Asymmetric plant-mediated cross-effects between a herbivorous insect and a phytopathogenic fungus

• 1 Cross‐effects between a herbivorous insect and a phytopathogenic fungus on their common host plant were examined. Specifically, we addressed the questions whether (i) infection of Chinese cabbage leaves by the fungus Alternaria brassicae affects the development and host selection behaviour of the leaf beetle Phaedon cochleariae and (ii) whether herbivory influences host suitability of Chinese cabbage for A. brassicae.
• 2 Feeding on fungus‐infected leaves prolonged larval development and reduced pupal weight of P. cochleariae. Adult beetles avoided feeding and egg deposition on fungus‐infected leaves. In contrast to these local effects, no systemic effect of phytopathogenic infection on the herbivore was detected.
• 3 Herbivory did not influence fungal growth neither locally nor systemically.
• 4 Thus, our results demonstrate an asymmetric relationship between herbivore and fungus. Whereas herbivory had no visible impact on fungal growth, fungal infection of the plant induced local resistance against P. cochleariae.

     

Salicylic acid inhibits jasmonic acid-induced resistance of Arabidopsis thaliana to Spodoptera exigua

The role of salicylic acid (SA) in plant responses to pathogens has been well documented, but its direct and indirect effects on plant responses to insects are not so well understood. We examined the effects of SA, alone and in combination with jasmonic acid (JA), on the performance of the generalist herbivore, Spodoptera exigua, in wild-type and mutant Arabidopsis thaliana genotypes that varied genetically in their ability to mount SA- and JA-mediated defence responses. In one experiment, growth of S. exigua larvae was highest on the Wassilewskija wild-type, intermediate on the Columbia wild-type and the JA-deficient fad mutant, and lowest on the nim1-1 and jar1-mutants, which are defective in the SA and JA pathways, respectively. Activity of guaiacol peroxidase, polyphenoloxidase, n-acetylglucosaminidase, and trypsin inhibitor varied by genotype but did not correlate with insect performance. SA treatment increased growth of S. exigua larvae by approximately 35% over all genotypes, but had no discernable effect on activities of the four defence proteins. In a second experiment, growth of S. exigua was highest across treatments on the cep1 mutant, a constitutive expressor of high SA levels and systemic acquired resistance, and lowest on the fad mutant, which is JA-deficient. JA treatment generally increased activity of all four defence proteins, increased total glucosinolate levels and reduced insect growth by approximately 25% over all genotypes. SA generally inhibited expression of JA-induced resistance to S. exigua when both hormones were applied simultaneously. Across genotypes and treatments, larval mass was negatively correlated with the activity of trypsin inhibitor and polyphenoloxidase and with total glucosinolate levels, and insect damage was negatively correlated with the activity of polyphenoloxidase. SA had little effect on the induction of defence protein activity by JA. However, SA attenuated the induction of glucosinolates by JA and therefore may explain better the interactive effects of SA and JA on insect performance. This study illustrates that direct and indirect cross-effects of SA on resistance to S. exigua can occur in A. thaliana. Effects of SA may be mediated through effects on plant defence chemistry or other aspects of the suitability of foliage for insect feeding and growth.     

下肢优势侧和非优势侧相同负重往返跑对青年学员平衡能力的影响

目的：本研究评定运动强度相同,不同运动量下肢优势侧和非优势侧相同负重往返跑对青年学员平衡能力产生的影响。方法：10名健康男性受试者平均年龄（20.80±2.04）岁,身高（173.99±2.87）cm。采用随机交互设计,10名受试者分别完成4次单侧负重往返跑：优势侧20 m×5、非优势侧20 m×5、优势侧20 m×10和非优势侧20 m×10,分别在运动后即刻和运动后20 min进行平衡能力测试,并记录R-R间期。结果：与安静状态相比,运动后,HR、EPOC和TRIMP值均显著增加（P<0.01）,优势侧和非优势20 m×10 EPOC和TRIMP值显著大于20 m×5（P<0.01）。与安静值相比,优势侧和非优势侧20 m×5和20 m×10运动后即刻,整体、前后和左右方向摆动均显著增加（P<0.05）,20 m×10优势侧和非优势侧左右方向摆动程度均显著高于20 m×5（P<0.05）,但优势侧和非优势侧之间不存在显著差异（P>0.05）,表现出对称性的变化;此外,恢复期20 min内均迅速回落到安静值（P>0.05）。结论：运动后即刻平衡能力受到干扰;运动量增加,左右方向损害程度增加;优势侧和非优势侧平衡能力的变化相似,可能存在交互效应。