Effects on Endogenous Hormones in Jujube Fruits under Elevated Temperature and Drought Conditions

  Objective   Effect of elevated temperature and drought stresses on the content of endogenous hormones in jujube fruits was studied.

  Method  In a simulated experiment, 6-year-old Zipiphus jujuba Mill cv. Lingwuchangzao plants were artificially exposed to varied temperatures and restricted water supplies. Ambient atmosphere temperature (T1) and one of 2^oC above it (T2) were applied in combination with a simulated water supply for normal condition in soil (D1), moderate drought (D2), or severe drought (D3). Contents of endogenous hormones (i.e., IAA, ABA, ZT, and JA) in the jujube fruits born from the trees at 7 ripening stages were determined.

  Result  The interactive effect on the hormones by the simulated temperature and drought conditions was significant (P＜0.05). The contents of ABA, IAA, and JA in the fruits were higher when the atmospheric temperature was raised 2 ℃ above normal. Those of ABA, ZT, and JA also became greater under D2, but that of IAA lower, than D1; whereas those of ABA and JA, increased and those of IAA and ZT, decreased under D3.

  Conclusion   The slightly elevated temperature by 2 ℃ seemed to benefit the accumulation of IAA and JA in the jujube fruits, while the drought stress accentuated the temperature effect on the contents of IAA and JA. Water deprivation appeared to benefit ABA and ZT accumulation, and temperature elevation by 2 ℃ promoted the accumulation of ABA but hindered that of ZT.