Accumulation and distribution of dry matter and potassium in maize varieties released in different years

In order to compare the differences in growth, development and dry matter accumulation, as well as potassium (K) uptake and distribution in different maize varieties released in different years in China, field experiment was conducted under the same conditions and six maize cultivars released from the 50s in last century until now were employed, e.g. Baimaya, Jinhuanghou, Zhongdan 2, Tangkang 5, Nongda108 and Zhengdan 958The result showed that new varieties had slower developmental process, longer growth duration, larger total leaf area and slower leaf senescence, compared with those of the old varieties. At V10 stage, there was no difference in plant dry weights among different maize varieties. After this stage, however, new varieties grew quicker and their dry weights increased faster than those of the old varieties. The high rate in dry matter gain of all varieties appeared after silking. The grain dry weights of all varieties were about the same as the dry matter gains of whole plants after silking, indicating that dry matter accumulated in grains was directly from the leaf photosynthesis after silking. In spite of the same plant dry weights at V10 stage, K contents in maize varieties released in different years already showed difference at this stage, and that was higher in the new varieties than those in the old varieties. Most of K in plants of all maize varieties was taken up before silking. There was even decrease in K content in old varieties Baimaya and Jinhuanghou from silking until maturity. K deposited in grains of different maize varieties came mainly from the retranslocation from the vegetative organs, especially from leaves. There was even more K retranslocated from the leaves of the straygreen varieties Nongda108 and Zhengdan 958 than that form the old varieties. In summary, new varieties had longer growth period, larger leaf area and slower leaf senescence, which were beneficial for grain milking and thus higher grain yield formation. Since the high rate in dry weight gain appeared after silking, while the most of K in plants of all maize varieties was taken up before silking, the dry matter and K accumulation in maize plants was not synchronized. Grain dry matter came mainly from the photosynthesis after silking, while grain K came from the retranslocation from the vegetative organs, regardless of the difference in varieties.