Growth Suppression of Canola Through Wheat Stubble I. Separating Physical and Biochemical Causes in the Field

A field experiment was conducted to investigate the causes of poor canola growth through surface-retained wheat stubble. The experiment was designed to separate the role of biochemical factors such as stubble phytotoxicity, nitrogen (N) immobilisation and disease incidence from the physical effects of the stubble including changes in the seedbed microclimate on crop growth and yield, as these had been previously identified as possible mechanisms for the poor growth. Treatments included: two stubble cultivars, three levels of decomposition, two levels of nitrogen and inert plastic mulch. A novel approach involving leachates collected from intact field cores with a rainfall simulator was also used to assess the phytotoxic impacts of the stubble. Surface-retained wheat stubble (5 t/ha) reduced the canola vegetative biomass by 46% and yield by 26%, consistent with previous field observations. There was no impact of stubble variety or level of stubble decomposition on canola growth and yield, and an inert plastic mulch designed to simulate the physical effects of the wheat stubble had a similar effect on growth and yield as wheat stubble. Leachates collected from intact field cores through surface stubble also had no impact on canola germination or radicle elongation in petri-dishes in the absence of soil, nor on emergence of canola in pots of soil. Together, these observations suggest phytotoxicity was not contributing to the poor growth. N-immobilisation was evident in stubble-retained treatments although tissue N concentrations were adequate in all treatments and the growth limitation could not be overcome with added N. The principal mechanism of growth reduction was associated with the physical impact of the stubble including a reduction in photosynthetically active radiation, the red:far red ratio of incident light under the stubble, and the temperature above the stubble layer. These effects led to elongated hypocotyls, reduced investment in early leaf and root growth, delayed emergence and slower leaf area development as well as an increase in seedling disease complex, effects apparent in both wheat stubble and inert plastic mulch treatments. The results suggest that physical, rather than biochemical factors are the main cause of poor growth of canola in surface-retained wheat stubble, and that much of the impact could be avoided if the stubble were moved away from directly above the emerging seedlings.     

The Connection between High Energy and Low Energy Responses to Red and Far-Red Light of Hypocotyl Elongation in Red Cabbage Seedlings (Brassica oleracea var. capitata'Marner Septemberrot')

Growth responses of hypocotyls of Brassica oleracea L. var. capitata caused by diurnal irradiation of various duration (0.5 h/d up to continuous irradiation) and various irradiance (0.3–1.5 W m^?2) with red and far-red light from sources characterized below can be described by the equation: (W= relative effect, I= irradiance, t₁= irradiation time per day, W_s= constant dependent on material and wavelength, α, B and t_s, = constants dependent on wavelength.) On the basis of that equation a possible connection between longtime and short-time irradiation responses is discussed.     

红光抑制绿豆下胚轴伸长时富含羟脯氨酸蛋白质的含量变化

红光能增加细胞壁的Hyp含量和细胞各部分的Hyp／Pro,绿豆下胚轴切段伸长被红光抑制的程度与两者是正相关。环己酰亚胺和放线菌素D明显降低细胞壁的Hyp含量,提高WSFC和CWRSE中的Hyp／Pro,抑制切段伸长。香豆素不仅显著减少细胞壁的Hyp含量,而且降低WSFC和CWRSE中的Hyp／Pro,促进下胚轴伸长。α,α．二吡啶降低细胞壁的Hyp含量和WSFC中的Hyp／Pro,解除红光对切段伸长的抑制。EGTA、verapamil、La3 和A23187均可解除红光抑制切段伸长的作用,但对细胞壁的Hyp含量和细胞三部分蛋白质中Hyp／Pro影响较小。     

麦秸覆盖夏玉米对其苗期生长发育的生化他感作用研究初报

麦秸覆盖夏玉米对其苗期生长发育的生化他感作用研究初报张玉铭,马永清（中国科学院石家在农业现代化研究所,０５００２１）ＡｌｌｅｌｏｐａｔｈｉｃＥｆｆｅｃｔｏｆＷｈｅａｔＳｔｒａｗＭｕｌｃｈｉｎｇｏｎＳｅｅｄｌｉｎｇＧｒｏｗｔｈａｎｄＤｅｖｅｌｏｐｍｅｎ...