| Nitric oxide (NO) is a key signaling molecule in different physiological processes of plants. In the paper, the metabolism of endogenous NO in apple and peach fruits and the effect on aroma biosynthesis were analyzed. The results were shown followed.1. To study the metabolism of endogenous NO in growth and development of apple fruit under normal physiological conditions, the changes of several relative components of NO metabolism including the contents of NO, L-arginine, S-nitrosothiols (RSNOs) and nitrite plus nitrate, the activities of L-arginine-dependent nitric oxide synthase (NOS) and nitrate reductase (NR) were analyzed using vegetal'Gold Delicious'and'Fuji'apples as tested materials. The endogenous NO and L-arginine contents, as well as the L-arginine-dependent NOS activity in young fruit reached the highest value. Endogenous NO production depended on L-arginine-dependent NOS but not NR. The content of RSNOs tended to peak in the fruit enlarging period and then declined. Similarly, the nitrate content increased in early stage of fruit growth, but in late stage, it undulated greatly. Compared to RSNOs and nitrate, the change of nitrite content was in accordance with that of endogenous NO. In general, RSNOs and nitrite could reflect the removal mechanism of NO relatively well.2. The changes of aroma compounds, ethylene release and some enzymes in growth and development of apple fruit were investigated using vegetal'Gold Delicious'and'Fuji'apples as tested materials. The main volatile compounds in'Gold Delicious'apple included hexanol, hexanal, E-2-hexenal, hexyl acetate, E-2-hexenyl acetate and Z-3-hexenyl acetate. The main volatile compounds in'Fuji'apple included hexanol, Z-3-hexen-1-ol, E-2-hexenal, Z-3-hexenal, hexyl acetate, E-2-hexenyl acetate, 2-methylbutyl acetate, Z-3- hexenyl acetate, hexyl butyrate and methyl hexanoate in'Fuji'apple. The ethylene production decreased in early stage of fruit growth, but in late stage, it increased obviously. The variation of ethylene production was related to a change in ACS activity or ACO activity. However, an opposite trend in NO production was shown, and there was a gradual decrease during fruit development and ripening. In general, total alcohols and aldehydes in volatile compounds showed the trends of first increasing and then declining, but total esters tended to rise. Alcohol dehydrogenase (ADH) activity had a similar change to alcohol content, while the upward trends were observed in acyltransferase (AAT) and lipoxygenase (LOX) activities during fruit development. 3. The effect of nitric oxide treatment on the metabolism of endogenous NO and aroma biosynthesis was investigated in'Feicheng'peach fruits during cold storage.'Feicheng'peach fruit at the physiologically mature stage were fumigated with 5 and 10μl l-1 NO gas for 3 hours. Both NOS activity and metabolism productions of NO increased substantially after NO treatment. These results suggested that NO has influence on the metabolism of endogenous NO. The reduction of total alcohols and total aldehydes were obviously delayed, the increase of total esters was delayed by 10μl l-1 nitric oxide treatment. The activities of ADH, AAT and LOX were also inhibited significantly. The effect of 10μl l-1 nitric oxide treatment was better than 5μl l-1 nitric oxide treatment. The treatment of nitric oxide gas (10μl l-1) can maintain higher storage quality of the'Feicheng'peach fruit.4. SPER/NO was synthesized, and the effects of medium, humidity and additives on the release rate of nitric oxide from SPER/NO, as well as the absorption characteristics of nitric oxide by horticultural products were investigated by an electrochemical sensor. SPER/NO was found to release nitric oxide rapidly in acidic media and high humidity, which was delayed by the starch added as filler. Nitric oxide release from SPER/NO was absorbed rapidly by horticultural products, and the rate of absorption in nitrogen was higher than that in air. The tablet was obtained by proportionally mixing SPER/NO with citric acid and starch, and it was found to absorb the moisture from horticultural products and generate nitric oxide slowly.'Feicheng'peach was treaded with SPER/NO tablet and resulted in a certain extension in the postharvest life.
|
PDF Full Text Request