Insect herbivores associated with an evergreen tree Goniorrhachis marginata Taub. (Leguminosae: Caesalpinioideae) in a tropical dry forest / Insetos herbívoros associados a uma árvore sempre verde Goniorrhachis marginata Taub. (Leguminosae: Caesalpinioideae) em uma floresta tropical seca

Goniorrhachis marginata Taub. (Leguminosae: Caesalpinioideae) is a tree species found in Brazilian tropical dry forests that retain their leaves during the dry season. That being, we addressed the following question: i) How do insect diversity (sap-sucking and chewing), leaf herbivory and defensive traits (tannin and leaf sclerophylly) vary on the evergreen tree species G. marginata between seasons? The abundance of sap-sucking insects was higher in the dry season than in the rainy season. However, we did not verify any difference in the species richness and abundance of chewing insects between seasons. Leaf herbivory was higher in the rainy season, whereas leaf sclerophylly was higher in the dry season. However, herbivory was not related to sclerophylly. Insect herbivores likely decrease their folivory activity during the dry season due to life history patterns or changes in behaviour, possibly entering diapause or inactivity during this period. Therefore, G. marginata acts as a likely keystone species, serving as a moist refuge for the insect fauna during the dry season in tropical dry forest, and the presence of this evergreen species is crucial to conservation strategies of this threatened ecosystem.

Goniorrhachis marginata Taub. (Leguminosae: Caesalpinioideae) é uma árvore encontrada em florestas tropicais secas do Brasil que mantém as suas folhas durante a estação seca. Baseado neste fato, nós levantamos a seguinte questão: i) como a diversidade de insetos herbívoros (sugadores e mastigadores), herbivoria foliar e características defensivas (taninos e esclerofilia foliar) variam em G. marginata entre as estações seca e chuvosa. A abundância de insetos sugadores foi maior na estação seca, entretanto, a riqueza e abundância de insetos mastigadores não diferiram entre as estações. A herbivoria foliar foi maior na estação chuvosa, enquanto a esclerofilia foliar foi maior na estação seca. Não foi observado efeito significativo da esclerofilia sobre os níveis de herbivoria foliar. Insetos herbívoros reduzem a sua atividade de consumo foliar durante a estação seca, fato este devido à sua história natural e/ou mudança comportamental, provavelmente, entrando em diapausa durante este período. Nossos resultados demonstram que G. marginata atua como refúgio para fauna de insetos durante a estação seca, e que a presença desta espécie merece relevante destaque em estratégias de conservação deste ameaçado ecossistema.

Elevated CO2 influences photosynthetic characteristics of Avena sativa L cultivars.

The impact of elevated CO2 concentration on the growth, photosynthesis and biomass production was investigated in three oat (Avena sativa L) cultivars viz. Kent, JHO-822 and JHO-851 by growing under three environmental conditions i.e. elevated CO2 at 600 ± 50 μ mol mol-1 (C600), OTC with ambient CO2 (COTC) and under open field condition (Ca). Plant height and leaf area increased in the elevated CO2 grown plants. JHO-822 attained maximum height under C600 followed by Kent and JHO-851. The specific leaf mass (SLM) and specific leaf area (SLA) were also influenced significantly when the plants were grown under C600. Kent showed highest SLM under C600 corresponding lower value of SLA. The accumulation of soluble protein in the oat leaves decreased under C600 except JHO-822 where marginal increase in soluble protein was recorded under C600. JHO-822 showed an increase in Chl orophyll a, b and total in C600 over Ca, whereas other two cultivars did not follow any specific trend in the pigment accumulation. Our results confirmed that the net phosynthetic rate (PN) increased by 37% in Kent followed by JHO 822 under elevated CO2 over the control. This strong association of PN with gs was evidenced by a positive significant correlation (r=0.885**). A clear stimulatory effect at elevated CO2 was detected in all the cultivars in term of green and dry matter production than at ambient CO2 and COTC. A large increase in PN in the present investigation was accompanied by relatively small decrease in gs, which limits the water loss through transpiration rate. The elevated CO2 induced changes in gs and reduction in transpiration.