Because of the rapid development of transgenic maize, the potential effect of transgene flow on seed purity has become a major concern in public and scientific communities. Setting a proper isolation distance in field experiments and seed production is a possible solution to meet seed-quality standards and ensure adventitious contamination of products is below a specific threshold. By using a Gaussian plume model as basis and data recorded by meteorological stations as input, we have established a simple regionally applicable maize gene-flow model for prediction of the maximum threshold distances (MTD) at which gene-flow frequency is equal to or lower than a threshold value of 1 or 0.1 % (MTD1%, MTD0.1%). After optimization of the model variables, simulated outcrossing rate was a good fit to data obtained from field experiments (y = 1.156x, R (2) = 0.8913, n = 30, P < P 0.01). In the process of model calibration, it was found that only 15.82 % of the total amount of the pollen released by each plant participated in the dispersal process. The variable "a" for genetic pollen competitiveness between donor and recipient was introduced into our model, for the "Zinuo18" and "Su608" used, "a" was 17.47. Finally, the model was successfully used in the spring maize-growing region of Northeast China. The range of MTD1% and MTD0.1% in this region varied from 10 m to 49 m and from 17 m to 125 m, respectively.

No abstract

Heat stress is one of the common agrometeorological hazards in rice production in the middle and lower reaches of the Yangtze River in China. To study the mechanism of mist spray in ameliorating heat stress injury, a field experiment was conducted at Nanjing (China) with an early and a late hybrid rice varieties (Oryza sativa L.). The mist spray treatments were conducted at the flowering period, which were at August 6-10 for early rice variety and September 1-5 for late one. Four treatments at different irrigation times (T1: 08:00; T2: 12:00; T3: 14:00; CK: no mist spray; mist spray amount of 1 L·m−2) were included. The temperature and humidity at the different heights of the rice canopy and the net solar radiation above the canopy were measured. The leaf senescence, chlorophyll content, photosynthetic rate and the yields of the rice were determined. The results showed that mist spray rapidly reduced the temperature and increased the relative humidity in the canopy. The cooling effect was most significant at the top of the canopy and decreased downward from the top of canopy. The duration of the temperature decrease caused by the mist spray was 2 h. Mist spray could lead to an increase in latent heat flux (LE) and a decrease in sensible heat flux (H) in the rice field. The mist spray treatments delayed the senescence of the rice leaves, increased the activity levels of the superoxide dismutase, peroxidase, catalase, and soluble protein, reduced the malondialdehyde content, increased leaf chlorophyll content, photosynthetic rate and yield. The T2 treatment showed the most significant effect against heat stress, with the yield of the two varieties increased 13.7 and 13.6% respectively. Compared with mist spray at 08:00 or 14:00, spraying at 12:00 had the strongest resistance to heat stress in rice field.

No abstract

Abstract. In this paper we will prove a uniformity result for the Iitaka fibration f : X → Y , provided that the generic fiber has a good minimal model and the variation of f is zero or that κ(X) = dimX − 1.