Identification Indexes Evaluation And Response To Alkali Stress Of Early Japonica Rice In Cold Region

The experiment is carried out in Jiamusi rice research institute of Heilongjiang academyof agricultural sciences in2010-2011.173varieties which are suitable for the cultivation ofHeilongjiang Province are collected from domestic and foreign country. Research of Alkaliresistance and assessment of identification index are proceed in buds period, seeding stageand mature stage. In this paper the response mechanism of soda alkali stress and classificationof some test material are discussed from aspect of morphology, physiology, yield trait andultrastructure. Changes of root-cells-morphological and ultrastructure and formation of thedifferent damage mechanisms among different genotype varieties are evaluated after stressfrom the microscopic point of view. The main conclusion and views are as follow:1. The radicle is the most sensitive to the alkali stress at germinating stage. There is nocorrelation between the changes of coleoptiles and alkali resistance. The main indexes whichdefined alkali resistance level are relative shoot length, relative radicle length, relative radiclenumber, relative shoot dry weight and relative radicle dry weight. Based on that, thedetermine equation of alkali resistance isY=11.251-3.6747X1-1.641X2-1.179X3-3.900X4-1.973X5during that7days, and thedetermine equation of alkali resistance is Y=9.234-4.506X1-2.167X2-2.621X3which is builtbased on three key index, relative shoot length, relative shoot dry weight and relative rootsdry weight.2. After0.20%mixed alkali treatment, the length of shoot and root length are showed adownward trend and significant inhibition to root elongation and growth， but there is nocorrelation in susceptibility for alkali stress between aboveground and underground parts.Many physiological indicators changed during the alkali stress treatment such as the leaf ageprocess delayed, the reduction of leaf area, green leaf number, root dry weight, canopy drymatter accumulation and root-shoot ratio, meanwhile the leaf length and area are increasedand the leaf width is declined. Some indexes can serve as indicator of alkali resistance at ricegerminating stage, such as the changes of leaf area per plant and relative value of green leafnumber, root shoot ratio and root shoot length ratio. A significant effect is occurred on the leafpigment synthesis, descending order is chlorophyll A, chlorophyll B and carotenoid minimally.The proline content in stems and leaves are increased significantly than that in root underalkali stress. Alkali stress could simulate the activity of protective enzyme of SOD in somevarieties, and also block the functions of SOD synthetic system or the activity of SOD insome varieties. Alkali stress could improve the activity of leaves POD in rice at germinatingstage.3. The regularity and tenseness of root cell is descended, the longitudinal elongation ofroot cell and formation of great vascular bundles are restrained by alkali stress, and also someimmature vascular bundles are formed and roots lignification and branch roots formation arepromoted. Cortex parenchyma cells and part of pericycle cells became necrosis because ofalkali stress; epidermic cells dropped earlier than CK, the stereoscopic impression wouldlower because of the alkali stress. The damage mechanism of alkali stress to rice varieties isdifference based on the observation of the4varieties’ ultrastructure. The damage inchloroplasts and mitochondria are serious and the quantity and size of starch descended InLongjing27, however Suijing5is on the contrary part. Tengxi138’s chloroplasts are moresensitive to Alkali Stress than mitochondria, and the quantity of starch became less. The effects on Koshihikari are complex: the structure of chloroplasts changed obviously, thequantity of anyloplast descended significantly, the structure indistincted, and the inner ridge isnot clear, the quantity of anyloplast became more, and the volume became bigger. Under thealkali stress, the granular osmophilic materials (GOM) of all varieties became more anddarker.4. The effects of alkali stress on plant height and the relative water content of the firstunfold leaf present a trend of fluctuations (increase first then descend) with the treatmentconcentration increasing. A linear downward trend is present at leave pigments content, thevalue of Chlorophyll A/Chlorophyll B, the activity of SOD, the content of vitamin C and thebleeding, regression curve is first-order equation. There are quadratic regression relationshipbetween treatment concentration and many physiological indexes that is the content of proline,soluble sugar, the activity of SOD and CAT. The tendency showed firstly descend thenincrease trend with the treatment concentration increasing. The content of MDA is present astraight line upward trend within the increasing of treatment concentration. The increment ofthe soluble sugar is present gradual upward trend within the increasing of proline. The activityof POD and SOD shows negative linear correlation. With the increasing of alkaliconcentration, relative conductivity in rice leaf present a significant upward trend, besides, asignificant quadratic regression appeared between them.5. The number of panicles per hole and seed setting rate present a floating trend with thechanging of concentration. The number of panicles per hole and seed setting rate increasingwhen treatment are in low concentration level, once the concentration reach or exceed0.10%,the two indicators begin to decrease significantly. The root dry weights, stems and leaves,panicles and plant of rice begin to significantly descend with the concentration increasing.The substance of stems and leaves is primary accumulated in panicles within a certainconcentration range. There is no significant effect when treatment of concentration at lowlevel. However, panicle length descended significantly when the concentration rose to0.15%.The inhibitory action of alkali stress on secondary branches is more effective than that of onprimary branches. However, fail to detect significant difference on grain empty rate.Plumpness of grains descend significantly when treatment of concentration at high level. Thelittle effect is present in thousand grains weight of primary branches when treatmentconcentration of alkali is lower than0.05%. However, a greater impact is present once theconcentration beyond0.05%. The changes of thousand grains weight ratio of secondarybranches and number of secondary branches are on the contrary part. Interference ofsensitivity coefficient is low to the concentration which could be used for evaluating the alkaliresistance of rice. The other index could be considered as reference, such as economiccoefficient, biological alkali resistance coefficient, alkali resistance index and alkali resistancecoefficient. There would be difference in alkali resistance of rice between vegetative growthstage and reproductive growth stage.