Short-term evaluation of oxygen transfer from rice (Oryza sativa) to mixed planted drought-adapted upland crops under hydroponic culture

Mixed cropping is a cultivation method widely practiced in tropical regions. The newly developed close mixed planting technique mitigates the flood stress of drought-adapted upland cereal species by co-growing rice (Oryza sativa) plants under field flood conditions. We tested the hypothesis that O₂ was transferred from rice to upland crops using the model system of hydroponic culture. To confirm the hypothesis, the phenomena of O₂ absorption and release by plants were evaluated in a water culture condition without soil. Experiments were conducted in a climate chamber to estimate the amount of O₂ released from the roots of rice and pearl millet (Pennisetum glaucum) under both O₂-rich (20.0 ± .0% conc. in phase I) and O₂-free dark (.8 ± .0% conc. in phase II) conditions. The total O₂ change (between the two phases) in a single planting of rice and pearl millet was significantly higher than that of the mixed planting of rice and pearl millet, which indicated that O₂ was transferred from rice to pearl millet under a water culture condition. The result indicated that approximately 7 μM O₂ g fresh root weight^?1 h^?1 was transferred between the two plant species. O₂ transfer was confirmed between the two plant species in a mix cultured in water, implying its contribution to the phenomenon that improved the physiological status of drought-adapted upland crops under field flood conditions.     

Primary aminophospholipids in the external layer of liposomes protect their component polyunsaturated fatty acids from 2,2'-azobis(2-amidinopropane)- dihydrochloride-mediated lipid peroxidation

We showed in our previous study that docosahexaenoic acid-rich phosphatidylethanolamine in the external layer of small-size liposomes, as a model for biomembranes, protected its docosahexaenoic acid from 2,2'-azobis(2-amidinopropane)dihydrochloride- (AAPH-) mediated lipid peroxidation in vitro. Besides phosphatidylethanolamine, both phosphatidylserine and an alkenyl-acyl analogue of phosphatidylethanolamine, phosphatidylethanolamine plasmalogen, are reported to possess characteristic antioxidant activities. However, there are few reports about the relationship between the protective activity of phosphatidylethanolamine plasmalogen and/or phosphatidylserine against lipid peroxidation and their distribution in a phospholipid bilayer. Furthermore, it is unclear whether phosphatidylethanolamine plasmalogen and/or phosphatidylserine protect their component polyunsaturated fatty acids (PUFAs) from lipid peroxidation. In the present study, we examined the relationship between the transbilayer distribution of aminophospholipids, such as phosphatidylethanolamine rich in arachidonic acid, phosphatidylethanolamine plasmalogen, and phosphatidylserine, and the oxidative stability of their component PUFAs. The transbilayer distribution of these aminophospholipids in liposomes was modulated by coexisting phosphatidylcholine bearing two types of acyl chain: dipalmitoyl or dioleoyl. The amounts of these primary aminophospholipids in the external layer became significantly higher in liposomes containing dioleoylphosphatidylcholine than in those containing dipalmitoylphosphatidylcholine. Phosphatidylethanolamine rich in arachidonic acid, phosphatidylethanolamine plasmalogen or phosphatidylserine in the external layer of liposomes, as well as external docosahexaenoic acid-rich phosphatidylethanolamine, were able to protect their component PUFAs from AAPH-mediated lipid peroxidation.     

EPIZOOTIOLOGIC STUDY OF MID-CYCLE DISEASE OF LARVAL Macrobrachium rosenbergii

Mid-cycle disease (MCD) of larval Macrobrachium rosenbergii has reduced survival of larval cultures at the state facility from a normal 50–70% of the population at the post-larval stage, to 5–10%. Observations revealed a characteristic mortality pattern, where a peak in daily mortality occurred near the middle of the rearing cycle. Epizootiologic studies were initiated using existing facilities, to aid in characterization of MCD and elucidate possible causes. Experiments were undertaken in duplicate culture tanks, each separated into 4 equal volume compartments by nitex screen. Water, algae, and some feed could pass between compartments; prawn larvae could not. “Reference” larvae were introduced into a compartment of each tank on the day of hatch. “Test” larvae populations of different ages and sources were introduced into the remaining compartments at various times after the initiation of the experiment. Dead larvae in the bottom sediment were counted daily and mortality curves generated. Length and developmental stage of live and dead animals in each compartment were assessed daily. Results indicated that a “toxic period” of unknown etiology began on the 10th day of culture and probably extended for the duration of the rearing cycle. “Test” populations introduced during the “toxic period” displayed a mortality peak within 4–6 days. Larvae at age 15 days (stage 6–7) or older appeared refractory to the “toxicity.” MCD apparently reduced growth rates (length) but did not appear to selectively kill larger, faster growing, susceptible individuals. Problematically large portions of animals lost from populations were not accounted for. Studies on MCD will continue.     

Blood parameters and electrocardiogram in squeezed fish simulating the effect of net damage and recovery

ABSTRACT:   In the present study, rubber bands were tied around the girth of rainbow trout Oncorhynchus mykiss to simulate and assess the physiological damage and survival rates of fish that encounter gill nets. Physiological condition was assessed by analysis of blood lactate, pH, oxygen partial pressure and plasma potassium concentration before and after release from binding. Twenty-four hours after release, half of the test fish had died. Although the binding forces used to hamper fish did not differ significantly, blood lactate levels in the dead fish rose to 10-fold higher than those in the survivors. Consequently, the pH level fell in the group that died, whereas in the surviving group it fell only slightly and soon recovered. Potassium concentration increased after release from binding in fish that died, and the P o ₂ levels in these fish continued to drop until just before death. It was concluded that when fish get entangled in fishing nets, blood lactate accumulates because of physical fatigue and the elevated lactate levels lead to metabolic acidosis. Finally, fatal metabolic conditions could cause higher mortality rates, even in escapees.     

Root pruning is effective in alleviating the inhibition of soybean growth caused by anaerobic stress for a short period

Soybean is an important upland crop,but its productivity is often limited by anaerobic stress caused by waterlogging.The ability to adjust root growth under environmental constraints is an important physiological trait for adapting to an everchanging environment,and root pruning is an artificial technique for regenerating the root system.In the present study,we investigated whether root pruning in soybean can effectively alleviate the inhibitory effects of anaerobic stress.Soybean plants were af...     

Soil chemical properties of an Indonesian red acid soil as affected by land use and crop management

In the middle terrace area of south Sumatra, Indonesia, where red acid soils poor in crop productivity are widely distributed, the effects of cropping pattern and cultivation techniques on physico-chemical properties of soil were investigated. Five patterns for cassava cropping, including monoculture, a rotation with annual food crops, and three intercroppings with differences in the combination with annual crops and in the planting density, were evaluated in Experiment I. In Experiment II, eight plots composed of the combinations of two tillage methods (no-tillage or conventional tillage), the presence or absence of surface mulch from crop residues, and two rates of chemical fertilizers were established for a maize–soybean–cowpea sequential cropping pattern. At the end of 3 years, there was no difference in total C and total N concentrations among the plots in Experiment I irrespective of the mulch treatment using crop residues. Soil organic matter (SOM) concentration was not affected even in the no-tillage plot where the maximum crop residues (20 t ha⁻¹) was given as surface mulch with the increased root residues due to higher rates of fertilizers (Experiment II). In Experiment I, available P concentration was highest in an intercropping with higher fertilizer rates and lowest cassava planting density. In Experiment II, an increase in available P was attained by mulching and the higher rate of fertilizers, and a minor positive effect of fertilizer was also observed in exchangeable Mg and K concentrations. Surface mulch resulted in less clay fraction compared with the non-mulch plots in both the experiments, suggesting its effect on the maintenance of soil particle distribution. An additional finding suggested no prominent influence of cassava monoculture on the level of SOM in this area based on the comparison with other major land uses, including secondary forest, rubber plantation, and mixed cultivation of fruits with crops. Nevertheless, the introduction of crop residue mulch and higher rates of fertilizers are recommended for sustaining soil quality and achieving higher crop yields.