Classification of Azolla spp., section Azolla

Summary Azolla accessions (section Azolla) from the germplasm collections of the International Rice Research Institute and Washington State University were fingerprinted and classified by enzyme electrophoresis and leaf trichome morphology. A. filiculoides was enzymatically distinctive and also reliably identified by its prominent one-celled trichomes. Neotropical accessions labelled as A. filiculoides proved to be members of other species. Two groups of isolates were designated A. rubra, but those from Japan were identified as A. filiculoides. The A. rubra of Australia-New Zealand was biochemically unique and possessed less protuberant trichomes than A. filiculoides. A. microphylla, A. mexicana, and A. caroliniana were phenetically similar, but a. microphylla was identifiable from the others in the banding patterns of certain enzymes. A. mexicana and A. caroliniana were closely related enzymatically. The two-celled leaf trichomes of these three species were similar in size and shape.     

The effect of rhizosphere of various plants on the growth of Rhizobium

As elucidated in the previous paper¹⁾, the rhizosphere of the host plant maintains more abundant root nodule bacteria than non-rhizosphere soil. The success of seed inoculation of the root nodule bacteria is supported by the multiplication in the vicinity of the host plant.     

Growth inhibition due to continuous cropping of dryland rice and other crops

Rice, corn, sorghum, mungbeans, and cowpeas were continuously grown on the same land at 2- to 6-week intervals between crops to determine effects on yield. Decline of growth and yield occurred during continuous cropping. Dryland rice, mungbeans, and cowpeas were affected most, corn slightly, and sorghum was not visibly affected.

Growth inhibition in dryland rice and mungbeans occurred after one or two crops; growing the same crop in rapid succession resulted il1low grain yields. The persistence of inhibitory effects was indicated. One crop rotation or 5 months of fallow removed only a part of the harmful effects.

The causal agent appears to have a specific affinity to the host crop. Root residues of the previous crop may serve as a source of the causal agent for the subsequent crop.

Biological agents were involved in growth inhibition of rnungbeans and dryland rice. In mungbeans, the inhibitory effects appeared to be directly dependent on microorganisms. It appeared that microorganisms were not the primary cause of harmful effects in dryland rice.     

Evaluation of N and P mass balance in paddy rice culture along Kahokugata Lake, Japan, to assess potential lake pollution

Kahokugata Lake, a closed lake, has been subject to eutrophication. This research was conducted to clarify the actual phenomena and evaluation of the discharges of N and P from paddy test fields in the lowlands into Kahokugata Lake. A comprehensive mass balance of N and P was obtained from 4 years of study. About N, the mean value of harvested unhulled rice (79.9 kg/ha) was greater than mean controlled release fertilizer inputs (56.7 kg/ha). Other inputs and outputs include N in atmospheric acid deposition (21.4 kg/ha) and N fixation–denitrification (9.2 kg/ha). The rice straw recycled after harvest was balanced by straw produced in the succeeding year. The runoff and percolation losses discharged into the lake was 11.3 kg/ha, (8.6% of total inputs). Since the rice harvested was consumed domestically, which taking out from the farmland and, therefore, nitrogen pollutant into the lake was becoming small, paddy rice at this site is considered an “anti-polluting, purifying or cleansing” crop. The P content in harvested rice (39.4 kg/ha) was balanced by fertilizer inputs (36.4 kg/ha). Previous studies examining inflow–outflow relationships without considering a comprehensive mass balance may lead to erroneous conclusions. Our findings indicate paddy rice in lowlands could be an environmentally friendly crop and can play an important role in reducing pollution of lakes, and therefore should be considered in land use planning.     

Evaluation of technologies for sequestering carbon in agricultural land by using organic filter underdrains

Technology for storing carbon in the subsoil of agricultural land using organic filter materials in underdrains was evaluated as an activity for sequestering CO₂ to mitigate global warming. First, the quantity of carbon remaining in wood chips and rice husks in underdrains was determined over 11 years after construction. Moreover, the quantity of CO₂ emissions from the construction of two underdrain types was calculated. Then, a survey was conducted to investigate the effect on greenhouse gas emissions of the filter material. The results indicate that greenhouse gas emissions would not increase. The quantity of storage carbon in the wood chip filter material of underdrains during their 15-year service life was estimated to be 6.76 tCO₂eq ha^?1. Rice husks, in contrast, were found ineffective in storing carbon. Therefore, the selection of the filter material for underdrains is important. The value of storage carbon in the wood chip filter material is similar to the amount of carbon sequestered by no-till farming, which is now being implemented as a global warming countermeasure based on soil management in agricultural land.     

Analysis of the nitrogen pollution load potential from farmland in the Tedori River Alluvial Fan Areas in Japan

A nitrogen balance study was carried out by setting up a test paddy in order to estimate the nitrogen pollution load potential (NPLP) from farmland in the Tedori River Alluvial Fan Areas and the load from the entire area under consideration was estimated using the cropping record and fertilizer application rate (FAR). The total NPLP was estimated to be 261 tons/year and the load from the paddy 79 tons/year for 5,704 ha, which would translate to an intensity of 14 kg/ha, while the load from the vegetable field was estimated to be 118 tons/year for 215 ha, which would equate to an intensity of 549 kg/ha. The pollution loads for the vegetables were significantly greater than those for the rice. The load for the barley was 57 tons/year for 261 ha (216 kg/ha) and that for the orchards was 23 tons/year for 64 ha (359 kg/ha). The estimation of soybean load was a negative 15 tons/year for 717 ha (−21 kg/ha), which meant that the nitrogen in the yield was greater than the FAR. The results also confirmed the yield absorption ratio in relation to the FAR. The load from the paddy for the entire area was also estimated using the percolation rate and the water quality load underneath the farmland was estimated to be 89 tons/year.     

Drainage and irrigation performance of hybrid ditches in converted paddy fields under winter wheat cultivation in Hokkaido

Paddy fields converted into winter wheat fields in Hokkaido, Japan, receive extremely high snowfall, creating a risk of flood damage to crops in spring due to waterlogging of snowmelt runoff and poor drainage. Meanwhile, in June there is relatively little rainfall, and a lack of moisture inhibits winter wheat growth. Therefore, we developed a method involving a series of 30-cm-deep ditches in agricultural fields to be used for drainage during the flood-prone period and for furrow irrigation during the dry period using water drawn from the canals that feed the paddy fields. The ditches are called ‘hybrid ditches’ as they are able to perform both drainage and irrigation functions. In this study, we investigated the optimal construction timing and spacing for hybrid ditches. We also evaluated their ability to improve the drainage and irrigation of winter wheat. We found that the optimal timing for digging hybrid ditches is immediately after sowing, and the inter-ditch spacing for irrigation should be 15 m or less. The hybrid ditches promoted increased soil temperature and healthy development of wheat plants by improving drainage during the flood-prone period. In addition, water was successfully supplied via the hybrid ditches to irrigate the fields in June. Under experimental conditions in which rainfall was excluded, grain yield was 10% higher and percent protein content was more than 1% point greater in the irrigated plot compared with the non-irrigated plot. Grain yield was also observed to increase by 3–29% in demonstration tests conducted at local farms. From these results, we conclude that hybrid ditches are capable of improving the growth and yield of winter wheat by improving drainage and providing irrigation in converted paddy fields in Hokkaido.     

Evaluation of technologies for sequestering carbon in agricultural land by using organic filter underdrains

Technology for storing carbon in the subsoil of agricultural land using organic filter materials in underdrains was evaluated as an activity for sequestering CO₂ to mitigate global warming. First, the quantity of carbon remaining in wood chips and rice husks in underdrains was determined over 11 years after construction. Moreover, the quantity of CO₂ emissions from the construction of two underdrain types was calculated. Then, a survey was conducted to investigate the effect on greenhouse gas emissions of the filter material. The results indicate that greenhouse gas emissions would not increase. The quantity of storage carbon in the wood chip filter material of underdrains during their 15-year service life was estimated to be 6.76 tCO₂eq ha⁻¹. Rice husks, in contrast, were found ineffective in storing carbon. Therefore, the selection of the filter material for underdrains is important. The value of storage carbon in the wood chip filter material is similar to the amount of carbon sequestered by no-till farming, which is now being implemented as a global warming countermeasure based on soil management in agricultural land.

     

几种坡度的台阶式溢洪道消能特性试验研究

对3种斜坡(5.7°,19°和30°)的台阶式溢洪道进行了模型试验研究。结果表明,当堰上相对临界水深yc/h≤2.5时,滑行水流、过渡水流和跌落水流消能率的大小不受堰上相对临界水深的限制,而只是相对坝高Hdam/yc和斜坡角度的函数,即随坡度变缓或相对坝高Hdam/yc增加,消能率增大;当坝坡相同坝高相等时,滑行水流、过渡水流和跌落水流之间的消能率差异很小,并且其消能率大小与台阶个数无关;此外,文中还给出了计算消能率的经验公式。     

Anticancer Alkaloid Lamellarins Inhibit Protein Kinases

Lamellarins, a family of hexacyclic pyrrole alkaloids originally isolated from marine invertebrates, display promising anti-tumor activity. They induce apoptotic cell death through multi-target mechanisms, including inhibition of topoisomerase I, interaction with DNA and direct effects on mitochondria. We here report that lamellarins inhibit several protein kinases relevant to cancer such as cyclin-dependent kinases, dual-specificity tyrosine phosphorylation activated kinase 1A, casein kinase 1, glycogen synthase kinase-3 and PIM-1. A good correlation is observed between the effects of lamellarins on protein kinases and their action on cell death, suggesting that inhibition of specific kinases may contribute to the cytotoxicity of lamellarins. Structure/activity relationship suggests several paths for the optimization of lamellarins as kinase inhibitors.