White-fruited pepper is a highly distinctive type of pepper in Zhejiang province. In order to determine the optimal nitrogen level for this variety, a facility cultivation experiment was conducted to analyze the effects of five different nitrogen treatments: 0 kg/hm², T₀; 150 kg/hm², T₁; 195 kg/hm², T₂; 240 kg/hm², T₃; 285 kg/hm², T₄, on the growth, development, quality and accumulation of nitrogen elements in white pepper plants. The results showed that the main stem height, plant height, canopy width, stem diameter, stem and leaf biomass and yield of peppers increased with the application of nitrogen. Notably, fruit width, single fruit weight and yield reached the maximum under the T₄ treatment, with increased of 36.27%, 76.30% and 32.16% respectively compared to the control, followed by T₃, while the T₃ treatment produced the longest fruits. Furthermore, the photosynthetic capacity of the pepper leaves improved with higher nitrogen application, with T₃ and T₄ treatments showing significantly better performance than the others. The quality of peppers was also influenced by nitrogen application. Nitrogen application also affected the quality of the pepper. The content of vitamin C and dihydrocapsaicin decreased with the increasing nitrogen levels, while the levels of capsaicin, total capsaicin and amino acids showed a trend of first increasing and then decreasing. Different nitrogen levels had a minor impact on nitrogen absorption in the roots, stems and fruits of peppers, but significantly affected nitrogen absorption in the leaves, with the T₂ treatment achieving the highest leaf nitrogen content. Through principal component analysis of the 10 indicators related to yield and quality, the optimal nitrogen application for white-fruited peppers is T₃ (240 kg/hm²).

The study on the ecological suitability regionalization for jackfruit (Artocarpus heterophyllus Lam.) is of great significance for guiding its cultivation layout and digging its development potential, via utilization of environmental resources efficiently in tropical and subtropical regions. Based on the analytic hierarchy process (AHP) and GIS, this study constructed a suitability analysis model for jackfruit cultivation using four evaluation factors: temperature, precipitation, sunshine hours and soil index. The results of the regionalization are then validated in conjunction with previous research findings and the actual distribution of jackfruit, while further explore the spatial potential for jackfruit cultivation by integrating land use spatial data. The results indicate that the zones able to plant are primarily distributed in tropical and subtropical monsoon climate regions. The suitable zones for planting are mainly found in Hainan, southern Guangxi, southern Guangdong, parts of southern Yunnan and southern Fujian, where there is sufficient heat throughout the year, favorable wintering conditions, and a good combination of light, heat and water. Total plantable area for jackfruit in China is approximately 47.85×10⁴km², of which 22.71×10⁴km² is suitable for cultivating, comprising 8.89×10⁴km² of arable land and 182.05 km² of unused land. In comparison to previous research findings, this study expanded the amount of potentially viable arable land for jackfruit cultivation by about 58 times the existing cultivating area. Considering comprehensive land use, ecological environment, and policy support, jackfruit has a high potential for production in suitable and relatively suitable arable and unused land in China. Priority should be given to developing suitable planting areas in the southern regions of Guangxi and Yunnan. The study findings could provide scientific and analytic references for optimizing the regional layout and development planning of jackfruit cultivation in China.

Citrus medica is an older cultivated varieties of the genus Citrus and the parent or ancestor of Citrus fruits with significant commercial value. Due to its nutritional and medicinal values, C. medica occupies an important position in the citrus industry. The southwestern part of China is an important center for the origin and diversity of C. medica, and its cultivation has reached a certain scale. Citrus Huanglongbing (HLB) has been spreading for hundreds of years in the major citrus-producing areas in China. C. medica infected with HLB and healthy C. medica were used as the materials. Firstly, the symptoms of the leaves and fruits of C. medica infected with HLB were observed. Secondly, the distribution pattern of HLB in different tissue parts of C. medica was explored. Meanwhile, the tissue anatomical structures and multiple physiological indicators of C. medica infected with HLB and healthy C. medica were analyzed and measured through comparison. Through comparative observation, it was found that the leaves of C. medica infected with HLB showed typical symptoms such as yellowing, mottling and mosaic, and some branches presented symptoms of witches broom and abnormal flowering, but no “red nose fruit” was observed. The distribution of HLB in different parts of the same C. medica was uneven, with the highest content in the fruit pith, followed by the midrib of the old leaves, and HLB was not detected in the fibrous roots. In C. medica infected with HLB, the cells in the phloem, xylem, parenchyma and root were arranged irregularly, the phloem tissue was deformed and collapsed, and the thickness of the phloem of the taproot was significantly decreased compared with that of the healthy C. medica at the same period (P<0.05). No obvious starch grain accumulation was observed in each tissue section of C. medica infected with HLB, but when the starch content was measured, it was found that the starch contents in the old leaves, new leaves, taproot, fibrous roots and fruit pith of C. medica infected with HLB were all higher than those of the corresponding healthy tissues. The hydrogen peroxide content in each tissue of the diseased C. medica increased significantly (P<0.5), especially significantly accumulated in the young tissues (new leaves, fibrous roots) infected with HLB. Compared with healthy C. medica, the callose deposition phenomenon in the tissues of C. medica infected with HLB, especially in the main root and the midrib of the old leaves, was more obvious. The research results of this study could provide a theoretical basis for the relevant studies on exploring the characteristics of damage caused by HLB and the defense mechanism of citrus against HLB in the future.

Based on the data of rice growth period in Dongfang and Ledong, main producers for rice seed reproduction in Hainan, and the meteorological data from 1971 to 2020, the Penman-Monteith formula and crop coefficient method and the method recommended by the Soil Conservation Service of the United States Department of Agriculture were used to obtain the water requirement (ET_c), effective precipitation (P_e) and water deficit (D_w) of rice seed reproduction in field period and early, middle and late stage of field period. The change characteristics of water supply and demand of rice seed reproduction in the two regions were then analyzed. The 50-year average value of ET_c in field period of rice seed reproduction in Dongfang and Ledong was 400.2 mm and 322.3 mm, respectively, the mean value of P_e was 45.7 mm and 84.3 mm, respectively, and the mean value of D_w was 354.5 mm and 238.0 mm, respectively. The ET_c and D_w in field period of rice seed reproduction were mainly distributed in the middle and early stages, accounting for 72.4% to 85.2% of ET_c and D_w during the field period. The P_e in field period of rice seed reproduction was mainly distributed in the late and middle stages, accounting for 78.2% and 85.6% of P_e during the field period, respectively. In the past 50 years, the ET_c and D_w of rice seed reproduction in field period and all growth stages of field period in Dongfang showed an increasing trend (the increase in field period was significant), while the P_e showed a decreasing trend. The variation trend of ET_c, P_e and D_w of rice seed reproduction with time in Ledong was roughly opposite to that in Dongfang. In the past 50 years, the water shortage situation of rice seed reproduction in Dongfang was significantly worsening, while the water shortage situation in Ledong was easing to some extent but remained severe. Effective measures should be taken to mitigate the impact of climate change on the rice seed reproduction. In the past 50 years, the main reasons for the increase of ET_c and D_w during most growth stages of rice seed reproduction in Dongfang were the insignificant increase in high temperature and extremely significant increase in low temperature, or the insignificant increase in high temperature and sunshine hours. The main reasons for the decrease of ET_c and D_w during most growth stages of rice seed reproduction in Ledong were the insignificant decrease in sunshine hours, extremely significant decrease in average wind speed, or insignificant decrease in sunshine hours and insignificant increase in precipitation. The results of this study provide strong support for rational water use and scientific irrigation scheme for rice seed reproduction in Hainan province under the background of climate change.

Helopeltis theivora Waterhouse belongs to the genus Helopeltis of the family Miridae of the order Hemiptera, and is one of the most important sap-sucking pests in the tropical tea plantations in Hainan, China. The nymphs and adults of H. theivora mainly damage by piercing and sucking in the young tissues of tea shoots, which causes the black brown spots that necrosis on the leaf and results in the reduction of tea yield and quality. The research on the H. theivora in Hainan tea region is still rare. In this paper, we first investigated the external morphological characteristics of H. theivora, then, the growth and development characteristics such as egg hatching, nymph molting, and adult emergence, as well as the behavioral characteristics including feeding, mating and oviposition were recorded and analyzed, respectively. The results showed that the egg of H. theivora was in a sausage shape, with two respiratory processes on the egg operculum at different length. The color of the freshly laid egg was white. It was then gradually transformed to the orange and ultimately exhibited the orange-red as it approached incubation. The nymphal stage was divided into 5 instars, the color of the freshly hatched nymph was orange-red, and then gradually turned to pale green and green. The adult H. theivora possessed a small head, an elongated beak, and two black compound eyes. The antennae presented filamentous, and the length was twice more than the body. The color of adult H. theivora was brown or yellowish brown. The duration of incubation of H. theivora was (53.25±9.00)min. The hatchability was very low while the rate of egg- hatching was only 69.9% under the laboratory conditions. The moulting of nymphs and the emergence of adults happened mainly on the back of leaves, hanging upside down, and the duration was (6.20±0.97)min and (8.40±1.33)min, respectively. Particularly, as approached to the molting and eclosion, the feeding frequency became significantly less and the activity became weaker. The H. theivora preferred to sucking the saps of the young leaves and stems of tea shoots, and the feeding time was mainly concentrated in the evening. The mating behavior of adults H. theivora mainly happened between 9: 00 and 10: 00 and between 17: 00 and 18: 00, and the duration of each mating was (117.75±18.70) min. In addition, when a female decided to refuse a male’s request for courtship, it generally rolled her abdomen inwards. The stage of the fertilized egg of H. theivora was short. During the oviposition, the female arched itsr abdomen, its head was downward, and the whole body was in a curvedly arched state. The oviposition site was mainly in the epidermis of the tender stems, while a small part of eggs was laid in the petiole and leaf vein. The egg stage was 6-8 days. The results of this study would provide a theoretical basis for the further study on the morphological identification and behavioral ecology of H. theivora in Hainan tea region.

Lodging was one of the important limiting factors for high yield, high sugar content and mechanized harvesting of sugarcane, and it was also an urgent problem to be solved in sugarcane mechanized breeding. In this study, 24 reciprocal hybrids of 57NG208 and Nanjian chewing cane and PT43-52 (CK) were used as research materials. The plant height, basal stem diameter, middle stem diameter, brix, center of gravity height, single stem weight, the lodging resistance index, basal and middle stem diameter ratio and stem breaking force were measured. The correlation analysis, principal component analysis, membership function method and cluster analysis were used to comprehensively evaluate them. The results showed that the coefficient of variation of 9 indexes such as lodging resistance index and agronomic traits of 25 materials was between 11.57% and 30.80%, and the traits were obviously separated and the variation was abundant. The correlation analysis showed that the lodging resistance index was significantly positively correlated with brix, basal stem diameter, basal and middle stem diameter ratio, center of gravity height, single stem weight and stem breaking force, and negatively correlated with plant height and middle stem diameter. The results of principal component analysis showed that the cumulative contribution rate of the first three principal components was 75.7717%, which represented most of the information of lodging resistance of the tested materials. Cluster analysis showed that 25 materials could be clustered into three categories, and the results were consistent with the results of membership function evaluation. Among them, 13 materials in the first category had excellent lodging resistance and high comprehensive evaluation scores, especially Yunrui 12-9-45, Yunrui 12-9-5, Yunrui 12-38-32, PT43-52 and Yunrui 12-38-46. The lodging resistance index of the remaining germplasms was 3.00 except Yunrui 12-38-46, and the comprehensive evaluation E value was in the top 5, which should be used in the future improvement of lodging resistance.

In order to select a new tobacco variety with excellent industrial and agricultural characteristics was selected, the tobacco variety Y87 was used as the control to compare and analyze the agronomic traits, ultrastructure, metabolites and post baking tobacco quality evaluation of four newly introduced tobacco varieties Y121, Y116, Y301 and Y119. The results showed that Y121 had relatively good field growth, complete chloroplast structure, and a large volume and quantity of osmium loving particles on the chloroplast membrane. Through metabolic pathway enrichment analysis, it was found that Y121 contained more organic acids such as succinic acid and phenylacetic acid, as well as fewer nicotine such as nicotine reducing and new tobacco alkaloids, which are beneficial for improving the aroma quality and safety of tobacco leaves. In addition, compared to other newly introduced varieties, the Y121 had better appearance quality, more coordinated chemical composition, higher sensory quality score, and is closer to Y87. The results would provide reliable technical support for the upgrading of varieties, which is conducive to the sustained and stable development of high-quality raw material production.

In order to explore the effect of DNA methylation on drought hardening of different ploidy watermelon, mannitol was used to mimic drought stress in suspension cultured cells of different ploidy watermelon. The cell growth and resistance related physiological indexes were measured after stress, recovery and re-stress treatments. Meanwhile, the DNA methyltransferase inhibitor 5-azacytidine (5-AzaC) was used to explore whether methylation is involved in resistance regulation. The results showed that 5-AzaC could retard the growth, inhibit the extracellular alkalization, increase the content of malondialdehyde, bring down the content proline and the activity of protective enzymes such as SOD in all types of cells. Moreover, it caused the membrane permeability raising in diploid and triploid cells. Above results suggest that 5-AzaC can aggravate the osmotic stress injury and reverse the effects of drought hardening partially. Principal component analysis revealed that malondialdehyde content, proline content, PAL, CAT and APX activity could be used as the main evaluation indexes for evaluation the effect of drought hardening. This study would provide clues for mining the physiological indexes for evaluate the effects of stress hardening and the mechanism of DNA methylation involved in watermelon resistance regulation.

Guangxi is the leading sugarcane production area in China. over 85% of the sugarcane is planted on non-irrigated dry land, and varying degrees of drought damage occur every year. Drought is the main limiting factor for sugarcane production in China. Tillering is one of the important traits affecting the yield of sugarcane. It is of great significance to study the effect of drought stress on the development of tillering buds at tillering stage. Guire 2 is a new sugarcane variety bred by our team with good drought resistance and strong tillering ability. In order to investigate the effects of drought stress on physiological indicators of sugarcane tillering seedlings and leaves at tillering stage, Guire 2 was used to conduct drought stress experiments at the early stage of sugarcane tillering. The experiment was set up with control (19%-25% soil absolute water content) and drought stress treatment by stopping irrigation. Samples were taken from the control group and treatment group at early drought stress (14%-15% soil absolute water content), middle drought stress (10%-11% soil absolute water content), late drought stress (6%-7% soil absolute water content) stages. The changes of antioxidant enzyme activity, MDA, osmoregulatory substances and endogenous hormone contents were measured by subordination function method. The correlation of the physiological indicators in sugarcane tiller shoots and leaves was analyzed, and the drought resistance of tiller shoots and leaves was evaluated. The results showed that drought stress increased the activities of peroxidase (POD), and superoxidate dismutase (SOD), and contents of proline (Pro), soluble protein, starch, sucrose and abscisic acid (ABA), especially in tiller shoots, the treatment group and the control group reached a significant difference, while the malondialdehyde (MDA) content remained at a similar level in sugarcane tillering seedlings and leaves during drought stress. Compared with leaves, drought stress significantly increased the activity of SOD and the contents of Pro, soluble protein and sucrose in tiller shoots. Correlation analysis showed that most significant correlations between the physiological indicators in sugarcane tiller shoots and leaves under drought stress were positive, and sucrose content, starch content, Pro content, IAA content and SOD activity were more significantly or extremely significantly correlated with other indicators. According to the comprehensive drought resistance coefficient and the average of subordinate function values of each index, the drought resistance of tiller shoots was stronger than that of leaves in sugarcane.

Enhancing photosynthesis is the key to improving crop yield and quality. The interaction between agronomic traits, photosynthetic parameters, and variety yield and quality is not yet clear. In this study, 10 different mulberry varieties (Morus sp.) were taken as the research objects. Based on the morphological data such as leaf size, the number of leaves, the number of branches, etc., obtained through the statistics of our research group, the nutritional index data such as crude protein, and the measured photosynthetic parameters, we analyzed the correlations of specific parameters within each index through correlation analysis. And we utilized the structural equation model to analyze the influence mechanism and contribution potential of their agronomic traits, stomatal characteristics, and photosynthetic indexes on the yield and quality of mulberry leaves. There were significant differences in stomatal characteristics and photosynthetic indicators among different varieties, and Sha 2×Lun 109 exhibited good photosynthetic capacity and water use efficiency. There was a significant correlation between intercellular carbon dioxide concentration and leaf length, leaf width, and total calcium content. There was a strong positive correlation between stomatal length and width (r=0.833), and a positive correlation between crude protein content and leaf weight (r=0.660). The structural equation model indicated that the stomatal characteristics had a negative effect on leaf quality (R²=–0.75), while the intercellular carbon dioxide concentration had a negative effect on net photosynthetic rate (R²=-0.91). The intercellular carbon dioxide concentration and net photosynthetic rate directly affected leaf yield (R²=2.99 and 3.04, respectively), and leaf yield had a positive effect on leaf quality (R²=0.66). The research shows that mulberry varieties affect the net photosynthetic rate through stomatal characteristics and intercellular carbon dioxide concentration, which further affects the yield and quality of mulberry trees. Therefore, by regulating the parameters of mulberry stomata, the yield and quality of mulberry trees can be improved, which would provide a scientific basis for mulberry variety improvement and precision cultivation management, and has important practical significance.