Grandpa's biology - 14









A PLANT SUBJECTED TO DOUBLE 
ATTACK 
BY BOTH FUNGUS
AND
VIRUS.

At first, the fusarium tends to delay the plant's general evolution,
TMV accelerates it: the host's physiological balance
is maintained in a state close to that
of the controls...etc




Reminder: During one experiment, a plant inoculated with fusarium was accidentally contaminated with tobacco mosaic virus. Although the other plants in the same batch displayed the classic symptoms of fusariosis, the plant secondarily inoculated with the virus could not be distinguished externally from the healthy controls, other than by mosaic leaf symptoms. One month later the leaves suddenly turned yellow and fell off; the stems and roots displayed vascular symptoms of fusariosis.





The previous results logically lead to an interpretation of the case of the plant subjected to a double attack by both fungus and virus, as follows: at first, the fusarium tends to change the auxins/gibberellins balance of the aerial organs in favour of auxins (hyperauxinia), but the TMV favours gibberellins (hypoauxinia), and the host's physiological balance is maintained in a state close to that of the controls. With its evolution thus disturbed, the fusariosis only reaches a certain level of severity one month later. The artificially maintained equilibrium is broken, the effects of the fusariosis now reinforce those of the mosaic virus (hypoauxinia in both cases), leading to leaves turning yellow and falling off, evidence of accelerated senescence… (basic metabolism).

Or in other words: at first, the fusarium tends to delay the natural evolution of sugars/nitrogen ratios in the leaves, the virus accelerates it and the host's physiological balance is maintained in a condition close to that of the controls. Thus disturbed in its evolution, the fusariosis only reaches a certain level of severity one month later. The artificially maintained equilibrium is broken (increase in sugars/nitrogen ratios in both cases), leading to leaves turning yellow and falling off, evidence of accelerated senescence (intermediate metabolism).

Or in yet other words: at first, the fusarium tends to delay the plant's general evolution, TMV accelerates it and the host's physiological balance is maintained in a state close to that of the controls. Thus disturbed in its evolution, the fusariosis only reaches a certain level of severity one month later. The artificially maintained equilibrium is broken, the effects of fusariosis now reinforcing those of the mosaic virus (accelerated physiological evolution of the plant in both cases), leading to leaves turning yellow and falling off, evidence of accelerated senescence… (phenotypic aspect)



presentation/contentsa work of popularizationstory of modern biologythe point of view of French citizenssome basic concepts to recallgrandpa's hypothesishow to verify this hypothesisfirst testsevolution of plants according to auxin and gibberellin treatmentshost-parasite relationsaction of the fungus on the plantaction in return of the plant on the fungusaction of the virus on the plantaction in return of the plant on the virusa plant subjected to double attack by both fungus and virusthe scientific debatethe Peter principleconclusion - answer to some questionsimages




Grandpa's biology - 14