烤烟根系分泌物对烤烟幼苗生长和养分吸收的影响

连作是烟草栽培中的普遍现象,已引起生长抑制、产量下降和品质恶化等问题。本试验采用溶液培养的方法,在培养液中分别加入未分组和分组后的烤烟根系分泌物,研究根系分泌物对烤烟幼苗生长和养分吸收的影响。结果表明,加入未分组的烤烟根系分泌物显著抑制幼苗的生长,降低根系活力,并随加入量的增加抑制作用增强;加入酸溶性、碱溶性、中性组分的根系分泌物,均降低幼苗根系活力,以中性组分的抑制作用较强。三种不同组分的根系分泌物均显著降低根系对NO3-、PO43-、K+离子的吸收,其中中性组分对NO3-吸收的影响最大,而酸溶性组分对K+的吸收抑制作用较强。推测在烤烟根系分泌物中,可能存在多种抑制烤烟生长和养分吸收的化学物质。

Effects of root exudates on growth and nutrients uptake of tobacco seedlings

Continuous cropping,which is commonly practiced in the tobacco cultivation areas of china,brought about a number of problems on tobacco production,such as growth inhibition,yield decline and quality deterioration.Allelopathy of root exudates is regarded as a reason for these problems in some crops;however,the role of root exudates on tobacco production is still not very clear.We conducted a hydroponics experiment to study the effects of root exudates on the growth and uptake nutrients of tobacco seedling.Root exudates were obtained directly from the culture solution of adult tobacco seedling,and then fractionated into acid soluble,alkaline soluable and neutral groups.Therefore,these fractionated solutions with the un-fractionated root exudates solution were added into the culture solutions of young seedlings with four leaves,respectively.The control treatment was also set up without root exudates component added.The results showed that un-fractionated root exudates inhibited greatly the growth and root activities of the seedlings from day 20,and the effect of root exudates increased dramatically with increasing amount the root exudates added.The added fractionated root exudates,especially in neutral one,depressed root activities. All of these fractionated materials declined significantly NO-3,H2PO-4,K uptake.It was observed that the most depressed NO-3 and K uptake was occurred with the addition of neutral acid fraction,respectively.As a consequence, It was inferred that several chemical inhibitors of growth and nutrient uptake of tobacco seedlings should be contained in root exudates.