The watercress glucosinolate-myrosinase system: a feeding deterrent to caddisflies, snails and amphipods.

Watercress (Nasturtium officinale) possesses the glucosinolate-myrosinase system. This system is regarded as a classic example of chemical defense for terrestrial crucifers. Damage of watercress initiates myrosinase-mediated hydrolysis of phenylethyl glucosinolate to a toxic endproduct, phenylethyl isothiocyanate.

Watercress and amphipods Potential chemical defense in a spring stream macrophyte.

We investigated the potential role of defensive chemicals in the avoidance of watercress (Nasturtium officinale) by the cooccurring amphipod,Gammarus pseudolimnaeus at two spring brooks: Carp Creek, Michigan and Squabble Brook, Connecticut. We conducted observations and laboratory experiments on the consumption of watercress, the toxicity of damaged (frozen) watercress, and the toxicity of damage-released secondary chemicals. Field-collected yellowed watercress typically lacked the bite and odor characteristic of green watercress and was consumed byG.

Glucocapparin variability among four populations ofIsomeris arborea Nutt.

Glucocapparin (methylglucosinolate), a putative defense compound, was found to vary between desert and nondesert populations ofIsomeris arborea (Capparaceae): Plants from desert populations contained greater concentrations than nondesert plants in four of the five organs analyzed. Immature leaves at desert sites had average glucocapparin concentrations of 9.2 mg/g and 8.

Isolation and characterization of glucocapparin inIsomeris arborea nutt.

Isomeris arborea (Capparaceae), is the only woody caper endemic to southern California and northern Baja. Methylglucosinolate, also known as glucocapparin, was the only glucosinolate found inI. arborea organs by paper chromatography of the thiourea derivatives and was quantitatively determined by gas chromatography by hydrolytic products.

Seasonal Shifts of Photosynthesis in Portulacaria afra (L.) Jacq.

Portulacaria afra (L.) Jacq., a perennial facultative Crassulacean acid metabolism (CAM) species, was studied under natural photoperiods and temperatures in San Diego, California.