EFFECT OF TEMPERATURE ON PERCENTAGE OF GERMINATION OF CANISTEL SEEDS ( Pouteria campechiana )

The canistel is a fruit originated in Mexico and Central America, being introduced in Brazil in 1986. The plants present medium size, however it can reach up to 15 meters of height; the leaves measure about 10 to 25 cm; the flowers are complete and small and the fruit presents yellow coloration when ripe, with whitish pulp and sweet flavor. The propagation can be realized by seed or grafting. In view of almost total absence of information about the culture and the possibility to have a commercial cultivation, the present work, was live in which the effect of the temperature was evaluated in the percentage of germination of the seeds. It was checked that the best averages were obtained in temperature of 30oC and the minor in 15oC, 20oC and 40oC could be considerate the worst of them.


INTRODUCTION
The canistel is a fruit originated in Mexico and Central America, being introduced in several tropical regions of the world (Benza, 1993).In Brazil that introduction was realized by UNESP-Campus of Jaboticabal, in 1986, with material that came from Florida, where it is planted at backyard orchards.The propagation, although is done a lot of times by seed, it can also be done by grafting, allowing the fixation of varieties (Donadio, 1998).
The plant presents medium size, however with great variation could reach up to 15 meters of height.The leaves are alternated, fine and measuring about 10 to 25 cm of length.The flowers are complete and small, happening among the leaves of the newest branches and they are usually produced in the rainy season.The fruit can vary of color, but commonly it is yellow when ripe, with whitish pulp and sweet flavor and when it is green has abundant amount of latex.The ocurrence of seeds on fruit can be just a little or several of them, which are black with 1 to 2 cm of size.
The good climatic conditions for its cultivation are in tropical climates of low altitude to the subtropical ones with 1800 m of altitude and frequent rains.It survives in medium low temperatures from 6 to 8ºC.
In view of almost total absence of information about this fruit, the present work, was realized having as objective to evaluate the effect of the temperature in the percentage of germination of canistel seeds to obtain the largest possible number of seedlings.

MATERIAL AND METHODS
The experiment was conduced in the Laboratory of Seeds, located in the Department of Vegetable Production, of Faculdade de Ciências Agrárias e Veterinárias -UNESP -Jaboticabal -Campus.
The treatments were constituted by six temperatures: 15 º C, 20 º C, 25 º C, 30 º C, 35 º C and 40 º C, writh four repetitions for each one of them and writ 10 seeds by repetition.It was used germinators model BOD MA 402.
The seeds were extracted from ripe fruits of canistel trees, washed, placed to dry on shade and then conditioned in recipients simi-lar to the box type gerbox, having as substrate vermiculita with medium texture.It was done daily evaluation of the number of germinated seeds, in such way that the results were counted in periods of seven days, reaching a total of fourteen weeks in the end of the experiment.The values obtained were compared by average test, more specifically the test of Tukey with 5% of probability.

RESULTS AND DISCUSSION
Observing the Figures 1 and 2 is possible to verify that the best temperature for canistel germination is 30ºC, where 89,42% of the seeds germinated (Tab.1), with a higher germination speed, which allowed it to reach the maximum germination in the smallest time ( 9th week).In the 6th week it already presented more than 70% of germinated seeds, while this same rate was only reached in the 8th week for the treatment of 35ºC and in the 11 th for the treatment of 25ºC.However, there was no significant difference between the treatment of 30 º C and the treatments of 35ºC and 25ºC, which also presented a good percentage of germination of the seeds.Similar results were found by Barbosa et al. (1990) when they studied the influence of the temperatures of 20 º C, 25 º C and 30 º C on seeds EFFECT OF TEMPERATURE ON PERCENTAGE OF GERMINATION OF CANISTEL SEEDS (Pouteria campechiana) germination for cambuci (Paivaea langsdorfii Berg) and uvaia (Eugenia uvalha Meng).They observed that the best temperature for seeds and velocity of germination was the 30 º C.

Treatment
In another research, Barbosa & Barbosa (1985) studied the germination of wild fruits: wax jambu (Syzygium jambos), guamo (Inga edulis) and jatoba (Hymenaea stilbocarpa) in three temperatures (20 º C, 25 º C and 30 º C) and they verified that the guamo seeds presented larger percentage and germination speed on the temperature of 30 º C; for the jatoba there was not significant difference between the temperatures of 25 º C and 30 º C and, for the wax jambu was not observed differences in relation to the tested temperatures.

CONCLUSION
With base in the presented results it can be said that: -the temperature of 30 º C is the best to germinate canistel seeds, reaching the highest percentages of germination and the minor time to get it, what have a real importance for the nurserymen.

FIGURE 1 -
FIGURE 1 -Evolution of the percentages of germination evaluated by week, on different temperatures studied.

TABLE 1 -
Difference by the average of the % of germination obtained when the seeds was maintained on the temperatures in study.