以江苏省近60年生产上应用的16个代表性中籼品种(含杂交稻组合)为材料，依品种应用时期结合株型和基因型，将供试品种分为早期高秆（ET）、改良高秆（IT）、矮秆（DC）、半矮秆常规品种（SDC）、半矮秆杂交稻（SDH）和超级稻（SR）6个类型，研究其产量、源库关系和株型变化特性。结果表明，随着品种改良，籽粒产量逐步提高。这主要是由于总颖花量的增加，其关键在于每穗粒数的增多；结实率以DC最高，SR最低，千粒重变化不大。由ET到DC，植株高度降低，生物产量与收获指数同步提高，收获指数的提高更为明显。由DC到SR，植株高度略有增加，生物产量明显提高，抽穗后增加的量尤为显著，收获指数变化较小。品种改良明显减小了顶部3叶的着生角度，增加了抽穗期的叶面积，但颖花量的增加超过叶面积的增加，导致粒叶比（颖花数与叶面积之比）提高。随品种的演进，抽穗期根重以及根冠比提高，但根系伤流液量减少。抽穗至成熟根系伤流液和叶片中玉米素＋玉米素核苷浓度下降的速度表现为SR>SDH>SDC。依据品种演进特征，对进一步提高产量的途径进行了讨论。
Rice is a most important food crop in China and its grain yield per hectare has been over 6 ton in recent years, which is 65% higher than that of the world, on average. Improvement in rice cultivars plays an important role in the increase of the grain yield. However, little is known about physiological and agronomical features responsible for the improvement. In this study, 16 typical mid-season indica rice cultivars (including hybrid combinations) applied in the production in Jiangsu Province during the last 60 years were used, and classified into six types of early tall (ET), improved tall (IT), dwarf cultivars (DC), semi-dwarf cultivars (SDC), semi-dwarf hybrid (SDH), and super rice (SR), according to their application times, plant types and genotypes. All the tested cultivars were grown in the field and the evolution characteristics of grain yield and its components, source-sink relationships and plant types were investigated. Results showed that grain yield was progressively increased with the evolution of the cultivars. Increase in grain yield was attributed mainly to the increase in total number of spikelets, which resulted mainly from large panicles. DC had the greatest, whereas SR had the least, percentage of filled grains. There was no significant difference in 1000-grain weight among the six types of cultivars. From ET to DC, plant height was reduced and biomass and harvest index were simultaneously increased, especially the harvest index increased more. From DC to SR, plant height was a little increased, and biomass dramatically increased, especially after heading, and harvest index a little changed. Improvement of rice cultivars significantly reduced the leaf angle of the top three leaves on stems and increased leaf area at heading. Increase in spikelets, however, was more than that in leaf area, which resulted in the increase of grain-leaf ratio (the ratio of total spikelet number to leaf area at heading). With the improvement of rice cultivars, root dry weight and the ratio of root to shoot were increased, but the amount of root bleeding sap was reduced. The speed of reduction in the concentration of zeatin and zeatin riboside in root bleeding sap and leaves from heading to maturity was SR>SDH>SDC. The results suggest that enlargement of sink resulted from large panicles, increase in biomass especially from heading to maturity and improvement of plant type contribute to the increase of grain yield for modern rice cultivars. Low root activity may account for the low percentage of filled grains for SR. Approaches to further increase in grain yield of rice were discussed based on the evolution characteristics of the cultivars.
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