Appendix
I) Information about the article " Growing Seedlings at less than 1 G "(Carlson. S. 1996. Growing Seedlings at less than 1 G. Scientific American. Febuary 1996. pp.110-111.).
The article, written by Shawn CARLSON, explains the phenomenon of gravitropism and encourages the reader to study these plant reactions by himself, because very few is known already in this domain, especially about what happens, when plants are exposed to a gravity, which is lower than that on Earth, that's to say lower than 1 G ( = 9,81 m/s2).
The author tells us " Something remarkable happens when you tip a plant. Special hormons, called auxins, begin to collect underside of its roots and stem. Auxins stimulate stem cells to grow and divide. The bottom of the stem then outgrows the top, causing the stem to bend skywards. Auxins in the root cells act differently: they retard growth. The auxin-poor cells near the top of the root then outgrow the auxin-rich cells near the bottom, and the root bends downward. In this way, a tipped plant makes internal adjustments to realign itself with the pull of gravity. (...) By the end of the century, scientists had invented a device, called a clinostat, that tricks plants into thinking they are growing in a near-zero-gravity environment. (...) Oddly, professional biologists have paid little attention to what is perhaps the most interesting region to be investigate-between 0 and 1 g. (...) By properly choosing the wheel's rotation speed and placing the seeds at different distances from the pivot, you can germinate seeds at any gravity (...) and see how seeds would grow on Mars. (...) So little work has been done in this area that you can grow just about anything and find something new. I've been focusing on corn. I let the seeds germinate for several days and then measured the total length of the sprouts (when the seeds began to poke out of the pouches, Shawn CARLSON cut the seedlings at their bends and layed all the pieces end to end so that all the bends where in the same direction) and the sum of the bend angles along the stock."
II) Brief history of research on gravitropism.
1700: DODART: first experimentation on gravitropism following the observation that practically every plant on Earth has its stem stretching towards the sky and his roots growing towards the ground.
1727: HALES: continuation of Dodart's studies.
1806: KNIGHT: proof, by means of a clinostat, of the direct effect of gravity on plants.
1854: WIGAND:studies about the effects of gravity and centrifugal force on the growth of roots.
1880: DARWIN: prime studies on auxin, a growth hormone in plants, intervening in gravitropism.
1910: BOYSEN-JENSEN: studies on auxin.
1918: PAAL: studies on auxin.
1929: CHOLODNYS: studies on auxin.
1931: KOGL et HAAGEN-SCHMIT: studies on auxin.
1958: NASA's first space experimentation on plants
1996: WAGNER: interpretation of gravitropism by wave mechanics.