No abstract

The Taxodium hybrid ‘Zhongshanshan 406’ (T. hybrid ‘Zhongshanshan 406’) [Taxodium mucronatum Tenore × Taxodium distichum (L.). Rich] has an outstanding advantage in flooding tolerance and thus has been widely used in wetland afforestation in China. Alcohol dehydrogenase genes (ADHs) played key roles in ethanol metabolism to maintain energy supply for plants in low-oxygen conditions. Two ADH genes were isolated and characterized—ThADH1 and ThADH4 (GenBank ID: AWL83216 and AWL83217—basing on the transcriptome data of T. hybrid ‘Zhongshanshan 406’ grown under waterlogging stress. Then the functions of these two genes were investigated through transient expression and overexpression. The results showed that the ThADH1 and ThADH4 proteins both fall under ADH III subfamily. ThADH1 was localized in the cytoplasm and nucleus, whereas ThADH4 was only localized in the cytoplasm. The expression of the two genes was stimulated by waterlogging and the expression level in roots was significantly higher than those in stems and leaves. The respective overexpression of ThADH1 and ThADH4 in Populus caused the opposite phenotype, while waterlogging tolerance of the two transgenic Populus significantly improved. Collectively, these results indicated that genes ThADH1 and ThADH4 were involved in the tolerance and adaptation to anaerobic conditions in T. hybrid ‘Zhongshanshan 406’.

Taxodium distichum (L.) Rich. var. distichum [baldcypress (BC)], Taxodium distichum var. mexicanum Gordon [Montezuma cypress (MC)], and a Taxodium hybrid (‘Nanjing Beauty’: BC × MC cross, T302) were evaluated for salt tolerance in 2006 at Nacogdoches, TX. Plants were irrigated weekly with four levels of salinity [0, 1, 3.5, and 6 ppt (0, 17, 60, and 102 mol·m−3)] for 13 weeks and then 0, 2, 7, and 12 ppt (0, 34, 120, and 204 mol·m−3) for another 12 weeks. Salinity treatments did not have a significant effect on growth rate; however, there were significant differences in growth rate among the three genotypes. Genotype T302 produced the greatest wet weight, whereas MC had stronger apical dominance and exhibited the greatest increase in height over the course of study. As expected, sodium (Na) concentration in Taxodium leaves increased as sea salt concentrations increased but did not tilt Na/potassium (K) ratios to stressful disproportions. Of the three genotypes, BC exhibited the highest leaf content of Na, calcium (Ca), sulfur (S), and iron (Fe); MC had the lowest leaf content of Na, Ca, S, and Fe; and T302 was intermediate. The benefits of using a hybrid cross (T302) that maintains greater biomass than BC or MC across a range of salinities must be weighed against the potential additional pruning and training necessary for cutting-grown clones relative to BC and MC propagated from seed and flood tolerance relative to BC. Still, combining the best characteristics of different varieties of T. distichum should facilitate the production of favorable genotypes tolerant to a number of soil physical and chemical property fluctuations for arboricultural operations.

The use of electrochemical fingerprints for plant identification is an emerging application in biosensors. In this work, Taxodium ascendens, T. distichum, T. mucronatum, and 18 of their hybrid progenies were collected for this purpose. This is the first attempt to use electrochemical fingerprinting for the identification of plant hybrid progeny. Electrochemical fingerprinting in the leaves of Taxodium spp. was recorded under two conditions. The results showed that the electrochemical fingerprints of each species and progeny possessed very suitable reproducibility. These electrochemical fingerprints represent the electrochemical behavior of electrochemically active substances in leaf tissues under specific conditions. Since these species and progenies are very closely related to each other, it is challenging to identify them directly using a particular electrochemical fingerprinting. Therefore, electrochemical fingerprints measured under different conditions were used to perform pattern recognition. We can identify different species and progenies by locating the features in different pattern maps. We also performed a phylogenetic study with data from electrochemical fingerprinting. The results proved that the electrochemical classification results and the relationship between them are closely related.