Biogenic volatile organic compounds (BVOCs) are important secondary metabolites released by forest plants, playing a crucial role in plant growth, development and environmental regulation. This study focused on rubber trees (Hevea brasiliensis) widely cultivated in Hainan Island. Using dynamic headspace sampling coupled with thermal desorption-gas chromatography-mass spectrometry (GC-MS), we systematically analyzed the emission characteristics of BVOCs and the environmental influencing factors across rubber trees of different stand ages (5, 15, 20 and 25 years). The diurnal variation of BVOCs exhibited a unimodal curve, with peak emissions concentrated between 10:30 and 13:00. BVOC emission rates decreased significantly with increasing stand age (5 years >15 years >20 years >25 years), and emissions during the rainy season were significantly higher than those during the dry season. The diversity of monoterpenes (MTs), other terpenes (OTs) and oxygenated volatile organic compounds (OVOCs) decreased with stand age, while sesquiterpenes (STs) remained stable. BVOC emissions showed significant positive correlations with net photosynthetic rate, transpiration rate, and light intensity (P<0.05), with light intensity being the primary influencing factor. The effects of air temperature and humidity on BVOC emissions increased with stand age. This study elucidated the age-related effects and seasonal dynamics of BVOC emissions in rubber plantations, providing a scientific basis for assessing the ecological and environmental impacts of tropical artificial forests.

The identification and evaluation of superior germplasm are the foundation for the research on germplasm resources and breeding utilization. 45 citronella grass resources from Hainan, Fujian, Guizhou, Yunnan and other regions were assayed to evaluate the essential oil content. The agronomic traits, essential oil content and main components of essential oil of the resources at different cutting stages were analyzed in Kunming. The results showed that there were significant differences in total grass length, leaf length, leaf width, biological yield and essential oil content among different cutting periods and different materials. Correlation analysis between characteristic traits and essential oil content revealed that the essential oil content was significantly negatively correlated with leaf length and significantly positively correlated with leaf width. Systematic cluster analysis based on agronomic traits and essential oil content divided the resources into 5 groups. The Ⅰ group contained 36 materials, and all materials were identified as Cymbopogon citra=tus, The Ⅱ group had 4 materials, all in Cymbopogon winterianus. Cymbopogon caesius and Cymbopogon hamatulus were individually clustered into the Ⅳ and Ⅴ groups, respectively. A standard for identifying and grading superior germplasm oriented towards essential oil yield was established, and the 45 resources were divided into three grades, including 6 in the first grade, 18 in the second grade and 21 in the third grade. In addition, the analysis of essential oil content and main components of 16 germplasm in Yuanmou test region at 6 different periods showed that the accumulation of essential oil did not increase with the extension of planting time, and the contents of main components in essential oil also varied in different periods. Geraniol reached the highest value in January; Linalool had the highest content in March; Geranyl acetate peaked in September; Citronellyl acetate had the highest content in January, and β-myrcene was the highest in May. This study would provide a scientific basis for the identification and evaluation of superior citronella grass germplasm, breeding utilization, and the production and utilization of high-quality and high-yield raw materials.

Coconut water is sterile in the interior cavity of the coconut fruit. However, once the coconut is opened and repackaged, the coconut water beverage may become a breeding ground for bacteria and fungi, leading to the production of harmful mycotoxins. This study aimed to detect the usage of preservatives and sweeteners, also the levels of the common carcinogenic contaminant benzo[a]pyrene and harmful mycotoxins in bottled coconut water sold on the market. By using national standard methods, no preservative such as benzoic acid and sorbic acid, no sweetener sodium saccharin, and no contaminant benzo[a]pyrene were detected in this batch of coconut water beverages. This study also investigated the level of mycotoxins in bottled coconut water stored at low temperatures (4-8 ℃) for 21 days. No zearalenone (ZEN) or deoxynivalenol (DON) was detected in the coconut water stored at 4-8 ℃ for 21 days. During monitoring, the response signal for aflatoxin B₁ (AFT B₁) in one of the samples had an increasing trend with prolonged storage time but the level did not exceed the quantitative limit specified in the national standard method. Electron microscope observation of the bottled coconut water stored at low temperatures revealed a large number of moving microorganisms in 1-3 days, with the aerobic plate count increasing exponentially. After 21 days of low-temperature storage, infrared spectra showed new characteristic absorption peaks, indicating that the coconut water had undergone qualitative changes. It is recommended that bottled coconut water from freshly cut coconuts should be consumed on the same day.

Six mango varieties (Guiqi Mang, Tainong Mang, Guifei Mang, Jinhuang Mang, Ivory Mang, and Jade Mang) mainly planted in Baise were selected as the research objects, and 22 quality indicators (including appearance quality, internal quality.) were analyzed. The results indicated that the coefficient of variation for indexes such as single fruit weight and fruit shape index exceeded 10% among different varieties in appearance quality. For intrinsic quality, Guiqi mango performed optimally in sweetness-related indexes (TSS, total sugar, soluble sugar) and flavor coordination (solid-acid ratio, sugar-acid ratio), with the highest Vc content reaching 36.6 mg/100 g, while Tainong mango had the lowest Vc content at 28.7 mg/100 g. Yumang mango had the highest contents of phenolic substances (4.33 mg/100 g) and flavonoids (1.12 mg/100 g). Guifei mango and Yumang mango had relatively high protein contents, both at 1.0 g/100 g. Further analysis indicated that there existed both relative independence and close correlation among multiple quality index variables of mango. The 5 principal components extracted by principal component analysis accounted for 100% of the information of the above indexes, and the comprehensive quality ranking was as follows: Yumang mango>Guiqi mango>Tainong mango>Xiangya mango>Guifei mango>Jinhuang mango. Systematic clustering classified the 22 quality indexes into 3 categories: bioactive components (e.g., vitamins, flavonoids), fruit flavor characteristics (e.g., sugar-acid related indexes), and mineral elements (e.g., potassium, calcium). The results revealed the characteristic differences in fruit quality among the main mango varieties in Baise, and suggested that principal component analysis and systematic clustering analysis could be applied to simplify the evaluation of mango fruit quality.

Banana anthracnose, caused by Colletotrichum musae, is a major postharvest disease that threatens fruit quality and banana industry sustainability. Phospholipase (PL) plays dual roles in plant disease resistance and pathogen metabolism, acting as a key enzyme in defense responses and as a virulence factor for pathogenic fungi.. Previous studies have shown that PL inhibitors can help maintaining membrane stability under stress conditions. In this study, the inhibitory effects of three PL inhibitors, i.e. quinacrine dihydrochloride (QU), neomycin sulfate (NE), and n-hexanol (Hex), on C. musae were evaluated through in vitro antifungal assays. Results showed that all three inhibitors significantly suppressed mycelial growth and spore production of C. musae. The half-maximal inhibitory concentrations (IC₅₀) for mycelial growth were 1.00 mmol/L (QU), 5.00 mmol/L (NE), and 8.80 mmol/L (Hex). Enzymatic activity assays revealed that QU significantly inhibited both PLA activity in C. musae and banana peel tissues, NE primarily suppressed PLC activity in banana peel, whereas Hex markedly reduced PLD activity in C. musae. Moreover, the appropriate concentrations of the inhibitors (2.00 mmol/L QU, 3.00 mmol/L NE, and 13.20 mmol/L Hex) effectively controlled the development of banana anthracnose. The findings suggested that QU, NE, and Hex suppressed banana anthracnose through distinct mechanisms involving interference with host-pathogen interactions. This study would provide a theoretical basis for the green control of postharvest banana diseases via the targeted regulation of phospholipase activity.

The study was aimed to clarify the effects of different bag types on fruit quality and postharvest storage of Dongshizao pomelo, and screen suitable bag types to provide reference for production and application. In this study, 23-year-old Dongshizao pomelo trees were used as the experimental material, fruit without bagging was used as the control group, fruit bagging was carried out with 8 types of bags, including 60-mesh nylon mesh bag, 80-mesh nylon mesh bag, unilateral polyethylene-paper bag, white nonwoven bag, green-single-layer bag, white-single-layer bag, single-layer bag with yellow outside and black inside, double-layer bag with yellow outside and black inside. Fruit quality difference between harvest and post-harvest storage was compared, and comprehensive evaluation was carried out by the subordinative function method. The results showed that the white-single-layer bag significantly increased the single fruit weight by 47.86%, double-layer bag with yellow outside and black inside significantly decreased the pericarp thickness by 28.19%, and the total soluble solids (TSS) content of fruits with single-layer bag with yellow outside and black inside was significantly decreased. The titratable acid (TA) content of fruits with unilateral polyethylene-paper bag, single-layer bag with yellow outside and black inside, double-layer bag with yellow outside and black inside were decreased. While the single-layer bag with yellow outside and black inside, double-layer bag with yellow outside and black inside were significantly improved the TSS/TA rate by 19.71% and 34.40%, respectively. At harvest, the comprehensive evaluation of fruit quality revealed that fruits bagged with the double-layer bag with yellow exterior and black interior achieved the highest score (0.56), followed by those with the single-layer bag of the same design (0.55), both outperforming the unbagged control (0.50) and white single-layer bag (0.49). During postharvest storage, the fruit weight loss rate generally increased with storage duration, except for one transparent paper bag treatment, and peaked on the 45th day of storage. Throughout the storage period, significant differences were observed in various fruit quality indices, including edible rate, juice yield, soluble sugar, soluble protein, TSS, and TA content, with fluctuations influenced by bag type. Regardless of treatment, the inherent quality indices of the fruit pulp exhibited significant variability rather than a simple upward or downward trend. The bagged fruits also displayed a distinct ‘returned acidity’ phenomenon, with the timing and intensity of this phenomenon influenced by the type of bag used. The comprehensive evaluation of postharvest storage quality showed that the average comprehensive score of fruits bagged with the white single-layer bag gradually increased with extended storage time, reaching the highest average score (0.65) among all treatments, with the smallest coefficient of variation (5.14%). In conclusion, while fruits bagged with the single-layer and double-layer bags with yellow exterior and black interior demonstrated superior comprehensive quality at harvest, they exhibited greater quality fluctuations and poorer storage stability. Conversely, although the initial harvest quality of fruits bagged with the white single-layer bag was slightly inferior to the control, this treatment exhibited the smallest variation range in storage quality, coupled with the highest overall storage quality and stability. Therefore, the white single-layer bag is recommended as the primary bagging option for the production and cultivation of Dongshizao pomelo, offering a balanced approach to optimizing both fruit quality and postharvest storage performance.

Ammonia preservation and acid solidification are key steps in natural rubber (NR) processing, but there is still a lack of systematic research on the influence on the structure and properties of NR. In this paper, the same batch of fresh latex was treated with 0%, 0.05%, 0.20% ammonia and two solidification methods (acid solidification, biological solidification) to prepare samples. The effects of ammonia preservation and acid solidification on the structure and properties of NR were comprehensively evaluated from the aspects of molecular structure, composition, intrinsic properties, and the mechanical performance of both unfilled and carbon-black-filled vulcanizates. It was found that ammonia preservation led to a decrease in weight-average molecular weigh, the initial plastic value and Mooney viscosity of the acid-solidified samples, whereas the properties remained largely unaffected in biologically solidified counterparts. The addition of ammonia exerted minimal influence on the mechanical properties of unfilled vulcanizates, but significant effects emerged in carbon-black-filled systems. Acid-solidified samples demonstrated higher fatigue temperature rise, while biologically solidified samples showed decreased tensile stress and tear strength. The solidification mode profoundly impacted the molecular structure, chemical composition, intrinsic properties, and mechanical performance of NR. Compared to biological solidification, acid-solidified rubber exhibits higher nitrogen, free fatty acid content and weight-average molecular weight. Furthermore, acid-solidified samples displayed lower initial plasticity and Mooney viscosity. The solidification method significantly affected the properties of both unfilled and carbon-black-filled vulcanizates. Compared to biological solidification, acid-solidified samples exhibited slower cure rates and higher fatigue temperature rise. The results showed that ammonia preservation of fresh latex and subsequent solidification with acid could affect the important components and intrinsic properties of NR, and had a significant impact on the dynamic properties such as fatigue temperature rise and permanent deformation, especially in carbon-black-filled vulcanizates. However, by comparing with the imported RSS, the preservation of fresh latex with ammonia and the subsequent solidification with acid were not the only reasons causing the performance of domestic NR to be worse than that of imported NR and differences in processing maybe the other causes. This work not only reveals the reason of the performance difference between domestic and imported NR products, but also would provide technical support for optimizing the production management of special rubber park.

The maize leaf area index (LAI) is a key parameter for reflecting growth and yield of maize, and the pollination stage being crucial for determining ear kernel number and yield. This study aimed to identify an effective inversion method to accurately estimate the LAI of Nanfan maize at pollination stage. Nanfan maize at pollination stage was used as the study subject. Canopy reflectance data were acquired using a ULTRIS X20 PLUS hyperspectral imager mounted on a Jingwei M300RTK quadrotor UAV platform. Based on correlation analysis, 28 LAI-sensitive vegetation indices were selected. Two traditional empirical models, univariate linear regression (ULR) and multiple stepwise regression (MSR), and four machine learning models, partial least squares regression (PLSR), random forest regression (RFR), support vector regression (SVR) and back propagation neural network (BPNN) were employed to construct LAI inversion models. The prediction accuracy of different vegetation indices and regression algorithms was compared, and the optimal inversion model was selected for accurately predicting the LAI status of Nanfan maize at pollination stage. Most vegetation indices exhibited highly significant correlations with LAI (P<0.01). Compared to univariate regression, multivariate regression models provided higher prediction accuracy. Among them, RFR, MSR and PLSR models achieved the highest R² values, with coefficients of determination (R²) of 0.96, 0.85 and 0.80 and corresponding root mean square errors (RMSE) of 0.18, 0.35 and 0.41, respectively. By analyzing the correlation and sensitivity between hyperspectral data and maize LAI, and employing vegetation indices calculated based on hyperspectral information combined with regression algorithms, this study successfully developed a reliable LAI inversion model, and established a spatial distribution of Nanfan maize LAI at pollination stage based on the RFR model with the best inversion effect. The model would provide both theoretical support and technical guidance for LAI estimation and field monitoring of Nanfan maize growth and development.

The present study investigated the ameliorative effects of 5-aminolevulinic acid (5-ALA) on muskmelon seedlings subjected to saline-alkali stress. Using the melon variety Zhongbao No.1 as the test material, under pot cultivation conditions, the study investigated the effects of root application of five different concentrations (25, 50, 100, 150, and 200 mg/L) of 5-ALA on the growth changes, photosynthetic pigments, reactive oxygen species (ROS) accumulation, osmotic adjustment, and antioxidant system of melon seedlings under 150 mg/L mixed salt-alkali stress. The results showed that under saline-alkali stress, exogenous 5-ALA at appropriate concentrations (100, 150 mg/L) significantly increased plant height, stem diameter, leaf length, leaf width, and leaf area of muskmelon seedlings. It also increased the contents of photosynthetic pigments and soluble sugars, proline content was reduced but still remained higher than that of CK, and significantly reducing both MDA content and O^2- generation rate. Furthermore, the activity of antioxidant enzymes, specifically SOD, CAT, APX, and GR, along with GSH content, exhibited elevation. Although POD activity showed a decrease, it maintained significantly higher levels compared to the control treatment (CK). In addition, TOPSIS comprehensive evaluation analysis was conducted on different exogenous 5-ALA treatments based on all the above measurement indicators, and the results showed that SA₁₅₀ treatment ranked first. Therefore, exogenous 5-ALA at a concentration of 150 mg/L exhibits the optimal effect in alleviating saline-alkali stress in muskmelon seedlings, which would provide a theoretical foundation for the cultivation of crops under saline-alkali stress conditions.

A field split plot experiment of pineapple was carried out from 2023 to 2024 to explore the effects of nitrogen fertilizer postponing and magnesium fertilizer coupling on the growth and development, yield and quality of pineapple and to provide practical reference for scientific fertilization management of pineapple. The main area was magnesium application rate, namely MgO 0 kg/hm² (M₀), MgO 37.5 kg/hm² (M₁) and MgO 75 kg/hm² (M₂). The sub-area was conventional nitrogen application treatment (N₁) and nitrogen fertilizer postponing treatment (30% of nitrogen fertilizer in slow growth period and flowering period was postponed to rapid growth period and fruit enlargement period, respectively) (N₂). The leaf number, leaf area index, chlorophyll content, dry matter accumulation, yield and quality indexes of pineapple were measured during the key growth period of pineapple. The results showed that compared with N₁, N₂ could significantly increase the contents of chlorophyll a and chlorophyll b in pineapple leaves at mature stage, and increase the number of leaves and leaf area index of pineapple at red stage. Compared with N₁, the dry matter quality and yield at maturity stage increased by 9.40% and 7.65%, respectively, and the vitamin C content and soluble sugar content of fruit were also significantly higher than those of N₁ (P<0.05), while the difference in yield was not significant. Similarly, compared with M₀ and M₂ treatments, M₁ treatment could significantly increase the contents of chlorophyll a, chlorophyll b and carotenoids in leaves, and the leaf number and leaf area index of pineapple at the red stage of flowering increased significantly, thereby improving the dry matter quality and yield at the mature stage, and the difference was significant (P<0.05). The fruit dry matter distribution rate, soluble sugar content, soluble protein content, vitamin C content and sugar-acid ratio under M₁ treatment were significantly higher than those under M₀ and M₁ treatments (P<0.05). Interaction effect analysis revealed that N₂M₁ treatment could increase the content of chlorophyll a, chlorophyll b and carotenoid in pineapple compared with other treatments, and then the number of leaves, leaf area index and dry matter quality increased significantly. Yield increased significantly by 19.43%, 17.39%, 10.07% and 24.96% compared with those of N₂M₀ (P<0.05), N₁M₂, N₁M₁ and N₁M₀, respectively, but not significantly different from that of N₂M₂. The fruit shape index, vitamin C, soluble sugar, soluble protein content and sugar-acid ratio of pineapple fruit treated with N₂M₁ were higher than those of other treatments, and there was a significant difference between N₂M₁ and N₁M₀ (P<0.05). Correlation analysis showed that pineapple yield was significantly positively correlated with leaf number, leaf area index, dry matter accumulation, chlorophyll b content, vitamin C, soluble sugar and soluble protein. There was a significant negative correlation with titratable acid content. N₂M₁ treatment can significantly increase the number of leaves, leaf area index and photosynthetic pigment content of pineapple plants, increase fruit dry matter distribution, thereby increasing pineapple yield and effectively improving fruit quality. Therefore, N₂M₁ could be recommended as the best model for fertilization management of pineapple in tropical regions.