Effects Of Soil Moisture On The Development Of Quality

~J~HK~ 2001 ~眫4~ti~ 3 EFFECTS OF SOIL MOISTURE ON THE DEVELOPMENT OF RICE QUALITY Postgraduate: Cat Yixia Supervisor: Prof Zhu Qingsen Prof Yang Jianchang (Agri. College, Yangzhou Univ. Yangzhou 225009) ABSTRACT The experiments were carried out in the pot and filed by rigorously controlling soil water potential with tensionmeters. With Wuxiangjing 9 (a Japonica variety) and Shangyou 63 (an Indica hybrid rice combination) as materials, the effects of different soil water potentials on the main quality characteristics of rice , such as head milled rice, chalkiness, amylose content, and physiological characters were studied, and the changes of quality characteristics in different genotype-rice under heavy water stress were observed. The main results were as follows: 1. During the grain filling period, when the soil water potential (SWP) was reduced to -1 5kPa, the grain quality was improved; while SWP was under -1 5kPa, head milled rice was significantly decreased, both the percentage and degree of chalkiness were significantly increased, there was a conic relationship between gel consistency and SWP, and there was no significant difference among treatments in other quality indices, such as kernel shape, amylase content and protein content. 2. There were obviously changes in spikelet-leaf ratio, chlorophyll content and grain water content during grain-filling period. If the low soil water potential was under - 3OkPa, the relatively increased amounts of spikelet-leaf ratio and chlorophyll content were presented negative effects during the 25?5 days after flowering, dehydration of kernel was very rapid. 3. Under heavy water stress, there was a increasing trend of head milled rice, some varieties were significantly increased; chalkiness varied with cultivars, there was a 4 decreasing trend in indica cultivars and an increasing trend in japonica cultivars; the effects on kernel shape were based on the changes of both kernel length and kernel width; gel consistency was complex, and no regulations could be gained; and there was no significant difference in other indices such as brown rice, milled rice, pasting temperature (alkali spreading value), arnylase content and protein content between heavy water-stressed and well-watered treatment. 4. Some properties of ear and grain were significantly affected by heavy water stress, and varied with genotype, especially in the number of spikelets per panicle, iO~- grain weight, fecundated-grain percentage and filled-grain percentage. There were 4 varieties (yanghan 1, baizhenzhu, beinong95-2 and hang6-235 ) whose properties were not obviously affected by heavy water stress. 5. Heavy water stress significantly affected rice starch viscosity proflles(tested using a Rapid Visco-analyzer, RVA), and there were obvious difference between genotype varieties. There were decreasing trends of RVA profile character such as peak viscosity, hot viscosity, cool viscosity and breakdown in most varieties under heavy water stress, while an increasing trend of consistence in most varieties. According to the changes of breakdown, setback and consistence, the varieties tested could be sorted for 4 groups. The gra...