Effects of temperature and organic and inorganic nutrients on the growth of Chattonella marina (Raphidophyceae)from the Daya Bay,South China Sea

The effects of temperature and different forms of nutrients on Chattonella marina growth have been investigated in strains isolated from the Daya Bay, the South China Sea. The strain of C. marina preferred high temperatures, with an optimal temperature of 25℃, and 18℃ was the minimum for its survival. Higher cell number and growth rate were obtained in high nitrogen and phosphorus concentrations （500 μg/L, 74μg/L） than under nutrient limitation. Nitrogen influenced the growth most, as the specific growth rate and maximum cell density were lower in nitrogen- limited cultures than noted under phosphorus limitation or under limitation from both. C. marina was capable of using many kinds of organic nitrogen sources including L-serine （L-Ser）, glycine （Gly）, alanine （Ala）, L-threonine （L-Thr）, glutamic acid （Glu） and urea, but could not utilize uric acid. Various forms of organic phosphorus compound such as glucose-6-phosphate （G6P）, sodium glycerophosphate （GYP）, adenosine triphosphate （ATP）, adenosine monophosphate （AMP）, cyti- dine monophosphate （CMP）, guanosine monophosphate （GMP）, uridine monophosphate （UMP）, 4-nitrophenylphosphate （NPP） and triethyl phosphate （TEP） supported the growth as well. Algal cells had the ability to sustain growth under nitrogenand/or phosphorus-free conditions particularly under phosphorus depleted condition. These results led to the hypothesis that high loading of nitrogen has played an important role in frequent C. marina blooms in the past decade, and its capability for utilization of diverse forms of organic nutrients and growth in low nutrient conditions make this species a likely recurrent dominant in the Daya Bay phytoplankton assemblages, visible as more frequent blooms.

Soil microbial biomass and its controls

Microbial biomass represents a relatively small standing stock of nutrients, compared to soil organic matter, but it can act as a labile source of nutrients for plants, a pathway for incorporation of organic matter into the soil, and a temporary sink for nutrients. This review describes several factors controlling the dynamics of soil microbial biomass. These factors mainly include organic carbon and nitrogen limitation, residue and nutrient management, differences in plant species, soil texture, soil moisture and temperature. On the basis of detailed analysis, it is reasonable that future research would be focused on the impact of land use change on soil MB in tropical and subtropical ecosystems.

In vitro propagation of the endangered medicinal orchid,Dendrobium lasianthera J.J.Sm through mature seed culture

Objective:To study asymbiotic seed germination and mass propagation of Dendrobium lasianthera which is one of the endangered medicinal orchids using seeds.Methods:The 14 weeks old hand pollinated seeds were sown on Vacin and Went(VW)solid medium supplemented with various concentrations of peptone(1,2,3 g/L) and without peptone which was used as control treatment.At the 4,8,and 12 weeks after the seeds were sown,seed germination and shoot formation were investigated.To evaluate the role of organic nutrient additives on subsequent shoot development and root formation,particular shoots with about 1 cm length contains 1–2 leaves obtained from the seeds germination was cultured on VW medium additives with different of organic nutrient:15% coconut water,2 g/L peptone,150 g/L banana homogenate,and without organic nutrient was used as control.After 16 weeks of culture,the plantlet height,number of leaves,number of roots,leaf length and root length were recorded.Results:The supplementation of 2 g/L peptone in VW medium was proven to be suitable concentration for seed germination(100%) and shoot formation with 84.0% the protocorm development to phase 5(shoot).VW medium containing 15% coconut water was effectively improved the shoot development,with well developed roots and leaves compared to the other treatment and 95% of acclimatized plantlets survived.Conclusions:This protocol is an efficient way for the in vitro mass propagation of this Dendrobium lasianthera.

Effect of water regimes and organic matters on transport of arsenic in summer rice (Oryza sativa L.)

The arsenic contamination in soil-water-plant systems is a major concern of where, the groundwater is being contaminated with arsenic （above 0.01 mg/L） in the Indian subcontinent. The study was conducted with organic matter to find out the reducing effect on arsenic load to rice （cv. Khitish）. It was observed that intermittent ponding reduced arsenic uptake （23.33% in root, 13.84% in shoot and 19.84% in leaf） at panicle initiation stage, instead of continuous ponding. A decreasing trend of arsenic accumulation （root straw husk whole grain milled grain） was observed in different plant parts at harvest. Combined applications of lathyrus ＋ vermicompost ＋ poultry manure reduced arsenic transport in plant parts （root, straw, husk, whole grains and milled grain） which was significantly at par （p 0.05） with chopped rice straw （5 tons/ha ） ＋ lathyrus green manuring （5 tons/ha） in comparison to control and corresponding soils. A significant negative correlation of arsenic with phosphorus （grain P with arsenic in different parts R 2 = 0.627–0.726 at p 0.01） was observed. Similarly, soil arsenic had a negative correlation with soil available phosphorus （R 2 = 0.822 at p 0.001） followed by soil nitrogen （R 2 = 0.762 at p 0.01） and soil potassium （R 2 = 0.626 at p 0.01）. Hence, effective management of contaminated irrigation water along with organic matter could reduce the arsenic build up to plants and soil.