Influence of plant architecture on maize physiology and yield in the Heilonggang River valley

The size and distribution of leaf area determine light interception in a crop canopy and influence overall photosynthesis and yield. Optimized plant architecture renders modern maize hybrids(Zea mays L.) more productive, owing to their tolerance of high plant densities. To determine physiological and yield response to maize plant architecture, a field experiment was conducted in 2010 and 2011. With the modern maize hybrid ZD958, three plant architectures, namely triangle, diamond and original plants, were included at two plant densities, 60,000 and 90,000 plants ha-1. Triangle and diamond plants were derived from the original plant by spraying the chemical regulator Jindele(active ingredients,ethephon, and cycocel) at different vegetative stages. To assess the effects of plant architecture, a light interception model was developed. Plant height, ear height, leaf size,and leaf orientation of the two regulated plant architectures were significantly reduced or altered compared with those of the original plants. On average across both plant densities and years, the original plants showed higher yield than the triangle and diamond plants,probably because of larger leaf area. The two-year mean grain yield of the original and diamond plants were almost the same at 90,000 plants ha-1(8714 vs. 8798 kg ha-1). The yield increase(up to 5%) of the diamonds plant at high plant densities was a result of increased kernel number per ear, which was likely a consequence of improved plant architecture in the top and middle canopy layers. The optimized light distribution within the canopy can delay leaf senescence, especially for triangle plants. The fraction of incident radiation simulated by the interception model successfully reflected plant architecture traits. Integration of canopy openness is expected to increase the simulation accuracy of the present model. Maize plant architecture with increased tolerance of high densities is probably dependent on the smaller but flatter leaves around the ear.

From the floret to the canopy:High temperature tolerance during flowering

Heat waves induced by climate warming have become common in food-producing regions worldwide,frequently coinciding with high temperature(HT)-sensitive stages of many crops and thus threatening global food security.Understanding the HT sensitivity of reproductive organs is currently of great interest for increasing seed set.The responses of seed set to HT involve multiple processes in both male and female reproductive organs,but we currently lack an integrated and systematic summary of these responses for the world’s three leading food crops(rice,wheat,and maize).In the present work,we define the critical high temperature thresholds for seed set in rice(37.2℃±0.2℃),wheat(27.3℃±0.5℃),and maize(37.9℃±0.4℃)during flowering.We assess the HT sensitivity of these three cereals from the microspore stage to the lag period,including effects of HT on flowering dynamics,floret growth and development,pollination,and fertilization.Our review synthesizes existing knowledge about the effects of HT stress on spikelet opening,anther dehiscence,pollen shedding number,pollen viability,pistil and stigma function,pollen germination on the stigma,and pollen tube elongation.HT-induced spikelet closure and arrest of pollen tube elongation have a catastrophic effect on pollination and fertilization in maize.Rice benefits from pollination under HT stress owing to bottom anther dehiscence and cleistogamy.Cleistogamy and secondary spikelet opening increase the probability of pollination success in wheat under HT stress.However,cereal crops themselves also have protective measures under HT stress.Lower canopy/tissue temperatures compared with air temperatures indicate that cereal crops,especially rice,can partly protect themselves from heat damage.In maize,husk leaves reduce inner ear temperature by about 5℃compared with outer ear temperature,thereby protecting the later phases of pollen tube growth and fertilization processes.These findings have important implications for accurate modeling,optimized crop management,and breeding of new varieties to cope with HT stress in the most important staple crops.