Effects Of Salinity On Tannin Production Of Casuarina Species And Allelopathy

Tannins known as the group of phenolic compounds are the significant plant secondary metabolites. They occur widely in Casuarina species, and have important nutritional and physiological consequences. The effect of different drying temperature on estimates of polyphenolics and condensed tannins of two Casuarina species (Casuarina glauca and Casuarina cunninghamiana), tannins level in international provenances of Casuarina equisetifolia, salinity effects on tannin production of Casuarina equisetifolia and allelopathy were studied in this paper.The results showed as follows:1. Under the different drying temperature (40℃, 60℃, 80℃, and 105℃), contents of the total phenolics and condensed tannins changed with drying temperature. The drying temperature for the highest extraction of total phenolics was at 60℃for C. glauca and 80℃for C. cunninghamiana, respectively. While the drying temperature for highest extraction of extractable condensed tannins was at 80℃for C. glauca, 60℃for C. cunninghamiana, respectively. But the pattern of protein- and fiber- bound condensed tannins was the identical, namely increased with temperature.2. The content of total phenolics, extractable condensed tannins and bound condensed tannins were analyzed on the 33 international provenances of C. equisetifolia. The content of total phenolics in Oceania provenances of C. equisetifolia were lower than that in Africa and Asia provenances; the extractable condensed tannins of Africa provenances were higher than that of Oceania and Asia; bound condensed tannins of different provenances of C. equisetifolia showed not significant differences from each other at P > 0.05. Three good provenances, namely, the 23rd (Malaysia), the 5th (India), the 30th (Thailand) were selected according to the above analyses.3. Effects of salinity (0‰, 2‰, 4‰, 6‰, 8‰and 10‰) on tannins production of C. equisetifolia cutting seedlings were conducted. During the period of different salinity culture (45 d), total phenolics, extractable condensed tannins, protein- and fiber- bound condensed tannins of the seedlings increased and reached the highest at salinity 10‰. No significant differences were found among total phenolics, extractable condensed tannins and total condedsed tannins of C. equisetifolia on different salinity culture from 60 d to 75 d. The tannins contents and protein precipitation capacity fluctuated from 90 d to 105 d. These observations suggested that salinity had no great effect on tannins production of C. equisetifolia cutting seedlings during the culture.4. The crude extracts of tannins from C. equisetifolia branchlets had significant allelopathy effect on the C. equisetifolia seedlings. They can inhibit the growth of the seedlings. The significantly negative correlations were found between total phenolics, condensed tannins, and total condensed tannins of seedlings with the increasing concentrations of crude extracts of tannins, except for bound condensed tannins.