RESUMO
Plants synthesise a vast array of volatile organic compounds (VOCs), which serve as chemical defence and communication agents in their interactions with insect herbivores. Although nitrogen (N) is a critical resource in the production of plant metabolites, its regulatory effects on defensive VOCs remain largely unknown. Here, we investigated the effect of N content in tomato (Solanum lycopersicum) on the tobacco cutworm (Spodoptera litura), a notorious agricultural pest, using biochemical and molecular experiments in combination with insect behavioural and performance analyses. We observed that on tomato leaves with different N contents, S. litura showed distinct feeding preference and growth and developmental performance. Particularly, metabolomics profiling revealed that limited N availability conferred resistance upon tomato plants to S. litura is likely associated with the biosynthesis and emission of the volatile metabolite α-humulene as a repellent. Moreover, exogenous application of α-humulene on tomato leaves elicited a significant repellent response against herbivores. Thus, our findings unravel the key factors involved in N-mediated plant defence against insect herbivores and pave the way for innovation of N management to improve the plant defence responses to facilitate pest control strategies within agroecosystems.
RESUMO
OBJECTIVE: To investigate the constitutive characteristics and the change trend of gynecologic malignant tumors in hospitalized patients in Guangxi Zhuang Autonomous Region over the recent 20 years. METHODS: Clinical data of 8009 in-patients who suffered from gynecologic malignant tumors in 23 hospitals from 1985 to 2004 in Guangxi Zhuang Autonomous Region were analyzed, with respect to the tumor types and change trend. RESULTS: (1) The leading 4 types of malignant tumors were cervical cancers, ovarian cancers, endometrial cancers, and malignant trophoblastic tumors according to the constitutive ratios of the tumors. The constitutive ratio of cervical cancer patients rose year by year, from 17.48% during the 1985-1989 period to 49.25% during the 2000-2004 period (P < 0.01). While the constitutive ratio of malignant trophoblastic tumors dropped year by year. The changes of ovarian cancer, endometrial cancer, vulvar and vaginal carcinomas, and sarcoma of the uterus were not obvious (P > 0.05). (2) The occurring age of cervical cancers became younger obviously, from > or = 60 years old dropped to < 40 years old. (3) Cervical cancers were found mainly in urban residents in the former 10 years, the constitutive ratio being 67.1%; while in the latter 10 years it gradually shifted to rural residents, accounting for 52.6% of the total gynecological tumors. (4) Patients were usually at stages II, III, IV when they visited a doctor for their diseases. Especially for ovarian cancer, malignant trophoblastic tumors, sarcoma of the uterus, these patients were in the intermediate or advanced stage when they were diagnosed, mainly because of lack of obvious symptoms. The constitutive ratio of these advanced patients was over 60%. CONCLUSIONS: We should strengthen the screening program of cervical cancer, and pay more attention to prevention and control of other gynecological reproductive organ tumors at the same time. On the other hand, we should explore better tumor markers, new methods of diagnosis and treatment to improve early diagnosis and treatment of gynecologic malignant tumors.