Changes of signal substances of tomato seedling quality decline under storage and transport conditions

The experiment demonstrated that light and water stress evidently increased Ca²⁺-ATPase in the third leaf of tomato seedlings. Ca²⁺-ATPase, through conversion of extra- and intra-cellular signal substances, synchronized the adversity stress confronting tomato seedlings in transport and storage with the protective reaction of the seedlings themselves and united upstream and downstream events. Results indicated that the signal system of seedlings in transport and storage showed apparent and oriented changes under adversity. In this experiment, abundant ethylene release was detected in the treated group since the 3rd day of transport and storage, and the release rose abruptly on the 4th—6th day. This hormone, upon arrival at the receptor, through signal transduction, activated the second signal system, which, after undergoing multistage amplification, was strong enough to inhibit the synthesis of proenzyme, thus crippling the function of the regulatory enzyme system. In this experiment, the representative enzyme of the second signal Ca²⁺-ATPase and its related substance CaM were very active at early stage of transport and storage, but later their activity decreased. The disarray of the second signal led to the sending of wrong signals, thus causing damage to the cells. This was the internal factor of decay entailed by environmental stress.