The Adapting Mechanism To Endure Cold Of Three Introduced Palm Species

Palms are widely distributed in tropical and subtropical area, which have been widely introduced into many cities of Southern China for landscape. Cold injury is the most serious factor that limits them to grow in the introduced area.Experiments were conducted to evaluate the adaptation and mechanism to endure cold of Butia capitata Becc, Elaeis guineensis Jacq. and Acoelorraphe wrightii (Griseb.& H. Wendl.) H. Wendl. ex Becc. cultivated in Xiamen Botanical Garden. The results the research were summarized as follows:1.The cold injury index (CI) of palms was proposed to weigh the cold endurance. The results showed that the CI of Butia capitata, Elaeis guineensis and Acoelorraphe wrightii was 7.29, 75.00 and 20.24 respectively. The electrolyte leakage of leaves was measured in October and January under different temperature, and the semi-lethal low temperature (LT₅₀) of leaves was assayed in different sampling period by Logistic equation. The LT₅₀ of Butia capitata., Acoelorraphe wrightii and Elaeis guineensis was -7.93℃,-5.03℃and -2.19℃respectively in October, -19.10℃,-6.60℃and -2.94℃respectively in January. The results showed that the sequence of the cold tolerance was: Butia capitata>Acoelorraphe wrightii >Elaeis guineensis. We can also apply the model of the three palm species in different cities, and can also predict the cold resistance of other palm species.2. The anatomical features of leaves of 3 palm species were surveyed and analyzed firstly. The morphological features of structure were described and stated thoroughly by means of optical microscopy. Calculating the ratio of spongy/palisade tissues, The results of CTR and SR followed the order: Acoelorraphe wrightii>Butia capitata>Elaeis guineensis. and Butia capitata-Elaeis guineensis>Acoelorraphe wrightii, respectively. The results showed the CTR and SR are not related to the cold resistance. The different cold resistance of three palms have different palisade tissues, Therefore, the features of anatomy and structure of leaves should be considered first, then structural quantity be considered secondly to explain the cold resistance.3. The studies on the seasonal changes of extractable total polyphenol content(ETP),soluable condensed tannins(SCT),BCT and total condensed tannins(TCT) content of palm leaves were conducted for the first time. The content extractable total polyphenol content(ETP) of Elaeis guineensis in the four seasons was the lowest, varying from 16.20mg/g to 26.5mg/g. The annual average content of Elaeis guineensis leaves was 21.80mg/g. It was much lower than that of Butia capitata and Acoelorraphe wrightii. From autumn to winter, the range of extractable total polyphenol content(ETP) was in the following order: Elaeis guineensis(1.76mg/g) >Acoelorraphe wrightii(1.24mg/g)>Butia capitata(1.06mg/g).The content of BCT was higher in the leaves of Butia capitata in the spring and summer and autumn.markedly decreased for the Acoelorraphe wrightii and Elaeis guineensis in the winter and autumn. This indicated the Butia capitata with much more efficient photosynthesis, while the decreasing content of Acoelorraphe wrightii and Elaeis guineensis may be related with the low photosynthesis.The high cold resistant Butia capitata had minimum content of total polyphenol content(ETP), soluable condensed tannins(SCT) and total condensed tannins (TCT) in the summer and autumn, in order to reduce the investment for the second-metabolism and to keep more investment for the cold resistance in the winter. However, The content of total condensed tannins(TCT) and soluable condensed tannins(SCT) in Elaeis guineensis leaves was in the maximum in the summer and autumn, This was not a good energy strategy for adapting to the low temperature.4. For the first time to characterize the authentic tannins chemical structure in the mature leaves by MALDI-TOF in palms, The spectra obtained through MALDI-TOF-MS analysis revealed the presence of two series of tannin oligomers. The first series consists of m/z 711-999-1287-1575-1863..., and the second series consists of m/z 727-1015-1303-1591-1879-2167-2455..., and different cold resistant species have the same structure of R₁ and R₂,From this can estimate that there is no relationship between the cold resistance and tannins chemical structure in the palms'cold resistance.5. The gross caloric value(GCV) and ash free caloric value(AFCV) and ash content of different components of three different cold resistant palms were studied for the first time with an oxygen bomb thermometer.The annual average caloric value of Butia capitata was in the following order: mature leaves(20.65kJ/g)>young leaves(19.84kJ/g)>roots(19.55kJ/g)>petioles(18.77kJ/g).The components showed maximum gross caloric value(GCV) in autumn and minimum one in winter. Ash free caloric value(AFCV) varied as same as gross caloric value(GCV). The annual average ash content followed the order: roots(5.14%)>petioles(4.33%)>young leaves(4.21%)>mature leaves(3.97%). The ash content was lower in mature leaves, markedly decreased in young leaves during autumn, and then increased during winter. Seasonal changes of ash content in mature leaves were the same as those in young leaves. Petioles had much lower ash content than roots in winter. Changes in ash content and caloric value of Butia capitata in different seasons reflected the good energy strategy for species with high cold resistance to adapt to the low temperature.The annual average gross caloric value of Acoelorraphe wrightii was in the following order: mature leaves(20.46kJ/g) > young leaves(19.50kJ/g) > roots(19.34kJ/g)> petioles(18.48 kJ/g), There was no significant difference between roots GCV and mature leaves GCV (p>0.05), The GCV of Acoelorraphe wrightii had the same trends of seasons' change as Butia capitata. The annual average ash content followed the order: mature leaves(6.18%)>young leaves(5.19%)>roots(4.84%)>petioles(4.56%). The mature leaves had the highest ash content value.The annual average gross caloric value of Elaeis guineensis was in the following order: mature leaves(19.73kJ/g)>roots(19.33kJ/g)>young leaves(19.06kJ/g)>petioles(18.17kJ/g), There was no significant difference between roots GCV and mature leaves GCV(p>0.05), The GCV of Elaeis guineensis in summer was almost the same as that of autumn. The annual average ash content followed the order: roots(7.01%) > mature leaves(6.78%)> petioles(5.31%)>young leaves(5.28%). The roots and mature leaves had the higher ash content value than those of young leaves and petioles.The gross caloric value was negative correlated remarkably with ash content for young leaves and mature leaves of Butia capitata and Acoelorraphe wrightii, there was only for mature leaves of Elaeis guineensis. Whereas there was no significant negative correlation between gross caloric value and ash content for petioles and roots of the three palms.