Ascorbate peroxidase (APX) plays a crucial role in the detoxification of hydrogen peroxide. APX activity is maintained significantly higher in the paraquat­treated leaves of the paraquat-tolerant Rehmannia glutinos. This study was conducted to understand structural and regulatory characteristics of APX gene in R. glutinosa. A putative APX cDNA clone (RgAPX1) was isolated from a leaf cDNA library using a partially sequenced expressed sequence tag clone. RgAPX1 is consisted of 1148 bp nucleotides and contains an open reading frame encoding a 250 amino acid-long polypeptide. Deduced RgAPX1 amino acid sequence shares higher sequence similarity to cytosolic APXs. RgAPX1. expression was higher in the leaf than in the flower and root. Southern blot result indicates the presence of one or two RgAPX1-related genes in R. glutinosa genome. RgAPX1 transcription was affected differentially by various stresses and phytohormone. The results indicate that RgAPXl is constitutively expressed in most tissues and its expression is modulated for the immediate and efficient detoxification of H2O2 under normal and stress conditions.

Thirty-nine out of eighty-five barley varieties/strains survived until heading stage in the saline experimental field (0.03-0.05~%~;salt) and they were used for pollen study. Light and scanning electron microscopic observations revealed two distinctive types of barley pollens: one transparent and small in size and the other dark and larger. In addition, both types of pollens were stained with Alexander's stain and it was found that the smaller and transparent pollen was cytoplasm-devoid (CD) while the larger pollen was cytoplasm-rich (CR). Sixteen out of 39 barley varieties/lines grown in the saline soil had CR pollens, which were rarely observed in the barley plants grown in the non-saline soil. Moreover, it was observed that salt stress severely reduced seed setting in the varieties having degenerated pollens. These results suggest that salt stress affects the fertility of barley pollen. The sterile pollen was undersized and lack of cytoplasm probably due to abortion. Furthermore, a varietal difference existed in the response of pollen development to salt stress.

Phosphorus (P) is a macronutrient playing important roles in many plant processes. Significant interest has been devoted to search and utilize genotypic variations in P use efficiency in rice but with little effort to understand its physiological and biochemical bases. In this study, we examined responses to P deprivation of some primary and secondary traits in 3-week-old seedlings of the three genotypes, Sobi-byeo (japonica), Dasan-byeo (japonica ~times indica) and Palawan (indica). In general, percent weight due to root was increased up to 26%, but amounts of root protein and proteins secreted from roots were decreased by 11 to 19% and 31 to 51 %, respectively, by 3 to 21 days of P deprivation in the three genotypes. Interestingly, however, responses of Palawan to short-term P deprivation were contrasting to those of Dasan-byeo and Sobi-byeo in seedling weight and contents of shoot protein, chlorophyll and anthocyanin. Seedling weight was not decreased, but shoot protein content was decreased in P-deprived seedlings of Palawan. Contents of chlorophyll in leaves and anthocynin in roots were increased in Dasan-byeo and Sobi-byeo, but decreased in Palawan. The results suggest that responses of protein and pigment synthesis to P deficiency are different in modem and traditional varieties and the difference may at least in part be due to the selection for high yield under highly fertilized conditions.

The content and composition of tocopherol were analyzed in peanuts produced in Korea. The tocopherol assay was consisted of an extraction with n-hex-ane:isopropanol mixture followed by high pressure liquid chromatography with fluorescence detection. Tocopherol content was higher in leaves and seeds but lower in seed coats and shells. α -/~gamma - Tocopherol ratio was as low as 0.53 in seeds and as high as 22.5 in shells. Tocopherol content in seeds of nine varieties ranged from 142 to 220 ng/mg dry weight, and the α -/~gamma -tocopherol ratio from 0.40 to 0.75. Tocopherol content decreased by 18% but α -/~gamma -tocopherol ratio increased by 44% in roasted seeds. The results indicate that the level of tocopherol in Korean peanut varieties is moderate and the ratio of α - to ~gamma -tocopherol is low.