[Study on ecological suitability regionalization of Eucommia ulmoides in Guizhou].

OBJECTIVE: To study the ecological suitability regionalization of Eucommia ulmoides, for selecting artificial planting base and high-quality industrial raw material purchase area of the herb in Guizhou. METHODS: Based on the investigation of 14 Eucommia ulmoides producing areas, pinoresinol diglucoside content and ecological factors were obtained. Using spatial analysis method to carry on ecological suitability regionalization. Meanwhile, combining pinoresinol diglucoside content, the correlation of major active components and environmental factors were analyzed by statistical analysis. RESULTS: The most suitability planting area of Eucommia ulmoides was the northwest of Guizhou. The distribution of Eucommia ulmoides was mainly affected by the type and pH value of soil, and monthly precipitation. The spatial structure of major active components in Eucommia ulmoides were randomly distributed in global space, but had only one aggregation point which had a high positive correlation in local space. The major active components of Eucommia ulmoides had no correlation with altitude, longitude or latitude. CONCLUSION: Using the spatial analysis method and statistical analysis method, based on environmental factor and pinoresinol diglucoside content, the ecological suitability regionalization of Eucommia ulmoides can provide reference for the selection of suitable planting area, artificial planting base and directing production layout.

Phloem transdifferentiation from immature xylem cells during bark regeneration after girdling in Eucommia ulmoides Oliv.

Eucommia ulmoides Oliv. (Eucommiaceae), a traditional Chinese medicinal plant, was used to study phloem cell differentiation during bark regeneration after girdling on a large scale. Here it is shown that new sieve elements (SEs) appeared in the regenerated tissues before the formation of wound cambium during bark regeneration after girdling, and they could originate from the transdifferentiation of immature/differentiating axial xylem cells left on the trunk. Assays of water-cultured twigs revealed that girdling blocked sucrose transport until the formation of new SEs, and the regeneration of the functional SEs was not dependent on the substance provided by the axis system outside the girdled areas, while exogenous indole acetic acid (IAA) applied on the wound surface accelerated SE differentiation. The experiments suggest that the immature xylem cells can transdifferentiate into phloem cells under certain conditions, which means xylem and phloem cells might share some identical features at the beginning of their differentiation pathway. This study also showed that the bark regeneration system could provide a novel method for studying xylem and phloem cell differentiation.

Opposite patterns in the annual distribution and time-course of endogenous abscisic acid and indole-3-acetic acid in relation to the periodicity of cambial activity in Eucommia ulmoides Oliv.

The seasonal change of free abscisic acid (ABA) and indole-3-acetic acid (IAA) and their relationship with the cambial activity in Eucommia ulmoides trees were investigated by ABA and IAA immunolocalization using primary polyclonal and rhodamine-red fluorescing secondary antibodies, ABA and IAA quantification using high performance liquid chromatography (HPLC), and systematic monitoring of vascular cell layers production. ABA and IAA clearly displayed opposite annual distribution patterns. In the active period (AP), both immunolocalization and HPLC detected an abrupt decrease of ABA, reaching its lowest level in the summer. During dormancy, ABA started increasing in the first quiescence (Q1) (autumn), peaked in the rest (winter), and gradually decreased from the onset of the second quiescence (Q2) (the end of winter). IAA showed a reverse pattern to that of ABA: it sharply increased in AP, but noticeably decreased from the commencement of Q1. Longitudinally, the ABA distribution increased apico-basally, contrasting with IAA. Laterally, most of the ABA was located in mature vascular tissues, whereas the IAA essentially occurred in the cambial region. The concomitant IAA-ABA distribution and seasonal changes in vascular tissues greatly correlated with xylem and phloem cell production, and late wood differentiation and maturation. Interestingly, the application of exogenous ABA to quiescent E. ulmoides branches, in a water-culture system, inhibited external IAA action on cambial activity reactivation. These results suggest that, in E. ulmoides, ABA and IAA might probably interact in the cambial region. The annual cambial activity could be influenced by an IAA:ABA ratio; and ABA might play a key role in vascular cambium dormancy in higher plants. The relationship between hormonal changes and the (particular) annual life cycle of E. ulmoides is also discussed.

Relationship between endogenous indole-3-acetic acid and abscisic acid changes and bark recovery in Eucommia ulmoides Oliv. after girdling.

Eucommia ulmoides (Eucommiaceae), a traditional Chinese medicinal plant, is often subjected to severe manual peeling of its bark. If the girdled trunk is well protected from desiccation, new bark forms within 1 month. It has been proposed that phytohormones play a key role in this process. Research has been conducted to determine the distribution of endogenous indole-3-acetic acid (IAA) and abscisic acid (ABA) during the bark recovery, using high-performance liquid-chromatography (HPLC) and fluoro-immuno-localization techniques. Results showed that, from 2 d after girdling, the IAA content in the recovering bark (RB) increased markedly while that of ABA decreased. The opposite pattern was observed during progressive re-establishment of the tissues. Immuno-localization showed that most of the IAA was located in the RB tissue layers undergoing cell division, dedifferentiation and (re)differentiation, such as xylary rays, immature xylem, phellogen and cambial regions. This study also provides evidence that IAA and ABA are involved in the bark reconstitution.

Time-course of programmed cell death during leaf senescence in Eucommia ulmoides.

Leaves of Eucommia ulmoidesOliv. harvested between April to November were examined for programmed cell death (PCD) during growth and senescence. Leaves developed in April, becoming fully expanded in late May, remaining unchanged until November when they started to dehisce. Falling leaves retained a green color. Our results showed that (1) mesophyll cells gradually reduced their nuclei from September to November, (2) positive TUNEL signals appeared on the nuclei from August, (3) ladder-like DNA fragmentation occurred in September and October, and (4) a 20-kDa Ca(2+)-dependent DNase appeared in these same months. In fallen leaves, intact mesophyll cell nuclei could not be detected, but a few cells around the vascular bundle had nuclei. Therefore, (1) programmed cell death (PCD) of leaf cells occurred in the leaves of E. ulmoides, (2) the progress of mesophyll cell PCD lasted for more than 2 months, and (3) PCD of leaf cells was asynchronous in natural senescing leaves.