Efeito de condicionamento mecânico no controle de porte e qualidade de crisântemo evasado.

The chrysanthemum (Dendranthema grandiflorum Ramat Kitam.) is an original plant of Japan belonging to Asteraceae family. It is one of the most marketed ornamental plants, for three main reasons: response precision to the photoperiod, diversity of types and colors of flowers and durability of the flower. The chrysanthemum cultivation in vase demands, besides the pruning, the use of regulators for the more effective control of the height. Researchers are “trying to substitute the use of chemical substances to regulate the growth by the use of mechanical conditioning”, that would be done through a physical disturbance in parts of the plant resulting in a mechanical response to this stress, that usually comes in the form of inhibition of the growth in mass and dimension of most of plants parts. The present experiment had as objective to study the influence of stress, comparing to a growth regulator to control chrysanthemum height. The work was installed in pots under greenhouse conditions (Vegetal Production Department -Horticulture, FCA/Unesp), in March of 1999. The plants were submitted to the following treatments: T1 = witness; T2 = SADH (succinic acid – 2.2- dimethyl hydrazide) (0,25%); T3 = mechanical stress, starting from the fourth week, once a day; T4 = mechanical stress, starting at the fourth week, twice a day; T5 = mechanical stress, starting at the sixth week, once a day; T6 = mechanical stress, twice a day. The results, led to the following conclusions: the stress decreased significantly the height of the plants; the precocious application of the stress increases the response, and this presents a larger response as larger the amount of stress applied daily; SADH was the treatment that produced the smallest plants; the stress, didn’t have deleterious effect in the qualitative parameters of the plants (production of flowers and leaves), that is, didn’t decrease the quality of the produced plants.