Abstract:

To investigate the harvest date as well as its biological basis for the preservation of green walnut (Juglans regia L.)
fruits, walnut fruits cv. Xifu 2 were picked on three time points Ⅰ (August 23), Ⅱ (August 29) and Ⅲ (September 4) and
stored at −1–1 ℃ and a relative humidity (RH) of 70%–80%. Fruit decay and postharvest biological indices of the green
husk were measured at 6-day or 9-day intervals. The first respiration peaks of fresh fruits from harvest date Ⅰ, Ⅱ and
Ⅲ occurred after,during and before the harvest point and correspondingly,begin,proceeded and finished in the first 6 d of
storage. The second respiration peak and ethylene release peak appeared earlier for stored fruits from later harvest date.
After 45-day storage, decay index (DI, 31.47%) of fruits from date Ⅰ was significant higher than that from date Ⅱ (17.8%),
which was significant higher than that observed for date Ⅲ (12.7%) (P < 0.05). On the harvest dates, abscisic acid (ABA)
content of the green husk was higher and indole acetic acid (IAA), gibberellin (GA) and zeatin (Zr) contents were lower
in comparison with that throughout the postharvest period. The contents of all 4 hormones tested rose in the final stage in
response to ethylene peak. In conclusion, harvest date Ⅲ is suitable for the preservation of Xifu 2 walnut with green husk
and maturation on the tree and senescence during storage of the fruits are possibly related to increased levels of ABA content
and ethylene release, respectively.

Key words: green walnut fruit, harvest date, cold storage, postharvest physiology, hormone