Biomedical subjects

Weixing Cao

Publications and source records attributed to Weixing Cao.

At least 19 recordsLinked to original sources

PubMed2006

[Quantitative relationships between leaf area index and canopy reflectance spectra of wheat].

Based on the change patterns of leaf area index (LAI) and canopy spectral reflectance of wheat at different growth stages and nitrogen application rates, this paper investigated the relationships of LAI with canopy reflectance and spectral parameters, and brought forward the sensitive spectral parameters and quantitative equation for predicting wheat LAI. The results showed that with increasing nitrogen application rate, wheat LAI and its canopy reflectance at near infrared (760 to approximately 1220 nm) increased, whereas the reflectance at visible band (460 to approximately 710 nm) decreased. From jointing to maturity, the LAI and the reflectance of short bands in near infrared increased initially and decreased then, whereas the reflectance of visible light and long bands in near infrared was in adverse, with the lowest value appeared at booting stage. Wheat LAI was negatively correlated with the reflectance of visible light, but positively with that of short bands in near infrared, with the highest correlation coefficient at 810 nm. It was proposed that wheat LAI could be well monitored by vegetation indices RVI (810, 510) and DVI (810, 560). PVI and TSAVI were proved to be the spectral indices in monitoring wheat LAI, and higher accuracy was obtained with combined RVI (810, 510), DVI (810, 560) and PVI.

Ecosystem↗

PubMed2005

[An ecological model for predicting amylose content in rice grain].

By planting rice varieties Indica and Japonica under different ecological environments in China, Japan and Thailand, this study analyzed the relationships between the grain amylose content of test varieties and the environmental factors including latitude, altitude, temperature and solar radiation during grain filling period, established the factor-driven equations for amylose accumulation in rice grain, and developed an ecological model for predicting rice grain amylose content. The model was validated by using the data of different years, sites and varieties, with the RMSE being 0.4% and 0.5% for the grain amylose content of Indica and Japonica, and 0.39% and 0.50% for their planting areas, respectively. The results indicated that the model was accurate and applicable.

Amylose↗

PubMed2005

[Yield-formation and source-sink characteristics of rice genotypes under two different eco-environments].

With nine Japanese varieties and two local cultivars of rice as test materials, this paper studied the characteristics of their yield-formation and source-sink characteristics under different eco-environments of Nanjing and Lijiang. The results showed that eco-environment had an obvious effect on rice grain yield and dry matter accumulation. High-yielding rice genotypes could accumulate more dry matter, especially in their late growth period. They had higher total spikelet number, leaf area index (LAI) and crop growth rate (CGR), as compared with other genotypes. The grain yield increased with increasing total dry matter accumulation, and significantly positively correlated with dry matter accumulation after heading, total spikelet number, LAI, and spikelet/leaf area ratio. The results suggested that the lower grain yield in Nanjing than in Lijiang was mainly resulted from the lower LAI, total spikelet, dry matter accumulation and CGR after heading.

Biomass↗

PubMed2005

[A physiological development time-based simulation model for cotton development stages and square- and boll formation].

In this study, three cotton varieties (CRI 36, CRI 35 and CRI 41) were planted in Nanjing, Anyang, Baoding and Shihezi, respectively, in 2002, and the dynamic relationships between their development and environmental factors were analyzed. Based on this, a simulation model for cotton development stages and square-and boll development was built in terms of physiological development time (PDT). In calculating relative thermal effectiveness, the effect of diurnal temperature differences in different regions on cotton development was incorporated, and the enhancement of plastic mulching on air temperature was quantified. To simulate development stages, the initial fruiting node index (IFIN), sunlight duration factor (FSH), and solar radiation index on fruiting branch (IFBR) were introduced, besides earliness factor of a given genotype. The validation of the model with the data obtained from different years, ecological zones, genotypes, and cultivation practices indicated a high goodness of fitness between the simulated results and observed values. The root mean square error (RMSE) between simulated and observed days from sowing to emergence, emergence to squaring, anthesis to boll opening, and sowing to boll opening was 0.9, 2.2, 1.7, and 2.1 d, respectively, with a mean of 2.1 d, and in all plant sites, the RMSE between simulated and observed days from squaring to boll opening was 1.8-3.7 d, and that from squaring to opening was 4.6-5.8 d.

Gossypium↗

PubMed2005

[Effects of nitrogen supply on flag leaf photosynthesis and grain starch accumulation of wheat from its anthesis to maturity under drought or waterlogging].

In this paper, a cement pool culture experiment with three water treatments (waterlogging, drought, and moderate water supply) and two nitrogen levels (120 and 240 kg x hm(-2)) was conducted to study the effects of nitrogen supply on the flag leaf photosynthesis and grain starch accumulation of two wheat varieties from anthesis to maturity under soil drought and waterlogging. In comparing with moderate water supply, soil drought and waterlogging reduced the photosynthesis rate (Pn) and SPAD of flag leaf and dry matter accumulation. Nitrogen supply under drought increased Pn and SPAD, while that under waterlogging was in adverse. The total soluble sugar content in grain was reduced under both drought and waterlogging, while that in leaf was decreased under waterlogging but increased under drought. Under waterlogging, increasing nitrogen application rate reduced starch accumulation. The unit grain weight and the yields of grain and starch were reduced under both drought and waterlogging, but nitrogen application favored them under drought while in adverse under waterlogging. It was indicated that both leaf photosynthesis and grain starch accumulation could be regulated by nitrogen supply under stress of soil drought or waterlogging from anthesis to maturity of wheat.

Edible Grain↗

PubMed2005

[Quantitative analysis on the relationships between cotton fiber quality and meteorological factors].

With the method of planting cotton by stages at the sites from Yangtze valley to north Xinjiang, this paper studied the effects of air temperature and sunlight on cotton fiber quality in 2002 approximately 2003. The results showed that with increasing latitude, fiber length increased, while micronaire value and soluble sugar content (SSC) decreased. An ecological model describing the relationships of fiber strength, micronaire value and SSC with air temperature and sunlight was built to determine the optimal range and critical value of air temperature during boll development period. If a high quality fiber (length > or = 27 mm) was targeted, the daily mean temperature (DMT) and minimum temperature (Tmin) during this period should be 21.3 approximately 29.7 and 10.7 approximately 21.3 degrees C, respectively, and the daily temperature difference (DTD) should not be > 15.2 degrees C. Fiber length was the longest when the DMT was 25.4 degrees C. If the lowest fiber length was > or = 25 mm, DMT and Tmin should not be lower than 15.5 and 10.7 degrees C, respectively, and DTD should not be over 17.9 degrees C during boll development period.

Cotton Fiber↗

PubMed2004

[Effect of short-term drought on leaf water potential, photosynthesis and dry matter partitioning in paddy rice].

Pot experiments were conducted to study the effect of short-term drought at four rice growth stages on leaf water potential, photosynthesis and dry matter partitioning in paddy rice. The leaf water potential of rice plant under water stress was lower than that of CK, and the difference increased after midday. The predawn leaf water potential of rice plant decreased significantly when soil water content or soil water potential went down a threshold value, resulted in an obvious decline in the single leaf net photosynthetic rate. In compared with the well-watered treatment, the net photosynthetic rate under severe water stress decreased by more than 50%. The partitioning indexes of leaf, root and spike decreased, while that of stem and sheath increased after short-term drought.

Disasters↗

PubMed2004

[Accumulation pattern of dry matter, nitrogen, phosphorus, potassium and silicon in rice genotypes and their relationships].

The accumulation of dry matter, nitrogen, phosphorus, potassium and silicon in 30 rice genotypes and their relationships under field condition were studied. The results showed that dry matter accumulated at ripening stage linearly increased with increase of nitrogen, phosphorus, potassium and silicon accumulation with highly significant correlation coefficients at both early and late season. At the same time balance of nitrogen, phosphorus, potassium and silicon accumulation was beneficial for dry matter accumulation, which linearly increased with increase of nutrient balance index and decreased with increase of nutrient deviation index. The nitrogen, phosphorus, potassium and silicon were accumulated at the rate of 3.76:1:4.55:7.10 at early season and 2.88:1:4.54:8.09 at late season. During growth period, dry matter accumulation was the highest at middle stage, then late stage and early stage. But nitrogen accumulation was the highest at early stage, then middle stage and late stage. The dry matter accumulated before heading was mainly distributed in stem and leaf sheath, with the highest ratio of stem and leaf sheath to total dry matter at heading stage. In contrast, nitrogen accumulated before heading was mainly distributed in leaf blade, and the ratio of nitrogen in leaf blade to total nitrogen was higher than that of dry matter at either growth stages. Dry matter, nitrogen, phosphorus accumulated at ripening stage were mainly distributed in panicle with rates of 58.01%, 66.42% and 70.06%, respectively. But potassium accumulated at ripening stage was mainly distributed in stem and leaf sheath with the rate of 62.08%. Silicon was largely distributed in stem and leaf sheath at early season with the rate of 43.11%, but distributed largely in panicle at late season with the rate of 46.99%.

Genotype↗

PubMed2004

[A dynamic knowledge model for wheat target yield design and variety selection].

Based on integrating the effects of yield potential of photosynthesis and temperature, average yield level of last three years, soil fertility, fertilization and water management level and production technology level on yield increment, the dynamic yield increment index was quantified and a wheat knowledge model for design of target yield under different temporal and spatial environments was developed through knowledge engineering and system analysis method. By quantitatively calculating suitability of variety characteristics to environmental conditions and production requirements, a knowledge model for variety selection was established. Case studies on the target yield design with the data sets of five different eco-sites, three climatic years and average yield levels of last three years, two soil fertility levels and three fertilization and water management levels, and on suitable variety selection models with the data sets of five different eco-sites, normal climatic year and fifteen typical varieties indicated a good performance of the model system in decision-making and wide applicability.

Crops, Agricultural↗

PubMed2004

[Effect of enhanced ammonium nutrition (EAN) at different growth stages on wheat growth and nitrogen utilization].

Field experiments were conducted in 1998-2000 to investigate the effects of EAN applied at different growth stages (basal, tillering, jointing, booting and whole growth stage) on wheat growth and nitrogen utilization. Compared with single NO3-, EAN as basal fertilizer, tillering dressing and jointing dressing promoted dry matter and nitrogen accumulation after heading, LAI at booting stage, and chlorophyll content of wheat. Grain yield was also increased significantly. Nevertheless, there was no obvious promoting effect of EAN at booting dressing. No significant response of plant growth under EAN was observed over whole growth stage, compared with EAN at early stages, indicating that EAN after jointing was not effective to increase nitrogen utilization and wheat growth. But, it was more effective on decreasing N leaching than other EAN treatments. All EAN treatments increased nitrogen flow efficiency (NFE) and nitrogen recovery efficiency (NRE), compared with single NO-, but EAN treatments before jointing had significant effects on increasing nitrogen utilization. Besides these, EAN a sjointing dressing improved the leaf photosynthetic characteristics during the late developmental stage and the remobilization of dry matter to grain, while EAN a s basal fertilizer an d tillering dressing was more related to increased tillering.

Fertilizers↗

PubMed2004

[A dynamic knowledge model for nitrogen and water management of cotton].

Through analyzing and extracting the newest research results on nitrogen and water management of cotton, a dynamic knowledge model for decision-making on total nitrogen and water supply levels and their distribution among main growth stages of cotton under different environments and yield targets was developed, with the principles of nitrogen balance and water demand and by integrating the factors of climate, soil, yield and variety. Case studies on the knowledge model with the experiment data sets of different eco-sites, varieties and soil characters indicated a good model performance in decision-making and applicability.

Fertilizers↗

PubMed2004

[A dynamic knowledge model for designing suitable sowing date of rice].

Based on the summarization, induction and extraction of dynamic relationships between growth characteristics, variety type, farming system and ecological conditions via reading literature and consulting experts, a knowledge model for designing the suitable sowing date of rice under varied environments was developed through knowledge engineering and system analysis methods. The model could precisely quantify the suitable sowing date under different environments and production systems. Case studies for the model with the data sets of daily weather conditions, typical varieties, seedling nursery methods and farming systems at 7 different eco-sites indicated a good performance of the model system in decision-making and its wide applicability, and the model could help farmers to use the resources such as sunshine and water effectively.

Algorithms↗

PubMed2004

[Nitrogen use efficiency and its relationship with nitrogen nutrition characteristics of wheat varieties].

Forty wheat varieties were tested at two sites (Xuzhou and Nanjing) to evaluate genotypic and environmental variation of nitrogen use efficiency (NUE) and its relationship with nitrogen nutrition characteristics. It was shown that genotype had significant effect on NUE, but environment had less effect on NRE and NFE. All of the nitrogen nutrition traits were significantly influenced by the interaction of genotype x environment. NFE, as an integrated index reflecting the differences of grain yield and nitrogen utilization among different wheat varieties, was significantly correlated with NRE, NPP and NPS, which indicated that it should be more useful in evaluating nitrogen use efficiency. NFE could be improved by increasing N assimilation and translocation after anthesis to effectively increase the N utilization of wheat.

Genotype↗

PubMed2004

[Spatial variability and quantitative analysis of field factors based on GIS].

The objective of this research was to investigate the variability and the quantitative relationships among soil nutrients and crop growth status and yield. All data were analyzed by both classical statistics and geostatistics based on GIS. Soil properties included soil pH, total N, organic matter, available P and available K, while crop growth status was indicated by SPAD, LAI and SPAD x LAI. All parameters except soil pH exhibited spatial correlation. Soil total N and organic matter, SPAD, LAI and SPAD x LAI were all correlated to rice yield. Kriged interpolation maps provided good indication of the spatial variability in crop yield and growth status. Spatial interpolation and correlation analysis proved that SPAD x LAI was more indicative of crop growth status than individual variables, and useful for implementing growth season and topdressing as needed.

Biomass↗

PubMed2004

[Relationship between canopy reflectance and plant water status of wheat].

The study on the relationship between canopy reflectance characteristics and plant water status of wheat under different soil water and nitrogen levels showed that the water contents of canopy leaf and plant had a significant correlation with the spectral reflectance of 460-510, 610-680, 1480-1500 and 810-870 nm bands at different growth stages and that of 460-1500 and 560-1480 nm bands over the whole growth period. The correlation degrees of canopy leaf (CL), upper-layer leaf (UL) and lower-layer leaf (LL) water content with spectral index were in the order of CL>LL>UL. In addition, the water contents of canopy leaf and plant after jointing stage were negatively linearly related to the ratio index R(610, 560) and spectral index (R(610, 560)/ND(810, 610)), but positively correlated with the normalized difference index ((R810 - R610)/(R810 + R610)), indicating that spectral index (R(610, 560)/ND(810, 610)) could be a good indicator for monitoring water status in wheat plant.

Nitrogen↗

PubMed2003

[Effect of enhanced ammonium nutrition on photosynthesis and nitrate reductase and glutamine synthetase activities of winter wheat].

A controlled hydroponics experiment was conducted to investigate the effects of three NH4+/NO3- ratios (0/100, 50/50 and 100/0) on the photosynthesis and the key nitrogen metabolism enzymes of three wheat cultivars with different sensitivity to enhanced ammonium nutrition (EAN). Compared with NO3- alone, EAN significantly increased the leaf chlorophyll content, net photosynthetic rate, and soluble sugar content. It also significantly increased the soluble protein content in leaves and roots and the nitrate reductase activity in leaves, but had no significant effect on Glutamine synthetase (GS) activity. EAN increased the soluble sugar content in leaves, and correspondingly, enhanced the net photosynthetic rate and maintained a higher soluble sugar/protein in leaves and roots, which was favorable to the nitrogen assimilation and plant growth.

Chlorophyll↗

PubMed2003

[Effects of genotype and environment on wheat grain quality and protein components].

The variations of grain qualities and protein components of 40 wheat (Triticum aestivum) varieties were studied at three sites in 1998 and 1999. The results showed that there were significant differences among the genotypes in all the quality characters and protein components. The 40 wheat varieties were divided into 6 groups by comprehensive characters, which mainly included semi-hard and soft wheat in the experimental environment. The effects of environment were significant on grain test weight, sedimentation value, and on contents of wet gluten, protein, lysine and protein components, while contents of starch, amylose and gluten index were insensitive to environment. The rational proportion of glutenin to gliadin could be formed under proper environments. The effects of genotype x environment were significant on grain quality, contents of glutenin and gliadin and the proportion of glutenin to gliadin, while not on globulin. Genotype and environment had more effects on flour protein content, gluten content, sedimentation value and 1000-kernel weight than genotype x environment. The differences of protein components among genotypes and environments reflected the variation of grain baking quality in wheat.

Ecology↗

PubMed2002

[Root growth in rice and its response to soil density].

Studies on root growth and vertical distribution at tillering(TL), panicle initiation(PI), flowering(FL) and mature(MT) stages and effects of soil compaction on root growth were carried out with hybrid rice of Shanyou 63 and 65,002 in root box. The results indicated that root weight reached maximum at flowering stage and then decreased. With the advance of growth stage, percentage of deep roots(20-45 cm in soil) increased. Root weight increased at highest rate and deep roots formed during the period of TL to PI. With increased soil weight density below 20 cm, root weight and percentage of deep roots markedly decreased.

Crops, Agricultural↗