The Changes of Photosynthetic Properties and Cell Microstructure in Peanut Leaves during Leaf Senescence

The changes of photosynthetic properties and cell microstructure in peanut leaves during leaf senescence were studied with two high-yielding peanut cultivars (cv. Luhuall and Fu8707). The main results showed that during the whole process of leaf growth and senescence, changes in the photosynthesis rate (Pn) and contents of chlorophyll in leaves, could be described with a parabolic function, y = A + Bx + Cx2 (where y refers to the values of the above parameters and x to the days after leaf unfolding). During peanut leaf senescence , the shape of chloroplast changed gradually from long ellipses to circles.The starch globule in chloroplast altered gradually from more and larger sizes to fewer and smaller, but the oil globule from fewer and smaller to more and larger. The grana lamellae varied progressively: from thinness and length to thickness and shortness; from ranking along the long axle direction of chloroplast to disorderly arrangment and finally blurring. At last, the membrane envelope of chloroplast broke, so the inclusion seeped out to the cell and the chloroplast broke up.

Photosynthetic properties of the mid-vein and leaf lamina of field-grown, high-yield hybrid rice during senescence

Previous studies with rice(Oryza sativa L.) have shown that the different components of the photosynthetic apparatus are not uniformly synthesized or degraded during senescence. However, while most of those studies have focused on the leaf lamina, few have addressed senescence-associated chloroplast function or leaf physiology. Here, we investigated the photosynthetic properties of the mid-vein and leaf lamina in a high-yield hybrid rice cultivar(Liangyoupei 9, LYP9) during the senescence stage. Assimilation and transpiration decreased more slowly in the mid-vein than in the lamina during senescence, suggesting more sustained photosynthesis in the mid-vein, as well as stronger heat dissipation. Two-dimensional gel electrophoresis suggested that photosynthesis and energy metabolism were less affected by senescence in the mid-vein than in the leaf lamina. During late senescence, the excess energy dissipation in the midvein through the xanthophyll cycle had a higher active photosynthetic capacity than in the leaf lamina, and we inferred that the mid-vein and leaf lamina of LYP9 rice differed in terms of their maturation. Taken together, these results provide new insights into the underlying mechanisms of senescence of the rice mid-vein and associated physiology.

Comparative Analysis of the Photosynthetic Characteristics and Active Compounds of Semiliquidambar cathayensis Chang Heteromorphic Leaves

In the present study,the variation patterns of leaf shape in different populations of individual Semiliquidambar cathayensis plants were analyzed to investigate the relationship among leaf shape variation,photosynthetic properties,and active compounds to understand the genetic characteristics of S.cathayensis and screen elite germplasms.The leaf shape of 18 offspring from three natural S.cathayensis populations was analyzed to investigate the level of diversity and variation patterns of leaf shape.Furthermore,photosynthetic pigment content,physiological parameters of photosynthesis,and the active compounds in leaves of different shapes were determined.Statistical analysis showed that the leaf shape variation in S.cathayensis indicated a high level of genetic diversity among and within the populations.Cluster analysis showed that the three natural populations formed two clusters,one whose offspring was dominated by entire leaves and another characterized by palmately trifoliate leaves.The differences in photosynthetic characteristics and active compounds of leaves of three different shapes were comprehensively evaluated using principal component analysis.Two principal components with a cumulative contribution rate of 92.768%were extracted,of which the highest comprehensive score was for asymmetrically lobed leaves.The leaf shape in different S.cathayensis germplasms exhibited distinct patterns,and there were some correlations between the photosynthetic properties and active compounds in leaves of different shapes.Thus,the leaf shape can be used to predict active compound content,and in turn,select varieties based on that purpose;it also provides a simple and effective method to classify S.cathayensis germplasms.

Cloning and Characterization of the fecC Gene Necessary for Optimal Growth under Iron-Deficiency Conditions in the Cyanobacterium Anabaena sp. PCC7120

ThefecC gene encoding a putative iron (III) dicitrate transporter was cloned from nitrogen-fixing cyanobacteriumAnabaena sp. PCC 7120, and inactivated. The mutant grows normally in medium with NO 3 ? , NH 4 + or without combined nitrogen. But in iron-deficient medium, the mutant grows slowly. Photosynthetic properties were compared between the mutant and the wildtype strain, the content of photosynthetic pigments in the mutant is lower than that of the wild-type. The results of RT-PCR experiments show that thefecC gene is expressed under iron-deficient conditions, but is not expressed under iron-replete conditions. These results revealed thatfecC gene product is required for optimal growth under iron-deficient conditions inAnabaena sp. PCC 7120. Key words Anabaena sp. PCC 7120 - fecC - iron deficiency - photosynthetic properties - expression CLC number Q 933 Foundation item: Supported by the National Natural Sciences Foundation of China (30070154), the Frontier Science Projects Program of the Institute of Hydrobiology, the Chinese Academy of Sciences (220316), State Key Project on Cyanobacterial Bloom Control in Lake Dianchi (K99-05-35-01)Biography: XU Wen-liang (1974-), male, Ph. D, research direction: molecular genetics of cyanobacteria.