[Isolation and Identification of Bacteria and Mycete from Preservation of Morinda officinalis].

OBJECTIVE: In order to select antistaling agent which had obvious antibacterial effect on Morinda officinalis, the colony counts of microorganism from the surface of Morinda officinalis and the species of bacteria and mycete were analyzed. METHODS: Bacteria and moulds classification identification method were carried out. RESULTS: After using 10 g burdock oligosaccharide, 20 g chitosan and 0. 5 g potassium sorbate treated for 60 d, the total bacteria on the surface of Morinda officinalis was 3. 0 x 10(4) cfu/g, mycete total of 1. 5 x 10(4) cfu/g, preservation effect was better than the other treatments. CONCLUSION: The common advantage microorganisms group of Morinda officinalis on the surface are from Leuconostoc ,Aerococcus and Penicillium genera.

[Leaf redundancy of high-yielding maize (Zea may L.) and its effects on maize yield and photosynthesis].

According to the maize yield at plant density of 15000 ind x hm(-2) in 2007, the leaf-redundant type (cultivar Chaoshi 1) and non-redundant type (cultivar Chaoshi 3) at low plant density were selected, and the changes of their above-ground dry matter accumulation and grain yield after cutting all leaves to 1/2 (T1) and 1/4 (T2) at anthesis at the optimal density and under high-yielding condition were analyzed in 2008, aimed to approach whether the leaf redundancy exists in high-yielding maize colonies. The characters of grain-filling were simulated by Richards' model, and the photosynthetic characteristics and chlorophyll fluorescence of the leaves on ear position were determined to reveal the activities of photosynthesis after the removal of redundancy. The results showed that at optimal plant density and under high-yielding condition, both the redundant and non-redundant types had leaf redundancy. The characterization of grain-filling by Richards' model indicated that appropriately removing redundant leaves could increase the net photosynthetic rate and solar energy use efficiency of the leaves on ear position, extend the active period of grain-filling, and enhance the grain yield.

[Effects of drought stress on the grain yield and root physiological traits of maize varieties with different drought tolerance].

A pot experiment was conducted to study the effects of simulated moderate drought in whole growth period on the grain yield and root physiological traits of drought-tolerant maize variety JK-628 and drought-sensitive maize variety ND-95. Compared with the control, the grain yield of JK-628 and ND-95 under the stress of moderate drought was decreased by 33.7% and 62.3%, respectively. Under drought stress, the root biomass of the two varieties decreased, with the maximum value appeared ahead. The root/shoot ratio of JK-628 increased at early growth stage but decreased at late growth stage, while that of ND-95 increased all along. ND-95 had a larger decrement of root activity than JK-628. The root SOD activity in drought-stress plants was higher in prophase but lower in anaphase, compared with that in the control, and the time of SOD activity begun to lower was later for JK-628 than for ND-95. The root MDA content in drought-stress plants was increased, and the increment was much higher for ND-95 than for JK-628. In addition, the root soluble protein content in drought-stress plants was decreased, and ND-95 had a larger decrement than JK-628. In a word, under drought stress, the root activity, SOD activity, and soluble protein content of JK-628 were higher than those of ND-95, which could slow down the root aging process and prolong the root functional period, possibly being one of the important factors of getting high yield of drought-tolerant maize under drought stress.

[Effects of controlled-release fertilizers on summer maize grain yield, field ammonia volatilization, and fertilizer nitrogen use efficiency].

A field experiment with colophony-coated fertilizer (CRF) and sulfur-coated fertilizer (SCF) showed that under the same application rates of N, P and K, applying CRF and SCF increased the summer maize grain yield by 13.15% and 14.15%, respectively, compared to the application of common compound fertilizer CCF. When the applied amount of CRF and SCF was decreased by 25%, the yield increment was 9.69% and 10.04%, respectively; and when the applied amount of CRF and SCF was decreased by 50%, the yield had less difference with that under CCF application. The field ammonia volatilization rate in treatments CRF and SCF increased slowly, with a peak appeared 7 days later than that in treatment CCF, and the total amount of ammonia volatilization in treatments CRF and SCF was ranged from 0.78 kg N x hm(-2) to 4.43 kg N x hm(-2), with a decrement of 51.34%-91.34% compared to that in treatment CCF. The fertilizer nitrogen use efficiency and agronomic nitrogen use efficiency of CRF and SCF were also significantly higher than those of CCF.

[Dynamic changes of soil microbial populations and enzyme activities in super-high yielding summer maize farmland soil].

To reveal the characteristics of the dynamic changes of soil microbial populations and enzyme activities in super-high yielding ( > 15,000 kg x hm(-2)) summer maize farmland soil, a comparative study was conducted in the experimental fields in National Maize Engineering Research Center (Shandong). On the fields with an annual yield of >15,000 kg x hm(-2) in continuous three years, a plot with the yield of 20 322 kg x hm(-2) (HF) was chosen to make comparison with the conventional farmland (CF) whose maize yield was 8920. 1 kg x hm(-2). The numbers of bacteria, fungi, and actinomycetes as well as the activities of urease and invertase in 0-20 cm soil layer were determined. The results showed that in the growth period of maize, the numbers of bacteria, fungi, and actinomycetes in the two farmland soils increased first and declined then. At the later growth stages of maize, the numbers of soil microbes, especially those of bacteria and actinomycetes, were lower in HF than those in CF. At harvest stage, the ratio of the number of soil bacteria to fungi (B/ F) in HF was 2.03 times higher than that at sowing stage, and 3.02 times higher than that in CF. The B/F in CF had less difference at harvest and sowing stages. The soil urease activity in HF was significantly lower than that in CF at jointing stage, and the invertase activity in HF decreased rapidly after blooming stage, being significantly lower than that in CF.

[Soil nutrient leaching patterns in maize field under different fertilizations: an in situ study].

An in situ field experiment with lysimeter was conducted to study the effects of different fertilizations on the nutrient leaching loss from brown soil in the growth season of summer maize. The results showed that abundant rainfall and irrigation were the main factors affecting the leaching loss. The leaching amount was higher in the early growth period of summer maize, but decreased after then. The difference among different fertilization treatments also decreased with maize growth. Comparing with N fertilization, wheat stalk plus N application intensified the leaching. During the growth period of summer maize, the NO3- -N content in leached water in fertilization treatments had two peaks, while the NH4+ -N content had a trend of increased first and decreased then. The leaching loss of soil N was mainly in the form of NO3- -N. The accumulative leaching loss of NO3- -N was 12.90-46.53 kg * hm(-2), and that of NH4+ -N was 1.66-5.11 kg x hm(-2), both of which increased with increasing N application rate. The leaching rate of soil N was 6.53%-13.07% higher in treatment wheat stalk plus N application than in treatments of N fertilization, and 3.66%-10.10% higher in low N treatments than in high N treatments. The accumulative leaching loss of available P was only 0.148-0.235 kg x hm(-2), while that of available K was 7.08-13.00 kg x hm(-2). In the late growth period of summer maize, wheat stalk plus N application increased the leaching loss of soil available P and K, while nitrogen application affected it slightly.

[Effects of increasing field temperature on photosynthetic characteristics of summer maize].

A field experiment was conducted to study the effects of increasing field temperature on the grain yield and photosynthetic characteristics of summer maize cultivars ND108 and YD13. The results showed that under increasing field temperature in the period from male tetrad to maturing stage, the grain yield of ND108 and YD13 decreased by 46.6% and 45.1%, leaf area index (LAI) decreased by 15.4% and 11.5%, and net photosynthetic rate of ear leaf decreased by 22.85% and 18.14%, respectively, compared with the control. The contents of leaf chlorophyll a and b, especially that of chlorophyll a, decreased obviously, and the activities of ribulose-1,5-bisphosphate carboxylase (PEPCase) and phosphoenolpyrovate carboxylase (RuBPCase) in the leaves of the two cultivars decreased by 51.1% and 32.4%, and 29.5% and 7.7%, respectively.

[Spatiotemporal variation of root systems of cytoplasmic male sterile maize (Zea may L.) and its homotype fertile lines].

Maize cytoplasmic male sterile (CMS) lines and their homotype fertile lines were cultivated on soil column to study the differences of their root traits at different growth stages after anthesis. The results indicated that CMS lines had stronger ability of dry matter accumulation in their aboveground part, their grain yield was significantly higher than that of homotype fertile lines (P < 0.05), and their root dry mass was higher. In addition, the ratio of their root to canopy had a similar variation trend as root dry mass. The root mass of CMS lines in 0-20 cm and 20-40 cm soil layers was higher than that of homotype fertile lines, and the superiority was more obvious in 40-80 cm soil layer. Compared with homotype fertile lines, CMS lines had significantly higher root activity in 0-20 cm and 20-40 cm soil layers (P < 0.05), and significantly higher root SOD activity and soluble protein content (P < 0.05) in 40-80 cm soil layer. The root activity and root SOD activity and soluble protein content of CMS lines were significantly higher than those of their homotype fertile lines (P < 0.05) at late growth stage. In conclusion, CMS lines had the characteristics of larger root quantity in deeper soil layers and higher root physiological activity at late growth stage, which could prolong the functional period of root and postpone the process of senescence, possibly being one of the important reasons of the high grain yield of CMS lines.

[Effects of high field temperature on summer maize grain yield and quality].

A field study with two summer maize cultivars ND108 and YD13 showed that increased field temperature (3 degrees C) at the stage from male tetrad to maturity had significant effects on their grain yield and quality. The grain yield of ND108 and YD13 decreased by 46.6% and 45.1%, grain crude protein content increased by 11.6% and 2.02%, ether extract content decreased by 38.9% and 9.6%, starch (mainly amylopection) content decreased by 7.0% and 8.4%, and lysine content decreased by 58.9% and 51.2%, respectively.

[Effects of weak light stress on grain yield and photosynthetic traits of maize].

Through shading at 0-14 days before pollination (S1), 1-14 days after pollination (S2), and 15-28 days after (S3) pollination, this paper studied the effects of weak light stress on the grain yield and photosynthetic traits of maize cultivars FY3 and TY2. The results showed that all treatments of shading induced a decreased grain yield, among which, treatment S1 had the largest decrement, and FY3 was more sensitive to the shading. Weak light stress made the time of maximum grain-filling (Tmax) appeared later, grain-filling slowed down, and mass accumulation decreased. The earlier the weak light stress occurred, the later the Tmax appeared. During shading, the Chl (a + b) content, Chl a/b ratio, photosynthetic rate (Pn) as well as the photochemical efficiency (Fv/Fm) and actual quantum yield of PS II electron transport (phi(PS II)) in maize leaves decreased significantly, while the relative content of Chl b increased, and the intercellular CO2 concentration (Ci) and non-photochemical quenching (NPQ) increased markedly. After the shading ended, the Chl (a + b) content, Chi a/b ratio, Pn, Fv/Fm, phi (PS II), Ci, and NPQ restored gradually to the levels of non-shading, but the relative content of Chl b decreased, which suggested that non-stomatal limitation was part of the reason for the decreased Pn under weak light stress.