Análise de diferentes métodos de crioconservação na preservação de sementes de milho (Zea mays L.).

Abstract

This work has had its aim 1) Determining the High Moisture Freezing Limit - (HMFL) from corn seeds and 2) Studying the physiologic quality of 4 varieties of corn seeds (BR-451, BR-201, BR-2121 and CMS-54) put into 3 techniques for cryoconservation ( a) immersion in N 2 L at -196 °C; b) conservation in vapor the N 2 L at -170 °C; c) immersion in N 2 L for one hour and later conservation in chambers at -18° C), 3 defrosting techniques ( a) environment temperature; (b) floating bath at 40° C; c) microwave) and 3 storing periods (3, 30 and 90 days) The experimental outline has been entirely casual, with factorial arrange 4 x 3 x 3 x 3 + 4 (4 varieties x 3 freezing methods x 3 defrosting methods x 3 storing periods + 4 witnesses ), with two repetitions. The statistical analyses have been done by computation program SAS (Statistical Analysis System), version 5, trough Proc GLM (SAS INSTITUTE, 1995) According to obtained results, the conclusions are: a) the meaning o f limit wet for cryoconservation - HMFL, during 3 days for varieties of corn seeds BR-451. BR-201, BR-2121, CMS-54 is around 9% w b ; b) the freezing methods with less effect over germination and strength of corn seeds happened while cryoconservation in vapor of liquid nitrogen (N2L); c) in a general way, corn seeds lose a remarkable percentage o f germination and strength up to 30 days in cryoconservation, and the seeds have got a tendency to keep their physiologic quality after this period of time; d) corn seeds typed BR-451 and CMS-54 crioconserved under liquid nitrogen immersion for 90 days has got a bigger germination percentage while defrosting in room temperature when compared with other defrosting methods (floating and microwave). This can also happen when the BR-451 variety is crioconserved in liquid nitrogen vapor; e) corns seeds, types BR-451, BR-2121 and CMS-54 crioconserved in liquid nitrogen vapor for 90 days have got superior strength percentage ( I s * count) when defrosting in room temperature, when compared to other defrosting methods (floating and microwave). This also happens when varieties BR-201 and CMS-54 are crioconserved in liquid nitrogen immersion.