Passiflora quadrangularis
P. quadrangularis is uncommon at La Selva, with only two wild plants currently known to me in 2014 (both in the successional plots). This species has stiff, four-winged stems and large oval leaves.The petioles bear 6 large nectar glands. Given sun, the plants grow quickly to large size. The fruits are also very large. This is an introduced species cultivated for its large fruit, but is not considered to be invasive. Range: Southern Mexico to Bolivia, Venezuela, the Guyanas, Brazil and Paraguay. Widely found in wet second growth forest, forest edges and along roadsides up to 1000 meters elevation.
P. quadrangularis is cyanogenic when crushed, with values between 0.2 and 5 μM/g plant tissue. According to Spencer 1988, P. quadrangularis contains the simple monoglycoside sulfated cyclopentyl cyanogens Tetraphyllin B sulfate and Epitetraphyllin B sulfate, as well as the complex cyanohydrin compound "Passiquadrangularin". Engler and Gilbert 2007 lists the sulfated compounds only. Smiley and Wisdom (1985) found that P. alata, closely related to P. quadrangularis, also contains substantial amounts of tannins.
HCN measurements of one P. quadrangularis plant in the La Selva garden area suggests the presence of 2 distinct cyanogen release processes, one of which is "fast release" and one "slow release". The fast release system is much like that in other Passiflora species, in that most of the cyanide gets released into the air within 5-10 minutes after crushing the leaf. The slow release process starts right away but releases a constant amount over a 30-40 minute period of time. Measurements suggest that the slow release process is found in new leaves only, and declines to low levels (10-15% of the total) in full sized young leaves and mature leaves that are beginning to harden (see graphs below). The fast release process declines somewhat as leaves mature, and actually rises in quantity as the leaves reach maturity. Plant "behavior" in action! It is interesting to note that P. megacoriacea has an even slower "slow release" process, and lacks fast release entirely. That system is very slow indeed, taking about 2h to fully deplete the measureable HCN, and without an initial peak of release. There is also some evidence that P. ambigua occasionally exhibits a 25-30 minute slow release in addition to its normal fast release process. See text Figures 10 and 11, and Appendix 3 charts A28, A29 and A30 for cyanogenesis measurements from P. quadrangularis.
At La Selva, P. quadrangularis is used as host by H. cydno and probably H. hecale and H. ismenius. Adults of the Black-tibia Flea Beetle (Parchicola "black-tibia") also use this plant, and it is likely that adult Blue Flea Beetles (Monomacra violacea) use it as well. Heliconius ismenius is known to prefer P. quadrangularis as host plant. Could that butterfly species' rarity at La Selva be partly a function of the rarity of P. quadrangularis?
