Striga seed-germination activity of root exudates and compounds present in stems of Striga host and nonhost (trap crop) plants is reduced due to root colonization by arbuscular mycorrhizal fungi.

Root colonization by arbuscular mycorrhizal (AM) fungi reduces stimulation of seed germination of the plant parasite Striga (Orobanchaceae). This reduction can affect not only host plants for Striga, resulting in a lower parasite incidence, but also false hosts or trap crops, which induce suicidal Striga seed germination, thereby diminishing their effectiveness. In order to better understand these AM-induced effects, we tested the influence of root colonization by different AM fungi on the seed-germination activity of root exudates of the Striga hermonthica nonhost plants cowpea and cotton on S. hermonthica. We also tested the effect of AM fungi on the seed-germination activity of the Striga gesnerioides host plant cowpea on S. gesnerioides. Moreover, we studied whether mycorrhization affects the transport of seed-germination activity to above-ground plant parts. Mycorrhization not only resulted in a lower seed germination of S. gesnerioides in the presence of root exudates of the S. gesnerioides host cowpea but also seed germination of S. hermonthica was also lower in the presence of root exudates of the S. hermonthica nonhosts cowpea and cotton. Downregulation of the Striga seed-germination activity occurs not only in root exudates upon root colonization by different AM fungi but also in the compounds produced by stems. The lowered seed-germination activity does not appear to depend on the presence of seed germination inhibitors in the root exudates of mycorrhizal plants. The implication for Striga control in the field is discusse

Mostly Heterosexual and Lesbian/Gay Young Adults:Differences in Mental Health and Substance Use and the Role of Minority Stress

Individuals mostly attracted to other-sex but also to same-sex partners are a distinct and common sexual orientation group with possibly increased levels of health problems. The current study examined whether mostly heterosexual individuals differed in mental health and substance use from lesbian/gay individuals and whether sexual minority risk and protective factors offer an explanation in a sample of 528 Dutch young adults (16 to 25 years old, M = 21.2 years). Mostly heterosexual participants reported higher levels of psychological distress, suicidality, drug use, and smoking than lesbian/gay participants and equal levels of binge drinking. They also reported higher levels of internalized negativity to same-sex attractions, less openness to family members and others, less community involvement, and lower numbers of lesbian/gay/bisexual friends. However, bootstrapped mediation analysis showed that the differences in minority stress risk and protective factors did not mediate most of the differences in mental health and substance use with one exception: higher levels of psychological distress were mediated by the higher levels of internalized negativity to same-sex attractions. The limited explanatory power of the minority stress factors combined with the elevated level of problems of mostly heterosexual individuals call for future studies examining other risk and protective factors

De resultaten van VOCL’89, VOCL’93 EN VOCL’99:vergelijkende analyses van prestaties en rendement

In het schooljaar 1999/2000 is de derde cohortstudie in het voortgezet onderwijs (VOCL’99) begonnen bij ongeveer 20.000 leerlingen die in het voortgezet onderwijs zaten. Van deze leerlingen wordt vanaf de eerste klas de schoolloopbaan gevolgd totdat de leerlingen het voltijd onderwijs verlaten. Het cohort wordt uitgevoerd door het GION in samenwerking met het CBS. Voorafgaand aan dit cohort zijn er nog twee andere cohorten met een vergelijkbare opzet uitgevoerd, namelijk VOCL’89 en VOCL’93. In dit rapport wordt verslag gedaan van de vergelijkende analyses van de schoolloopbanen, de toetsresultaten in het derde jaar en het diplomarendement na zes cohortjaren