The effects of different concentrations of manganous sulphate on root growth,cell division,chromosome and nucleus morphplogy and nucleoli in root tip-cells of Allium cepa L.were studied.With increasing the concentration of Mn and duration of treatment,manganese inhibited root growth and cell division,and had toxic effects on chromosomes,nuclei and nucleoli.Manganese Could induce mitotic irregularities,comprising cmitosis,anaphase bridges and chromosome stickiness.The nuclei became irregular in shape and many micronuclei were scattered in the cytoplasm.Some similar silver-stained particulate materials were found scattered in the nucleus in root tip cells.The possible mechanism behind these phenomena is also briefly discussed.

Analysis of influence of spatial trend on calculated genetic correlation coeffi-cient was carried out on winter wheat variety trial of a random block design.The result indicated that significant spatial structure existed in thousand kernel weight and kernels per head of winter wheat.Simulated data based on field data demonstrate that strong spatial trend is one of the important causes for genetic correlation coefficient (absolute value) being greater than 1.We suggested that analysis of spatial structure of field data by geostatistical technology be conducted before calculating genetic correlation coefficient.

The embryo structure of two apomictir lines 296B and SSA-1 has been com-pared in present paper.The apomictic embryo has the same character of lacking (or short) sus-pensor in sorghum,otherwise,the sexual embryo has a long suspensor in the same species.This character as an index of judgement on apomxis was discussed.The same of unsexual embryos in the lack of suspensor suggested that there were some relationships between non-zagotic embryos.

Effects of five incubation temperatures (25℃,28℃,31℃,35℃ and 37℃ for 24 hours) and four incubation time periods (0.4,16 and 24 hours at 35℃) on isolated microspore culture of Chinese cabbage were studied.The results showed that cultured microspores of Chinese cabbage developed into embryos at all the incubation temperatues from 28℃ to 37℃,but the best response to high temperature occured at 35℃.Among the four kinds of time periods,the highest yield of embryos was obtained at the 24h treatment.Therefore,the isolated microspore culture of Chinese cabbege ran be efficiently carried out at 35℃ for 24 hours.

The results indicate that high protoplast quality corresponds to high stress tolerance.The damage of cell membrane is one of the important mechanisms of stress.The protective enzyme system(superoxide dismutase.peroxidase and catalase) plays an important role in stress tolerance.In the research of hormone it is suggested that ABA can induce chilling torlerance,and the mechanism may correlate with the special gene expression.

The effects of iow temperature treatment on seedling growth and POD isozymes were studied using hyacinth bean (Dolichos tablab L.)and Soybean[Glycine max(L.)Merr.]culti-vars as experimental materials.Their seedtings were exposured to 1-4℃ low temperature for 4 days to inhibit growth.The changes of POD isozymes in roots and seedlings were observed after seedlings were exposured to 1-4℃ for 4-8 days.There was a significant linear relation between inhibition of seedling growth and change of POD isozymes in these two kinds of plants.

This paper describes using NIRS to determine CP,NDF,RS,VC in Chinese cabbage (Brassica campestris L.ssp pekinensis).Two hundred and forty-two samples of Chinese cabbage were collected from the main producing areas in China for calibration and prediction of the four constituents above.The results of calibration showed that the multiple correlation coefficients between NIRS and chemical methods were 0.9958,0.9852,0.9821 and 0.9814,and the standard errors were 0.398,0.134,0.098 and 0.51,respectively.The correlation coefficients of prediction were 0.994,0.978,0.974 and 0.981,and standard errors were 0.353,0.127,0.108 and 0.548,respectively.These results indicate that NIRS can be used to determine the four constituents of Chinese cabbage as accurately as chemical methods.

The feasibility of distinguishing male and female silkworm chrysalis in cocoon by NIR with fiber optics was discussed.Altogether 187 samples were taken from which 100 samples were used for calibration and others for prediction."1"and"0"were designed as male and female silkworm chrysalis,respectively,for regression.Statistical analysis results showed that MR was 0.930 and SEC 0.189.The prediction results of 87 samples indicated that R was 0.937 and SEP 0.175 respectively.The accuracy of distinguishing sex of silkworm chrysalis in cocoon reached 98.9%.At the same time,it is possible to discriminate the dead silkworm pupa in cocoon immediately through the spectrum.

A wheat breeding model for high yield in the middle and south of Hebei Province was developed.Wheat variety Ji 84-5418 has been bred on this model.The analysis results of high-yield and stability indicated that Ji 84-5418 was not only an aggregate of varied excellent characters,but a recombined biotype which could early differentiate spike and develop coordi-nately,and had better self-regulation ability and potential high productivity.Its yield is stable at 6000-8250 kg/ha.

Three male-sterile soybean (MS) groups were selected out through various methods.A number of filial generations and hybrid strains with special characters were obtained by the methods of isolated plot and backcross.Among them Jinping 1 and Jinping 2,two sister lines,with higher production,big and pretty seed,green coat and a rich perfume,are suitable to a vegetable in city.It was proved that the MS have wide utilization potential as follows;(a)the MS could solve a lot of troubles of artificial cross;for instance,the green seed coat can be used as a gene marker;(b)the MS showed a high hybrid vigor and its potential ratio ranged from 132% to 347%.

The results of characteristic comparison and principal component analysis showed that the major.characteristics of sesame varieties in Henan province were improved in the past decades.The sesame breeding works in the province were focused on the collection and the screening of the native germplasms from 1950 to 1969 and the mean values of the variety characteristics were the lowest.In 1970s,the pedigree breeding was mainly conducted,which resulted in the release of varieties of various types with better traits.During 1980s,the hybridization breeding was carried out dominantly with the varieties possessing fine traits.Since 1990,there were no better varieties released.To make new progresses,it is essential to renew the breeding method and at the same time to introduce and create special germplasms to widen the genetic background.

Studies indicat that;1.when soil moisture is above 15% and soil temperature is 20-28℃,the condition is benefic for infecting and reproducing of the nematodes.At the same time,this condition is samely needed for the white grubs.the migration ability of the nematodes is lower in soil of field than that in tested soil of the laboratory.But in general,the nematodes appplyed into soil distribute mainly in the ploughed layer and a migration area for them can be formed in the direction of horizontal.observations reveal that invasion time of the S.glaseri NC34 into larval (H.parallela) through intersegmental membrane of body segment and foot after the inoculation is 30 min,and it for invading cuticle of larvae body side is 120 min.But the infection time is different in the different individuals of S.glaseri and in the different species of grubs.

Studies in tobacco fields were conducted in 1993.The results showed that the distribution pattern of the larva was aggregative,and the aggregation did not change with the densities of population of the larva.The characteristics of the vertical distribution of the larva on tobacco plants was more in the lower leaves than in the upper.The difference of population density among the tobacco fields with an elevation of 490 meters and 900 meters was not significant.The number of sampling was given under different precisions by using two-stage sampling technique.

The occurrence regularity of wheat midgec (Sitodiplosis mosellana Gehin) was investigated in 1986-1991.One generation of this kind of insects emergies every year,and its cocoon lies dormant in soil through the winter and summer (total for over ten months).The active larvae have a habit to move up and down with the changes of soil temperature.The field experiment over three years has showed that DDVp,a slow-release pesticide,is significantly effective in reduction of wheat loss due to this pest.Thirteen wheat varieties which are resistant or tolerant to this pest have been obtained in Hebei province.The main points of the technique described in this paper is put in a nutshell:relying mainly on growing the resistant varieties of wheat while making chemical control subsidiary.The chemical control is carried out at the pupal stage to kill the insects as many as possible,and at the adult stage to wipe out the remnants.Over the last three years,as a result of the utilization of this technique in larg

From 1986 to 1990 typical physiological races of Piricularia oryzae were chosen from 7 local groups,and the resistance spectrum for 768 rice varieties (strains) was determined.The resistance percentage of 34 varieties constituting 4.4% of the total was up to 80-100%,while that of 109 moderate res.

Control effect of boring pests on fruit trees by high-pressure injection of pesticides.

Two varieties of winter wheat,Bei Nong 2(B.N.2)and Jing 411(J.411),were selected for osmotic adjustment study.At wheat growing stages,from recovery period to mature period,leaf relative water content(LRWC),water potential(LWP)and saturated osmotic potential (LSOP) were positively correlated.

Nutritional accumulation mainly occurres from growth stage 2 to stage 3(lotus-setting stage to early heading stage,48-72 days after transplanting)in Chinese cabbage.The uptake ratio of N and K is nearly l:l,and their uptake amounts are obviously higher than that of P.Balanced fertilization.especially the suitable combination of N and K,is important for the production of high yield and high quality.

With pot-culture method,effects of volume weight of soil on corn growth and yield had been studied.The results indicated that corn yield had shown quadratic relation with volume weight of soil,and the top yield appeared in the condition of soil volume weight.Responses of leaf area,dry matter weight of aerial part,ear grain number and thousand-grain weight of corn to volume weight of soil were in keeping with that of the yield.Volume weight of soil showed significant or ultra-significant linear relation with the corn root length,root diameter,root number and root dry weight.

After ground-mulching in plastic house.it is shown that it may display obvious effect on soil temperature.increase,but almost no effect on the internal air temperature,and light conditions can be improved,but the side effects were presented on the relative humidity and the concentration of carbon dioxide.