Improving grain yield (GY) and reducing grain moisture (GM) are urgent demands for directly harvesting kernels with combine harvesters in maize production.  GY and GM are both related to leaf, stem and root characteristics, but the relationships are not fully understood.  To better understand these relationships, we conducted a field trial involving 12 maize hybrids with two sowing dates in 2017 and 10 maize hybrids with one sowing date in 2019.  GY ranged from 6.5–14.6 t ha^–1 in early-sown varieties and 9.3–12.7 t ha^–1 in late-sown varieties in 2017, and 5.9–7.4 t ha^–1 in 2019, respectively, with corresponding GM variations of 29.8–34.9%, 29.4–34.5% and 31.9–37.1% at harvest.  A large maximum leaf area contributed to a high yield, a fast leaf senescence rate accelerated grain dehydration in the late growth period, and a compact root structure resulted in both of high-yield and fast-grain dehydration.  A strong stem improved lodging resistance but maintained a high GM at harvest, and it is challenging to combine high GY and low GM in maize.  High GY co-existed with low GM in some varieties that should have a rapid grain filling, a relatively long grain-filling duration, and a rapid grain dehydration in the late growth period.  A high daily temperature in the late growth period also improved GY and reduced GM by influencing grain filling and dehydration, suggesting that adjusting the sowing date should be an alternative strategy to combine high GY and low GM in kernel harvesting. 

Leaf growth and its interaction with the growing environment critically affect leaf area, distribution, and function, and ultimately affects grain yield of maize (Zea mays L.).  To detect the effects of leaf area dynamics, growth periods, and the environment on maize grain yield, a three-year field experiment was conducted using two maize varieties, medium plant-size variety Zhengdan 958 (ZD958) and large plant-size variety Zhongnongda 4 (ZND4), and three to five sowing dates.  The sowing date significantly affected maize yield as a result of changes in leaf area, growth stage, and growing environment.  Prior to the 12th leaf stage, significant correlations between leaf area dynamics, environment, and yield were seldom detected.  The expansion of leaf area from 12th leaf stage to silking stage was significantly positively correlated with growing degree days (GDD), solar radiation, and grain yield, indicating the importance of leaf area dynamics during this period.  After silking, solar radiation played a more important role in inducing leaf senescence than GDD, particularly in the 2nd half of the grain filling stage.  Accelerated leaf senescence in late growth period can increase maize yield.  The environment affected leaf area dynamics and yield of the large plant-size variety (ZND4) more easily than the medium plant-size variety (ZD958) at the optimum plant density, reflecting the difference in varietal capacity to adapt to the growing environment.  This study indicates that optimizing the interaction among leaf area dynamics, growth periods, and environment is a sound strategy to increase maize yield.  Favorable interactions are useful to determine the optimal sowing date of a given variety.

Maize growth and development is affected by low temperature (LT) especially at the early stages of development.  To describe the response of different varieties to LT stress and determine an effective method to cope with LT stress, maize hybrids
Zhengdan 958 (ZD 958) and Danyu 39 (DY 39) were planted and grown at 10 and 25°C, respectively.  Effects of the chemicals potassium chloride (KCl), gibberellin (GA₃), 2-diethylaminoethyl-3,4-dichlorophenylether (DCPTA), and all three combined chemicals (KGD) on coping with LT stress were tested by seed priming.  The varieties performed significantly different at 10°C.  Compared to leaf, root growth was more severely affected by LT stress.  Root/leaf ratio is likely a more reliable parameter to evaluate cold tolerance based on its close correlation with leaf malondialdehyde (MDA) content (R=–0.8).  GA₃ advanced seed germination by about 2 days compared with control treatment of water.  GA₃ and DCPTA both resulted in lower leaf MDA content and higher leaf and root area, and root/leaf ratio.  KCl resulted in the highest evenness of plant height.  KGD performed the best in increasing cold tolerance of maize morphologically and physiologically.  Strategies to increase maize tolerance of cold stress, such as variety breeding or chemical selection, would increase maize yield especially at high-latitude regions and have great implications for food security.