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This shows a curious problem on P. amethystina which I have given the
temporary label of the 'Black Death'. Note
that the name is a bit deceptive in that it is the affected tissue that
dies not the plant itself! Also it is not
infectious.It happens as a result of tissue
necrosis in some Passiflora once the vascular water transport system to
that particular part fails. In this particular instance, by its pattern,
leaf scorch may have triggered it. Note in the leaf above that the veins
are still OK. Dr. John MacDougal comments that 'It clearly is an internal
physiological (abiotic) reaction.' Black Death indicates that a particular bit of tissue is dead but does not indicate that the plant itself will necessarily die. If its growing conditions improve the Black Death will not travel further. It has also been observed on closely related species such as P. loefgrenii 'Corupa' and P. loefgrenii 'Iporanga'. It can also be found on the hybrid offspring of these species such as P. amethystina x P. caerulea, P. 'Purple Haze', but the crossing considerably reduces the problem. My hypothesis as to what might be going on is here. |