Tomato plant leaf ultrastructure
under the effect
brassinosteroid analogue and heat stress conditions
O.Sam ‘/‘, M.Ntifiez T, v. Falch
of
a
$, M.C.de la Rosa $
T Instittuto National de Ciencias Agricolas (INCA), San Jo& de las Lajas, Gaveta Postal No. 1, C.P.
32700, La habana. Cuba.
$ Centro de Ingenieria Gektica y Biotecnologia (CIGB), Apartado Postal 6162, Cubanacan, C.
Habana
C.P. 10600. Cuba.
The different plant species vary in the sensibility and response to environmental stress
(1) that is reflected in the ultrastructure, where i+ produces important changes (2), one of these
important stresses is high temperature.
On the other hand, there are some compounds
as
brassinosteroids, that seem to have a superior influence when plants remain under non-optimal growth
conditions. This function of antistress hormone converts the brassinosteroid into very interesting
products for feasible potential application ; these properties are reported in diverse pubblications (3).
Leaf tissue ultrastructure was studied in tomato plants L. escdentzmnzcv. Campbell-28
cultivated in pots under enviromental conditions. Two treatments with the corresponding control were
applied 15 days after germination. The leaf disks were incubated under laboratory conditions (23OC
day/l8”C night), later they were separated into four groups. Two groups remained under theses
conditions : one of them only with water and the other one with water and Cuban antistress product
BB-6, 0.01 mg/L ; the other groups prepared like the previous ones were submitted to 40°C for 1.5 h,
then the samples were taken and processed to transmition electron micoscopy.
The heat treatment produced important changes in the cell ultrastructure. The most
typical change was the formation of cytoplasmic heat shock granules ; the function of these granules is
said to protect mRNA’s from heat shock-induced degradation. Concerning the leaf disks preincubated
in BB-6 (0.01 mg/L) solution and then subjected to heat shock (4O”C, 1.5 h), granules formation was
also observed in the cytoplasm, but in major quantity than without BB-6 (FIGURE 1).
Another important observation was the accumulation of starch granules in chloroplasts
(FIGURE 2) that is related to the possible natural production of brassinosteroids in plants (4). The
BB-6 decreased cell ultrastructure degradation from heat stress.
References
1.
2.
3.
4.
Bohnert H.J. et. al.. The Plant Cell 7(1995) 1099-l 111, July.
Khokhlova V. and pot-fit-ova S. Physiol. Plantarum 79(1990) 46-47.
Marquardt V. and G. Adam. Chem. Plant Prot. (Review) 7(1991) 103-139.
NuAez M. Los brasinoesteroides y su actividad biologica. La Habana, p.35(1996).
FIG. l- Cytoplasm of mesophyl cells under heat stress conditions without BB-6 showing abundant hat shock
@?l”UkS.’
FIG. 2- Chloroplast of a mesophyl cell with a starch granule and some other litlle granules in the cytoplasm