 59.25%, the highest ash content in rubber seed rendang 6.78%, the highest protein content in rubber seed gulai 8.99%, the highest fat content in rubber seed rendang 38.84%, the highest carbohydrate content in rubber seed rendang 16.29%, the tallest free fatty acid number in rubber seed rendang 0.4%, the peroxide value was not detected in each treatment product. The highest cyanide acid was in rubber seed gulai 10.76 mg/kg. Based on the organoleptic test, rendang rubber seed is the most preferred processed rubber seed product from aroma, color, texture, and taste.

Encouraging the reconversion of rubber plantations by developing a combined payment system

Rubber (Hevea brasiliensis) has been introduced to Southeast Asia for over a century. In various regions throughout Southeast Asia, over the past two decades, natural tropical forests have rapidly been converted into rubber monoculture. To encourage the reconversion of rubber plantations back to close-to-nature rainforests, we developed a theoretical combined market and government payment system. To evaluate the potential impacts of the system, we carried out a simulation study from 2020 to 2050 in Xishuangbanna, Southwest China. The results suggest that the payment system may encourage a total reconversion area of 198,490 ha with a total government payment of US$0.377 billion in net present value (NPV) by 2050. The total carbon sequestration benefit resulting from the replacement of rubber plantations would be 14.83 million tons of carbon over the modelled period. Sensitivity analyses revealed that rubber price was the most sensitive factor on the total NPV of compensatory payments, and followed by the discount rate. The rubber price increased by 96.8% could enhance the compensatory payments in NPV by 272%, whereas a 10% decrease in the discount rate resulted in a 18.9% increase of the compensatory payments in NPV. This new integrated payment system holds the potential of stimulating restoration of cash crop monoculture-dominated landscapes to multifunctional forest ecosystems.

Study of Five Clones with Combinations of Growth Regulators Based on Growth and Anatomical Characteristics of Rubber Plant (Hevea brasiliensis L.)

As an export commodity, rubber is a major contributor to Indonesia's foreign exchange. Regarding the increase in rubber production, a study on combinations of growth regulators and rubber clones has been carried out based on plant growth and anatomical characteristics during the immature plant period. This research is conducted for eighteen months at the KSO Karang Inong plantations, PTPN-I, and PTPN-III, East Aceh District, using five clones. This study adopts a nested design with three factors: clones, Growth Regulators (GRs), and paclobutrazol. The clones used are PB 260, IRR 104, IRR 112, IRR 39, and 105. The GRs combination factor between IAA and Kinetin consists of seven levels and three levels of paclobutrazol. The results show that the rubber clones PB260 and IRR105 give higher stem girth and plant height than the other clones when applied with GRs at six different levels. The most expansive leaf area is found in clone IRR 104 compared to other clones. In addition, paclobutrazol affects plant height. Applying paclobutrazol can reduce plant height for all clones but increases stem girth, skin thickness, number and diameter of latex vessels, and total chlorophyll at 46 months after treatment.