Changes in the potato (Solanum tuberosum L.) tuber at the onset of dormancy and during storage at 23°C and 3°C. I. Biochemical and physiological parameters

Summary In the last 30 d of potato (Solanum tuberosum L.) tuber growth metabolic activity decreased. Levels of glucose-6-P and sucrose in whole tuber tissues declined and in tuber slices there was a decrease in the uptake from the medium and in the incorporation into macromolecules of [U-¹⁴C]sucrose. During storage at 23°C only the uptake of [U-¹⁴C]sucrose increased concomitant with tuber sprouting, indicating a possible involvement of the transport mechanisms in dormancy breaking. At 3°C, levels of reducing sugars and sucrose increased in response to the low temperature and increased release of K⁺ and malondialdehyde levels indicated cell membrane damage. The cell membrane functionality was restored at sprouting. The sprouting potential of the tubers was evaluated using the sprouting ability of single-bud explants (“seedcores”) in response to water, GA₃ or ABA dips. This sprouting potential of tubers changed with stage of tuber growth and storage duration and temperature, indicating that the tissue hormonal state changed strongly throughout tuber life, probably in relation with the “sink” to “source” transition.     

Effects of Free-air CO2 Enrichment on Root Characteristics and C：N Ratio of Rice at the Heading Stage

The CO2 concentration in Earth’s atmosphere is increasing rapidly due to human activities, like fossil fuel combustion and rapid deforestation and is predicted to reach a concentration of 550 μmol/mol within this century [1]. The increase in atmospheric CO2 has a large potential to alter many ecosystem processes, particularly C and N cycling [2-4]. Plant C:N ratio not only serves as an important factor in maintaining the quality of plant tissue, but also a key index to keep balance betwee…     

Field assessment of imidacloprid to reduce the spread of PVY° and PLRV in potato

A three year field study conducted at the Potato Research Centre in Fredericton, New Brunswick, showed that imidacloprid applied in furrow at planting or twice to the foliage in mid July could result in a limited reduction of PLRV spread in the potato crop. Tests did not determine any significant effect on the reduction of the spread of PVY. The aphicidal property of imidacloprid was confirmed.     

Characterization of Pseudomonas spp.and related bacteria from rice seeds in the subtropics and the tropics

To explore the bacterial diversity for sustain-able management of the major rice diseases,asurvey of bacterial diversity of rice seed wasconducted in Luzon Island of the Philippines(the tropics)and in Zhejiang Province of China(the subtropics),during 1993-1998.One hun-dred sixteen(0.5kg/sample)and 129(1kg/sample)seed samples were collected from the subtropics and the tropics,respectively.Morethan 3000 bacterial isolates were picked and examined under the UV light for their fluores-cence.After colony morphological,pathogeni-cal,and some bacteriological tests,816 non-pathogenic bacteria isolates were selected forfurther identification using a numeric taxono-     

Investigation on the cold tolerance of Dongxiang wild rice at seedling and heading stage

Dongxiang wild rice is an ecological type ofwild rice that grows at 28°14′N. To study itscold tolerance, Dongxiang wild rice (Shang-tang 3) was compared with three cold tolerantlate season rice varieties, i. e. M112, IR24(in-dica), and Jing0298 (japonica), and three coldsensitive indica varieties, i. e. 754, 6226, and     

Germination of Wheat Grains at Various Temperatures in Relation to the Activities of α-Amylase and Endoprotease

Abstract

Germination percentages of wheat grains sampled at 3 grain-filling stages : yellow-ripe stage (water content 45-50%), dough-ripe stage (35-40%), and full-ripe stage (25-30%), and imbibed in water at 12°C and 20°C were examined in relation to the activities of α-amylase and endoprotease. Wheat varieties studied were Chihoku-komugi, which is susceptible to pre-harvest sprouting, and Satanta, which is resistant. Germination percentage was higher at 12°C than at 20°C in all grains sampled at all stages in both varieties, and was higher in Chihoku-komugi than in Satanta at 20°C. The activity of α-amylase in the grains at the yellow-ripe stage was higher at 12°C than at 20°C in both varieties, but that at the other 2 stages was higher only in Satanta. Endoprotease increased rapidly from 7 to 10 days after the start of imbibition, and exceeded 12 units only at 12°C in Chihoku-komugi grains at the dough and full-ripe stages. The results showed that α-amylase activity was lower than the value equivalent to 300 brabender unit (BU) in amylography when the germination percentage was 0%. Endoprotease activity exceeded 6 units when the germination percentage exceeded 90%.     

Neuroprotective Effects of the Cultivated Chondrus crispus in a C. elegans Model of Parkinson’s Disease

Parkinson’s disease (PD) is the second most common neurodegenerative disorder in the elderly people, currently with no cure. Its mechanisms are not well understood, thus studies targeting cause-directed therapy or prevention are needed. This study uses the transgenic Caenorhabditis elegans PD model. We demonstrated that dietary supplementation of the worms with an extract from the cultivated red seaweed Chondrus crispus decreased the accumulation of α-synulein and protected the worms from the neuronal toxin-, 6-OHDA, induced dopaminergic neurodegeneration. These effects were associated with a corrected slowness of movement. We also showed that the enhancement of oxidative stress tolerance and an up-regulation of the stress response genes, sod-3 and skn-1, may have served as the molecular mechanism for the C. crispus-extract-mediated protection against PD pathology. Altogether, apart from its potential as a functional food, the tested red seaweed, C. crispus, might find promising pharmaceutical applications for the development of potential novel anti-neurodegenerative drugs for humans.     

Derivatives of Salarin A,Salarin C and Tulearin A—Fascaplysinopsis sp. Metabolites

Derivatives of salarin A, salarin C and tulearin A, three new cytotoxic sponge derived nitrogenous macrolides, were prepared and bio-evaluated as inhibitors of K562 leukemia cells. Interesting preliminary SAR (structure activity relationship) information was obtained from the products. The most sensitive functionalities were the 16,17-vinyl epoxide in both salarins, the triacylamino group in salarin A and the oxazole in salarin C (less sensitive). Regioselectivity of reactions was also found for tulearin A.     

The impacts of timing and insecticides at early stage of late rice on the population development of brown plant hopper （BPH）

Field experiments were carried out in northern Zhejiang Province. Three insecticides (methamidophos,Shachongshuang and triazophos) were used to control the rice leaffolder Cnaphalocrocis medinalis and rice striped stemborer Chilo suppressalis in rice fields during 18—27 days after transplantating. The impacts of timing and insecticides on the population development of brown planthopper Nilaparavata lugens was surveyed by direct counting on the plants or by tapping method.     

Biological characteristics of Ustilaginoidae virens and the screening in vitro of the causal pathogen of false smut of rice and fungicides

Green smut bails were collected from diseased rice panicles and surtace sterilized in sodium chloride for 5 minutes. The orange colored internal tissues were placed on PDA medium kept at 25℃ for 5 d to get pure cultures. PDA plates with the pathogen mycelial pieces in diameter of 5mm were incubated under 9 temperature grades ranged from 13 to 35℃.     

Effect of different factors on the induced resistance of Xanthomonas oryzae pv. oryzae and relationship between the effect and active oxygen metabolism in rice seedling leaves

We studied the relationship between the resistance to Xanthomonas oryzae pv, oryzae (XOO) and active oxygen species (AOS).Materials used were Yushuinuo (high resistant) and Zhefu 802 (high susceptible).Paraquat (PQ) specially generated superoxide anion (O2 ) and Tiron (4, 5-dihydroxy-1.3-benzenedisufonic acid).     

Preliminary studies on radiant spectrum of the leaves of the paddy and upland rice

To study the property of the radiant spectrum(RS),i.e.absorption,reflectance and trans-mission ratio.Four upland rice varieties i.e.Haogelao,Hongkuo—laoshuya,Chengjiang—ludao,and IRAT—109,and four paddy ricevarieties Xifeng,Akihikari,Zhongbai 4,andYuefu were sown at Beijing on dry land in themiddle May,1992 and 1993.The plants weretreated with drought stress during seedling,booting,heading and flowering stages.It wasrainy season or intermittent irrigation duringother period.The RS and the chlorophyll con-tent of the third leave of seedlings and that offlag leave at heading—flowering period weremeasured with UV—190 model spectrometer.The results are shown in Fig 1 and Fig 2.There were little difference of RS in 800-200 mn and chlorophyll content between theleaves of paddy and upland rice during seedlingstage (Fig 1).However,remarkable differ-     

Polyunsaturated Aldehydes from Large Phytoplankton of the Atlantic Ocean Surface (42°N to 33°S)

Polyunsaturated aldehydes (PUAs) are organic compounds mainly produced by diatoms, after cell wounding. These compounds are increasingly reported as teratogenic for species of grazers and deleterious for phytoplanktonic species, but there is still scarce information regarding concentration ranges and the composition of PUAs in the open ocean. In this study, we analyzed the spatial distribution and the type of aldehydes produced by the large-sized (>10 μm) phytoplankton in the Atlantic Ocean surface. Analyses were conducted on PUAs released after mechanical disruption of the phytoplankton cells, referred to here as potential PUAs (pPUAs). Results show the ubiquitous presence of pPUA in the open ocean, including upwelling areas, as well as oligotrophic gyres. Total pPUA concentrations ranged from zero to 4.18 pmol from cells in 1 L. Identified PUAs were heptadienal, octadienal and decadienal, with heptadienal being the most common (79% of total stations). PUA amount and composition across the Atlantic Ocean was mainly related to the nitrogen:phosphorus ratio, suggesting nutrient-driven mechanisms of PUA production. Extending the range of trophic conditions considered by adding data reported for productive coastal waters, we found a pattern of PUA variation in relation to trophic status.     

lsozyme analysis on progenes of somatic hybrids of Oryza sativa L.and O.officinalis

Some wild species of Oryza possess agronomically useful traits such as disease/insect resis tance and salt tolerance. However, the use of wild Oryza species for rice improvement has been hampered by the sexual incompatibility or sterility of hybrids obtained by conventional methods. We have used protoplast fusion as a method to incorporate useful trait of wild O ryza species into cultivated rice and obtained somatic hybrid plants between O.satlva and O.officinalis and their progenies. Isozyme analysis is a method to confirm somatic hybrids and to determine the nuclear constitution of somatic hybrids. The esterase and peroxidase isozyme analysis in progenies of somatic hybrids were herein reported. Two breeding lines PF52 and PF79 were F_2 lines developed form somatic hybrids of O.sativa L.cv. 02428 and O.officinalis accesion. O.sativa L.cv. 02428 and O.officinalis were used as control. Fresh leaves from plants growing in greenhouse were homogenized with extraction