Seed germination is a key link for plants to enter the vegetative growth stage. During the germination of rice (Oryza sativa L.) seeds, the aleurone layers synthesize and secrete a series of acid hydrolases (such as α-amylase, protease) to degrade the storage substances in the endosperm and provide nutrition for the growth of rice seedlings. The degradation of storage proteins is inseparable from the role of proteasome and protease in rice seeds. In order to explore the involvement of 26S proteasome, 20S proteasome and its subunit PBA1 in the regulation of GA on the storage proteins in the aleurone layers of germinated rice seeds, the rice hybrid Teyou 128 was used as the experimental material. The activity of 26S proteasome, 20S proteasome and PBA1, the transcription level of OsPBA1 and the change of total protein content were detected by enzyme-linked immunosorbent assay and real-time fluorescence quantitative PCR. GA significantly promoted the degradation of storage proteins in aleurone cells and accelerated the germination of rice seeds. When GA synthesis was blocked, the degradation process of storage protein in aleurone layer cells was delayed, thus delaying the germination of rice seeds. Under normal culture conditions, the peak values of 26S proteasome activity and 20S proteasome activity in the aleurone layers of rice seeds appeared at 6 d and 7 d, respectively, while the OsPBA1 expression level and PBA1 activity showed peaks at 5 d and 8 d. Further studies showed that GA could induce the activity of PBA1, 20S proteasome and 26S proteasome, thereby accelerating the process of seed germination. The 26S proteasome activity inhibitor MG132 inhibited the growth of germinated rice seeds, but increased the activity of 20S proteasome and PBA1. The above studies preliminarily revealed the role of 26S proteasome in GA regulating the degradation of storage proteins in rice aleurone layers and its effect on the germination of rice seeds.

Cassava (Manihot esculenta Crantz) is the third largest food crop in the tropics and is the food ration of nearly 600 million people in the world. Cassava is mainly cultivated in tropical regions, where often damaged by waterlogging in rainy season, which leads to serious decline in yield and quality. Therefore, it is important for selecting cassava germplasm resources with high waterlogging-resistance. In this study, a pot experiment was carried out, and plant height increment, relative chlorophyll content (SPAD), relative conductivity, superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) of 28 cassava germplasm resources were measured under waterlogging stress treatment after 6 days. Variance, correlation analysis, principal component analysis and subordinate function analysis were used to evaluate waterlogging resistance and screen the waterlogging tolerant germplasms at the seedlings stage. The waterlogging tolerance of 28 cassava germplasms had great difference and the response mechanism of different cassava germplasms to waterlogging stress showed huge difference among the 28 germplasm resources. There were significant positive correlation between plant height increment and relative chlorophyll content (P<0.01), and the correlation coefficient was 0.253. There were negative correlation coefficient between the relative chlorophyll content with relative conductivity of 0.266 (P<0.01). Principal component analysis using 6 indexes indicated that the 4 principal components accounted for 82.85% of accumulative contribution rates among the germplasms. The main factors were CAT, plant height increment, SOD, and relative chlorophyll content, respectively. According to subordinate function analysis, waterlogging tolerance of the germplasms from high to low was Qiongzhong 1, SC6068, SC201, ME191, M-F532, GR891, C222, GR3, F2000, Luoyong 80, 46-12, GR5, KU58, H660, SC5, F03P, M-GR911, CH20, M-F671, COL713, Boss 2, JG1301, GR911, E407, F274, SC8, M-SC5, Thailand. The results of this study would provide basic materials for the breeding of new varieties of cassava with high waterlogging-tolerance and for the future research of cassava waterlogging tolerance mechanism.

Spontaneous plants have strong growth adaptability, can self-multiply and form a good natural landscape, which are important materials for the construction of conservation-oriented landscape. The typical-sampling method was used to investigate the spontaneous plants in 16 city parks of Haikou, so as to comprehensively understand the diversity level of spontaneous plants and provide reference for the construction of conservation-oriented gardens. The results showed that 220 spontaneous plant species belonged to 59 families and 176 genera were recorded in this research. Among them, 154 plants were native plants (accounting for 70%) and 66 plants were exotic species (accounting for 30%), meanwhile, 48 plants were invasive alien species (accounting for 22.27%). Asteraceae, Poaceae and Fabaceae, the largest families, played a major role in the quadrats with 75 species from 64 genera, accounting for 36.36% and 34.09% of the total genera and species of Spontaneous plants. Perennial herbs and annual/biennial herbs were the main life forms, accounting for 51.36% (113 species) and 44.09% (97 species), respectively. Spontaneous plants have strong ecological adaptability and high potential for landscape application. In the future construction of urban landscape, the existing spontaneous plants in the parks should be reasonably planned and utilized, increasing the proportion of native plants and constructing the spontaneous plants landscape with regional characteristics according to different environments.

Low temperature is one of the main environmental factors affecting the growth, yield and distribution of sugarcane. It is of great significance to explore the physiological response characteristics of sugarcane under low temperature stress and screen strong cold-tolerant sugarcane parent materials for guiding sugarcane breeding and promoting the development of sugarcane industry. In this study, eight different sugarcane varieties and one sugarcane wild species (Erianthus fulvus 99-1 clone) were used as the experimental materials to study the physiological index response after low temperature stress treatment, and the cold tolerance of the nine materials was comprehensively evaluated by principal component analysis, fuzzy membership function method and cluster analysis. The contents of malondialdehyde (MDA), chlorophyll (Chl), soluble sugar (SS) and soluble protein (SP) in most materials were higher than those of CK after low temperature stress (3 ℃, 3 days). The content of proline (Pro) in all materials was higher than that of CK, while the activity of superoxide dismutase (SOD) was lower. The activities of peroxidase (POD) and catalase (CAT) in most materials were higher than those of CK. According to the comprehensive evaluation value (D) and cluster analysis, the nine materials were divided into three groups: strong cold resistance type (E. fulvus 99-1, Yacheng 89-9, ROC10), moderate cold resistance type (ROC20, Yuetang 93-159, Huangjiali, ROC16) and weak cold resistance type (Dianzhe 01-58, ROC22). The results indicate that different sugarcane varieties have different adaptability to low temperature. Strong cold-tolerant sugarcane varieties can quickly adjust themselves under adversity, reasonably increase the content of osmotic adjustment substances and the activity of antioxidant enzymes, further remove harmful substances such as reactive oxygen species (ROS) in the body, and balance cell metabolism process, so as to better adapt to low temperature environment. This study would lay a foundation for exploring the regulation mechanism of sugarcane response to low temperature stress and breeding new sugarcane varieties with strong cold tolerance.

Pepper mild mottle virus (PMMoV) is one of the most serious pathogens worldwide. Currently, five pathogenic types of PMMoV have been reported, including P₀, P₁, P_1,2, P_1,2,3 and P_1,2,3,4. The wide host range and strong pathogenicity of PMMoV seriously affect the yield and quality of pepper, and breeding for disease resistance is the most economical and effective means to control this virus. Our previous study determined that PMMoV infected with Danzhou pepper germplasm nursery in Hainan is the P_1,2 pathogenic type. In order to screen PMMoV-resistant pepper germplasm resources, 110 germplasms were tested for PMMoV resistance using the reported L³-linked molecular markers. 46 pepper germplasms containing molecular markers of resistance were inoculated with PMMoV P_1,2 pathogenic type by inoculation at seeding stage. Local symptoms were investigated 5 d after inoculation, and systemic symptoms were investigated 20 d after inoculation, and disease indices were calculated. The results showed that there were sig-nificant differences in disease resistance among different pepper germplasms, and the disease indexes of various germplasms ranged from 8.86-60.00. The germplasms showing high resistance (HR) to PMMoV P_1,2 pathogenic type were CF19-34m and 19FB6-1. The germplasms showing resistance (R) wasCCJ93-1. The germplasms showing medium-resistance (MR) included 17YB32, 17SCa28m, 15SM39-2, 14SM555×14SM1, 14SM567-2, 14SM526-1, 14SM565-1, 14SM502-1, 14SM519-1, 14SM504m, 14SM503m, 14SM519-3, 14SM518-2, 14SM519-2, CCJ52-1, etc. The presenting susceptible (S) germplasms were 14SM514m, CCJ22-1, CCJ113-2, CCJ135-1, CCJ157-1, L537-1m, L545, CCJ87-2 and CCJ133-1, and the obtained disease-resistant germplasms accounted for 80.43% of the total identified materials. The results of this study would lay the foundation for creating germplasm resources resistant to pepper mild mottle virus and breeding resistant varieties.

Tea quality is closely related to the growth and ecological environment of tea plant (Camellia sinensis). The difference between day and night temperature (DIF) affects the synthesis and accumulation of tea plant metabolites, which in turn affects the quality of tea. In this study, Fuyun No. 6 was selected as the research object, and four DIF treatments (0 ℃, 5 ℃, 10 ℃ and 15 ℃) were simulated to explore the effects of DIF on photosynthesis and volatile and non-volatilequality components of tea fresh leaves. The results showed that the net photosynthetic rate (P_n), stomata conductance (G_s) and transpiration rate (T_r) of tea plants increased significantly with the increase of DIF (P<0.05). Increasing DIF significantly increased the contents of chlorophyll a (Chl a), chlorophyll b (Chl b), chlorophyll (a+b) [Chl (a+b)] and carotenoids (Car), and reached the maximum when DIF was 10 ℃. In addition, the change of DIF had an effect on the volatile components and relative contents of main components in fresh tea leaves, and the relative contents of alcohols and aldehydes were the largest in the volatile components of fresh tea leaves. The increase of DIF could significantly enhance the relative contents of aldehydes, and the relative contents of volatile components and main aroma components in fresh tea leaves were different with the change of DIF. The content of hexanal increased with the increase of DIF, with the highest value of 39.94% at DIF=15 ℃, while the relative content of cis-3-hexenol decreased with DIF increasing. The change of DIF significantly affected the activities of β-glucosidase, β-primeverosidase and lipoxygenase. The activities of β-glucosidase and β-primeverosidase first increased and then decreased with the increase of DIF, and reached the maximum when the DIF was 5 ℃, while the activity of lipoxygenase was opposite. Furthermore, the contents of free amino acids and caffeine increased significantly with the increase of DIF, which were 2.44 and 2.55 times at DIF=15 ℃ than those at DIF=0 ℃, respectively. The total flavonoids content and ratio of tea polyphenols to amino acids decreased significantly with the increase of DIF (P<0.05), with the lowest value of 2.84% and 3.24 at DIF=15 ℃. The contents of free amino acids in fresh tea leaves were significantly positively correlated with P_n, while the ratio of tea polyphenols to amino acids showed significantly negatively correlated with P_n (P<0.01). This study indicated that the increase of DIF could significantly affect the volatile aroma substances of fresh tea leaves and improve the taste and quality of tea, which could provide a certain theoretical basis for tea plantation site selection and tea planting.

Eight main agronomic traits were statistically analyzed using cassava germplasm resources. The result showed that the data for the eight agronomic traits were normally distributed, with the coefficients of variation ranging from 7.2% to 46.9%. The coefficient of variation for starch yield was 46.9% and the coefficient of variation for the dry matter rate was 7.2%. Correlation analysis showed that there was a degree of significant positive correlation between the different traits, with a highly significant positive correlation between weight of fresh tuberous root per plant and stem diameter. Principal component analysis combined eight traits into three main components. The cumulative contribution rates in each year amounted to 92.55% and 93.67%, respectively. The first principal components were weight of fresh tuberous root per plant, fresh tuberous root yield, starch yield and dry tuberous root yield. The second principal components were starch content and dry matter. Cluster analysis suggested that the resources could be divided into four groups in each year at the Euclidean distance of 6.0. Group Ⅱ had excellent performances in weight of fresh tuberous root per plant, fresh tuberous root yield, starch yield and dry tuberous root yield, which could be preferred as parental materials for new cassava varieties selection and breeding of high yield and good quality.

The intercropping of Mallotus peltatus under the forest helps to break the bottleneck of land use. It is of great significance to apply green nanotechnology to improve the benefits of its compound planting. In order to clarify the regulatory role of nano-iron in the intercropping of M. peltatus under the coconut forest, the annual seedling of M. peltatus was taken as the research object to carry out the cultivation experiment. We investigated the comprehensive effects of five concentrations of nano-iron treatments (CK: 0 mg/L, T₁: 25 mg/L, T₂: 50 mg/L, T₃: 75 mg/L, T₄: 100 mg/L) on the leaf growth, photosynthetic and chemical characteristics of M. peltatus. After the first nano-iron treatment, the leaf length, width and dry weight of M. peltatus in T₃ treatment were significantly higher than those in CK, while the leaf number in each treatment was significantly more than that in CK. Compared with CK, the chlorophyll content of M. peltatus treated with four nano-iron concentrations increased significantly by 14.96% (T₁), 16.18% (T₂), 17.91% (T₃) and 20.58% (T₄). As the concentration of nano-iron increased, the leaf net photosynthetic rate, transpiration rate, stomatal conductance, efficiency of primary conversion of light energy of PSⅡ, actual photochemical efficiency of PS Ⅱ and electron transport rate of M. peltatus overall increased. After the second nano-iron treatment, leaf length, width, dry weight and number of M. peltatus treated with T₁, T₃ and T₄ were significantly higher than those of CK. Compared with CK, the chlorophyll content of M. peltatus in each treatment significantly increased by 10.28% (T₁), 7.53% (T₂), 11.13% (T₃) and 11.41% (T₄). With the increase of nano-iron concentration, the leaf net photosynthetic rate, transpiration rate and stomatal conductance of M. peltatus increased significantly, but decreased when the concentration reached T₃ treatment. The potential activity of PSⅡ and efficiency of primary conversion of light energy of PSⅡ of M. peltatus also decreased significantly in T₃ treatment. After two treatments, the contents of flavone, fat and ash of M. peltatus increased significantly in T₁ treatment compared with CK. The contents of fat and ash decreased with the increase of nano-iron concentration. To sum up, nano-iron has a positive regulatory effect on the growth of M. peltatus under the coconut forest, but high concentration will inhibit its photosynthesis and growth. We recommend that the appropriate concentration is 25-50 mg/L. This study could provide theoretical reference for the application of nano-iron in intercropping M. peltatus under the coconut forest.

Wampee [Clausena lansium (Lour.) Skeels] is a species of Rutaceae family and native to Southern China, which contains a large number of bioactive compounds that are beneficial to human health. However, because of the thin pericarp and soft pulp, wampee fruit is susceptible to the mechanical damage and the quality deterioration symptoms of fruit rot, pericarp browning and storage characteristic loss, and thus reducing the commercial value and edible value of harvested wampee fruit. Therefore, it is necessary to develop a safe and environmentally friendly postharvest storage technology for enhancing the storage behavior and quality, and prolonging storage time of harvested wampee fruit. Oxyresveratrol (OXY) is a naturally active product, with the efficacies of anti-browning, anti-oxidation, antibacterial, anti-inflammatory and antiviral. OXY has been studied more in the field of medicinal health care, but less in the field of food preservation. However, there are no reports on increasing the storage behavior and postharvest quality of wampee fruit by the usage of exogenous OXY. The study was aimed to study the effects of exogenous OXY treatment on the preservation of harvested wampee fruit. The fruit of wampee cv. Jixin was used as the experiment material, and the wampee fruit was treated by OXY solution with concentration of 0.2 g/L and distilled water (CK) for 30 min, separately. Then, the fruit was air-dried and packaged (50 fruits per bag), and stored at relative humidity 85% and temperature (25±1)℃ for 10 days. The changes of related indices of the storage behavior and postharvest quality in wampee fruit were observed and measured every two days. Compared to CK, OXY treatment could delay the increments of pericarp cell membrane permeability, browning degree and browning index, and maintain a higher commercially acceptable fruit rate but a lower weight loss percentage of harvested wampee fruit. Furthermore, OXY treatment might keep the higher values of L^* and hue angle, a higher total phenolics content, but the lower activities of phenolases such as peroxidase and polyphenol oxidase in pericarp of harvested wampee fruit. Moreover, OXY treatment could retain the higher contents of total soluble solids, vitamin C, titratable acidity, sucrose and total soluble sugar in pulp of harvested wampee fruit. Therefore, the treatment of exogenous OXY could effectively enhance the storage behavior, and retain the pericarp appearance quality and pulp nutritional quality, and thus prolong the storage time in harvested wampee fruit.

In August 2022, we found Phyllanthus urinaria with yellows and witches’-broom symptoms, respectively, in areca yellows disease garden in Wenchang city, Hainan province, which were phytoplasma infection. In order to clarify the taxonomic status of the phytoplasma strain in the yellows leaves and witches’-broom of P. urinaria. In this study, we cloned the 16S rDNA gene and ribosomal protein (rp) gene, and analyzed the gene sequence consistency, phylogenetic tree and virtual RFLP. The results showed that the 16S rDNA fragment 1246 bp and rp gene 1212 bp were cloned of P. urinaria yellows phytoplasma, the 16S rDNA fragment 1827 bp and rp gene 1240 bp were cloned of P. urinaria witches’-broom phytoplasma. The gene sequence consistency showed that the 16S rDNA gene sequence of the P. urinaria yellows phytoplasma and the P. urinaria witches’-broom phytoplasma was more than 98% consistent with the phytoplasma of 16SrⅠ group, and 100% consistent with the 16S rDNA sequence of areca yellows phytoplasma Hainan strain; the consistency of them in rp gene sequences was more than 99% to those of the rpⅠ group. The phylogenetic tree analysis showed that the 16S rDNA genes of P. urinaria yellows phytoplasma and P. urinaria witches’-broom phytoplasma were clustered in a large branch with those of aster yellows phytoplasma group (16SrⅠ), and clustered in the same small branch with those of areca yellows phytoplasma of 16SrⅠ-B subgroup, with the close genetic relationship; in the phylogenetic tree of rp gene, they were clustered in a large branch with the aster yellows phytoplasma group (rp Ⅰ), and clustered in the same small branch with those of aster yellows phytoplasma of rpⅠ-B subgroup, with the close genetic relationship. The virtual RFLP analysis showed that the RFLP map obtained by the 16S rDNA gene of the P. urinaria yellows phytoplasma and P. urinaria witches’-broom phytoplasma was the same as the reference map of the onion yellows phytoplasma of 16SrⅠ-B, and the similarity coefficient was 1.00. In summary, the P. urinaria yellows phytoplasma and the P. urinaria witches’-broom phytoplasma belong to 16SrⅠ-B subgroup in classification. The results of this study could provide a theoretical basis for the prevention and control of areca palm yellow disease by eradicating its intermediate host.