1. GRANDPA’S BIOLOGY/ Hormone balance, cell regulation, plant evolution… an approach to biology in which the notions of balance and regulation are considered as two sides of the same problem
2. SOME BASIC CONCEPTS TO RECALL/ Some concepts to recall about biology, chemical reactions, cells, nucleic acids, proteins, enzymes, hormones, sugars/nitrogen ratio.
3. GRANDPA’S HYPOTHESIS/: Balance and regulation, two sides of the same problem? Auxins and gibberellins are thought to act on DNA AT and GC groups, their role being to selectively open the double DNA chains (gene activation) by breaking the H+ bonds wh ich provide stability.
4. HYPOTHESIS VERIFICATION/ How to verify this hypothesis in a particular case chosen at random: existing host-parasite relations between a variety of tomato, a pathogenic fungus and a virus.
5. FIRST TESTS – FUSARIOSIS/ If AG treatments attenuated the visible effects of fusariosis until they disappeared completely, IAA treatments showed an opposite effect in promoting the fusarium attack..
6. PLANT EVOLUTION/ IAA treatments slowed the natural development of leaves and accelerated that of roots… GA treatments had the opposite effect in every case
7. HOST/PARASITE RELATIONS/ The plant represents the environment in which fungus and virus develope – an environment which will be affected by the two parasites – an environment which will affect in return the parasites behaviour.
8. ACTION OF THE FUNGUS ON THE PLANT§/ Initially, fusariosis slows the natural evolution of the plant… The reverse occurs with diseased plant suddenly ageing later on.
9. ACTION OF THE PLANT ON THE FUNGUS/ The behaviour of fusarium in liquid medium vary in function of sugar and nitrogen concentrations – it explains the action of this parasite on the plant.
10. ACTION OF THE VIRUS ON THE PLANT/ The concentration of sugars in the diseased plant increases and nitrogen concentration falls… in other terms, TMV accelerate the natural plant evolution, the plant age..
11. ACTION OF THE PLANT ON THE VIRUS/ By growing, virus uses large quantities of nitrogen – N concentration falls in plant-host tissues – the virus don’t develope normally: relieved of its protein envelope, it is in a latent condition.
12. A PLANT ATTACKED BY BOTH VIRUS AND FUNGUS/ 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
13. CONCLUSION/ Grandpa’s biology in the context of modern biology… Life is like a pair of trousers held up by the braces of the hope!