杜仲形成层活动周期中多糖贮量和淀粉酶同工酶的变化

杜仲(Eucommia ulmoides)枝条中的多糖颗粒经Ⅰ-KI溶液染色不显蓝黑色反应,偏光显微镜检查也不显示各向异性。髓、木质部、木射线和皮层薄壁细胞内多糖贮量的变化和形成层的活动周期有关:从5月下旬至12月中旬,逐步积累:从12月下旬至翌年4月中旬则逐步消失。韧皮部薄壁细胞中的多糖颗粒很少,而且没有季节性变化。淀粉酶同工酶酶谱在不同组织中不同,并随形成层的活动状态而变化,但与多糖颗粒的积累和消失无相关关系。     

豌豆顶芽衰老过程中的显微、超微结构和nDNA的变化

显微、超微结构研究表明 ,短日照条件下豌豆顶芽的衰老过程是从营养生长锥向花芽的转化 ,而用DNA原位末端标记 (TUNEL)、Caspase 8WesternBlot和 14 0bpDNA片断积累的试验结果证明 ,转化为花芽的整个生长锥细胞发生了编程性死亡 (PCD) ,而且其最顶端部分细胞首先发生PCD ,而顶端周围的分生组织细胞逐渐分化出花芽的各部分 ,但顶芽最后并没有发育成为完整的花 ,所有细胞就都发生PCD ,从而顶芽衰老     

Temporal and spatial changes in Ca2+ distribution during the programmed cell death of tracheary elements

The changes in Ca²⁺ distribution in the tracheary elements (TEs) of the pepper leaves were studied using the cytochemical method of potassium antimonate. At the early stage of TEs formation, the vacuole and the nucleus held large volume, and antimonate Ca²⁺ deposits were observed mainly in the intercellular space and the cell wall. As the thickening of secondary wall occurred, the vacuole, nucleus and other organelles began to rupture, concomitant with the increase of calcium deposits in the cytosol, showing the influx of Ca²⁺ into the cell. With the further rupture of cytoplasm and other organelles, the number of calcium deposits at the non-thickening cell wall increased, but declined at the thickening bands of the secondary wall. When the cytoplasmic contents disappeared completely, the level of Ca²⁺ decreased at the non-thickening wall, but by contrast, increased at the thickening bands of the secondary wall. These observations indicated that the dynamic changes in Ca²⁺ distribution spatially and temporarily might have a close correlation with its distinct roles played during the formation of the secondary walls.     

Programmed cell death in Laminaria japonica (Phaeophyta) tissues infected with alginic acid decomposing bacterium

TdT-mediated dUTP-biotin nick end labeling (TUNEL) is a sensitive and valid method for detecting DNA cleavage in programmed cell death (PCD). Using this method, DNA cleavage was observed in Laminaria japonica sporophytic tissues, which were infected with alginic acid decomposing bacterium. It was found that DNA cleavage occurred 5 min after the infection, the fragments with 3′-OH groups of cleaved nuclear DNA increased with time of infection and spread from the infection site. Although no typical DNA ladder (200 bp/180 bp) was detected by routine agarose gel electrophoresis, the cleavage of nuclear DNA fragments of 97～48.5 kb could be detected by pulsed field gel electrophoresis (PFGE). By using CaspGLOWTM fluorescein active caspase-3 staining method, caspase-3 activity has been detected in response to the infection of alginic acid decomposing bacterium. Our results are similar to the observations in hypersensitive response (HR) of higher plant, suggesting that the rapid cell death of L. Japonica infected by alginic acid decomposing bacterium might be involved in PCD, and indicating that the occurrence of PCD is an active defense process against the pathogen's infection.     

Programmed cell death involved in the schizolysigenous formation of the secretory cavity in <Emphasis Type="Italic">Citrus sinensis</Emphasis> L. (Osbeck)

The developmental types of secretory cavities in Citrus remain unclear and whether or not programmed cell death is involved in the developmental process of secretory cavities remains an enigma. Regarding cavity formation in Citrus sinensis fruits, this work uncovered novel evidence to delineate secretory cavity formation in schizolysigeny, supporting the possibility of utilizing secretory cavities as a new cell biology model for investigating the molecular mechanism of plant programmed cell death.     

Constitutive activation of AtMEK5, a MAPK kinase, induces salicylic acidindependent cell death in Arabidopsis thaliana

In most circumstances, plants are able to defendthemselves against pathogen attack. The mechanisms ofplants resisting the invasion of pathogens often includeinduction of hypersensitive response (HR) cell death, theactivation of defense genes and the production of antim-icrobial phytoalexins[1—3]. Plant defense responses are ini-tiated either by the interaction between a plant resistance(R) gene and a pathogen avirulence (avr) gene or by thebinding of a non-race-specific elicitor to its recep…