| heal.abstract |
The moisture content (MC) of tomato pollen was conditioned to a range between 3.8% and 53% of fresh weight by equilibration in air with a relative humidity (RH) ranging from 0 -100%. After storage in liquid N (-196°C) for 5 d, followed by thawing and rehydration, germination was measured in vitro on a semi-solid substrate. Pollen with a MC of 6.8% or 9.3%, which was achieved by exposure to 50% or 60% RH, respectively, gave the highest percentages of germination (56.8% and 57.4%, respectively). Further studies involving three MC levels (6.8%, 9.3% and 11.2%, equilibrated at 50%, 60% and 65% RH, respectively) and cryogenic storage for periods of up to 22 months, indicated that both the germination ability and the length of the pollen tubes formed after incubation for 6 h did not depend on the duration of cryopreservation, provided the pollen was rehydrated after thawing. The ability of pollen to set fruit and to produce seeds was not affected by storage in liquid N2 for up to 22 months, when the MC was 6.8% or 9.3%. However, when the MC was 11.2% prior to storage for 14 or 22 months in liquid N2, the percentage of successful pollinations was lower and fewer seeds were formed per fruit. Cumulative O 2 consumption, due to the respiration of pollen during germination, increased linearly with incubation time and the rate of increase was similar for both fresh pollen and pollen that had been stored cryogenically for 6 or 13 months. It is concluded that tomato pollen may be stored in liquid N2 for at least 22 months without loss of viability, provided its MC is adjusted to between 6.5% and 9.5% prior to cryopreservation and that, after thawing, the pollen is rehydrated. |
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