Temporal and Spatial Dynamics of Organ Water Content in Maize with Different Senescence Types.

Understanding the water status of specific organs can be helpful in evaluating the life activities and growth conditions of maize. To accurately judge organ growth conditions and thus design appropriate interventions, it is necessary to clarify the true water dynamics of each maize organ. Using multiple maize cultivars with different growth periods, spatio-temporal water dynamics were analyzed here in the leaves, stalks, and ear components. Leaf water content was found to gradually decrease from both the bottom and top of the plant to the middle, whereas stalk water content decreased sequentially from the top to the bottom. Each successively higher node from the bottom of the plant was associated with decreases of 0.99% and 1.27% water content in the leaves and stalks, respectively. The water dynamics in leaves and internodes showed three clear stages: the slow loss, rapid loss, and balance stage. A water content of 60% appeared to be an irreversible turning point for initiation of senescence. Using normalized growth period as a measure, each of the tested cultivars could be assigned into one of two types based on their water dynamics: stay-water or general type. General-type cultivars had a shorter duration with a high water content and a water loss rate approximately twice as high as that of the stay-water type. This may have been related to the leaf senescence characteristics. However, the stay-water trait did not interfere with water dynamics of the ear components. Therefore, it may not be robust to evaluate the kernel dehydration of maize according to leaf senescence conditions due to the weak correlation between kernel water content and leaf senescence characteristics.

[Monitoring canopy nitrogen status in winter wheat of growth anaphase with hyperspectral remote sensing].

Biomass, leaf area index (LAI) and nitrogen status are important parameters for indicating crop growth potential and photosynthetic productivity in wheat. Nondestructive, quick assessment of leaf dry weight, LAI and nitrogen content is necessary for nitrogen nutrition diagnosis and cultural regulation in wheat production. In order to establish the monitoring model of nitrogen richness in winter wheat of growth anaphase, studying the relationship between the nitrogen richness (NR) containing nitrogen density, LAI and leaf dry weight and the difference of hyperspectral reflectance rates (deltaR), we conducted a comparable experiment with five winter wheat varieties under nitrogen application level of 0, 100, 200 and 400 kg x N x ha(-1). The results indicated the NRs of the different varieties of winter wheat leaves increased with increasing growth stage while in the different nitrogen levels it was sequenced as: NO>N3>N1>N2. Twelve vegetation indices were compared with corresponding NR. The NR had significantly negative correlation to TCARI and VD672 in those vegetation indices, and their correlations (r) arrived at 0.870 and 0.855, respectively. The coefficients of determination (R2) of two models were 0.757 and 0.731 by erecting model with the two indexes and NR Root mean square error (RMSE), relative error (RE) and determination coefficient between measured and estimated NR were employed to test the model reliability and predicting accuracy. Accuracy rates of the models based on TCARI and VD672 achieved 84.56% and 80.13%. The overall results suggested that leaf nitrogen status of growth anaphase in winter wheat has stable relationships with some vegetation indexes, especially index of TCARI and VD672.

[Characteristics of accumulated temperature demand and its utilization of maize under different ecological conditions in northeast China].

To understand the accumulated temperature (ACT) demand of maize for its normal maturation among years and regions as well as the use efficiency of local ACT, a group of work-net field experiments was conducted at 55 sites in 28 regions of Northeast China spring maize planting area (40 degrees 07'-48 degrees 08' N) in 2007-2009, taking an eurychoric maize variety Zhengdan 958 as test object. The meteorological conditions in the area had large difference. In the same regions, the active accumulated temperature above 10 degrees C in whole corn growth season (ACT10 for short) demand of Zhengdan 958 for completing its whole growth and development process had little difference among different years (P > 0.1). However, in different regions, this demand differed significantly (P < 0. 001) in the same years, with the largest difference occurred from seedling stage to emergence stage, followed by at post-silking stage, and the least at pre-silking stage. The maturity degree of Zhengdan 958 had significant correlations with local heat conditions, and there was a linear relationship between use efficiency and latitude. Zhengdan 958 could be safely matured in the regions with the ACT10 being more than 3000 degrees C, and had a risk of immaturity in the regions with the ACT10 less than 3000 degrees C. In conclusion, under certain meteorological conditions, the ACT demand of Zhengdan 958 for completing its growth process was relatively stable, and, due to the self physiological adjusting, the ACT10 demand of Zhengdan 958 at its different growth stages showed a significant difference among different regions.