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.

Wood formation is a complex process composing many biological events. To access its key developmental stages, we have established a regeneration system that can mimic the initiation and differentiation of cambium cells for Chinese white poplar. Anatomical studies showed that new cambium and xylem re-appeared in sequence within a few weeks after being debarked. This provides the opportunity to follow key stages of wood formation by sampling clonal trees at different regeneration times. We used this system in combination with a proteomic approach to analyze proteins expressed in different regeneration stages. PMFs for 244 proteins differentially displayed were obtained and queried against public databases. Putative functions of 199 of these proteins were assigned and classified. Regulatory genes for cell cycle progression, differentiation and cell fate were expressed in the formation of cambial tissue, while 27 genes involved in secondary wall formation were predominantly found in the xylem developing stage. This indicates that the change of gene expression pattern is corresponding to the progression of second vascular system regeneration when and where the key events of wood development occur. Further exploration of these interesting genes may provide insight into the molecular mechanisms of wood formation.

PPF1 encodes a putative calcium ion carrier that affects the flowering time of transgenic Arabidopsis by modulating Ca2+ storage capacities in chloroplasts of a plant cell. In the current work, we found that differential expression of PPF1 might affect processes of programmed cell death (PCD) sinceDNAfragmentationwas detected in senescencing apical buds of long day-grown G2 pea (Pisum sativum L.) plants, but was not in non-senescencing short day-grown counterparts at all growth stages. An animal inhibitor of caspase-activated DNase (ICAD) homologue was detected in short day-grown plant continuously throughout the whole experiment and only in early stages of long day-grown pre-floral G2 pea apical buds. DNA fragmentation was significantly inhibited in apical meristems of transgenic Arabidopsis that over-expressed the PPF1 gene when compared to that of either wild-type control or to PPF1 (−) plants. The expression of ICAD-like protein decreased to undetectable level at 45 dpg in apical tissues of PPF1 (−) Arabidopsis, which was much earlier than that found in PPF1 (+) or wild-type controls. In epidermal cells of PPF1 (−) plants, we recorded significantly earlier calcium transient prior to PCD. We suggest that the expression of PPF1, a chloroplast localized Ca2+ ion channel may inhibit programmed cell death in apical meristems of flowering plants by keeping a low cytoplasmic calcium content that might inhibit DNA fragmentation in plant cells.

Eucommia ulmoides Oliv. is strictly a dioecious perennial tree native to China. The pistillate plants are economically more useful than the staminate plants. The random amplified polymorphic DNA (RAPD) technique was used to screen markers of sex determination in this species.A569 bp RAPD marker, marker linked to sex determination in E. ulmoides (MSDE), was found in all the pistillate but not in the staminate plants; its exclusiveness to pistillate plants was confirmed by Southern blotting. MSDE was sequenced and specific primers were synthesized to generate a 569 bp pistillate-specific SCAR marker, SCARmr. SCARmr could be useful for screening E. ulmoides plants for gender even before they reach reproductive maturity, resulting in considerable saving of time and economic resources.

通过电子显微镜观察、DNA断裂检测及类似半胱氨酸蛋白酶（caspase-like proteases，CLPs）降解检测等技术，对杜仲（Eucommia ulmoides Oliv.）次生木质部分化过程的细胞编程死亡进行了研究。分化中的次生木质部细胞总DNA凝胶电泳检测到DNA ladder，并通过TUNEL检测进一步确定了DNA被降解。Western blot结果表明：caspase-8和caspase-3状蛋白酶（caspase-8-和caspase-3-like proteases，CLPs）及多聚ADP-核糖聚合酶（poly（ADP-ribose） polymerase，PARP）在次生木质部分化过程中被降解。这些研究结果表明，杜仲次生木质部的细胞分化是一个典型的编程性死亡（Programmed cell death，PCD）过程，CLPs可能参与了此过程。

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 fluoroimmuno-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.

对杜仲（Eucommia ulmoides Oliv.）一年生枝条休眠中的芽和维管形成层的结构和蛋白质含量进行了研究，探讨了杜仲不同休眠期转化的生理生化机理。结果证实了杜仲树的休眠期包括2个被动休眠期和一个生理休眠期。在生理休眠期，无论用外源IAA处理，还是给予适当的温度和光照，形成层都不能恢复活动。而且，雌株进入各个休眠阶段的时间都比雄株早。树皮中的蛋白质含量在第一被动休眠期间（Q1）显著地逐步增高（P<0.01），进入生理休眠期（R）后，急剧降低，但第二被动休眠期（Q2）开始后又显著升高（P<0.01）。杜仲雌雄株树皮中的蛋白质含量变化趋势基本一致，但雄株发生变化的时间比雌株早。SDS-PAGE电泳结果表明，在Q12R2Q2的转变期出现-11.8kD的特异蛋白条带。此特异蛋白条带可能与形成层休眠期中各阶段的转变调节有关。

PPF1 is a gibberellin-induced, vegetative growth-specific gene, first isolated from short-day (SD)-grown G2 pea plants. In the current work, we found that transgenic Arabidopsis plants overexpressing the PPF1 gene (PPF1 (+)) flowered much later and had a significantly longer lifespan compared to control plants, whereas suppression of this gene (PPF1 (-)) resulted in a very rapid reproductive cycle. Western blotting analyses of PPF1 (

Leaves of Eucommia ulmoides Oliv. 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 Ca2+-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.

The bamboo, woody monocot, has two types of parenehyma cells in the ground tissues of its culm, in contrast to a single type of parenchyma cell in rice, maize and other major crop species. The distribution of cell wall components, including lignin, (1→3), (1→4)-β-α-glucans (MGs), the highly-substituted glucuronoarabinoxylans (hsGAXs) and low-branched xylans (IbXs) in ground parenchyma tissue of Phyllostachys heterocycla vat. pubescens culms was studied at various developmental stages using light microscopy (LM), UV-microscopy, transmission electron microscopy (TEM) and immunolabeling techniques. The short parenchyma cell walls were lignified in 2-month-oId bamboo culms just as the long parenchyma cell walls were. The lignified regions were confined to the portions in contact with the long parenchyma cell walls, while the walls at the cell corner region never lignified, even in 7-year-old culms. Significant differences were also found in the hemicellulose distribution between the short and long parenchyma cell walls. In bamboo parenchyma tissue, MGs were localized in short parenchyma cell walls and few were found in long parenchyma cell walls in both young and 7-year-old culms. The distribution of hsGAXs was similar to that of MGs in young culms, but they only appeared in the cell corner region of short parenchyma cells in old culms. Low-branched xylans were distributed in the lignified, hut not in unlignified parenchma cell walls. Based on this evidence, the differences of function in both short and long parenchyma cells in a bamboo culm are discussed.