氮磷营养对旱冬瓜幼苗生长的影响

采用温室盆栽试验，以Hoagland营养液为母液，其中氮（全氮）和磷（全磷）质量浓度分别为210和62mg·L^-1，通过调节营养液中氮和磷的质量浓度，设置了9种氮和磷配比营养液，对旱冬瓜Alnus nepalensis幼苗进行砂培养试验，从而探讨氮和磷营养对旱冬瓜幼苗的苗高、地径生长和生物量的变化及幼苗吸收氮和磷的影响。结果表明：①不同氮磷营养供应水平对旱冬瓜幼苗的生物量累积、地径和苗高生长量有影响，其中氮的影响达显著水平，磷的影响达极显著水平，氮和磷之间的交互作用不明显。在氮和磷营养配合处理时，只要二者之一的供应水平低于母液中的质量浓度，旱冬瓜幼苗的地上部分生长和根系生长都不如对照。②氮营养水平低于210mg·L^-1时。增加营养液中磷的质量浓度。细根／叶生物量比和地下／地上生物量比降低；氮营养水平等于210mg·L^-1时，增加营养液中磷的质量浓度，这2种生物量比增加；磷营养水平低于62mg·L^-1时，低于或高于210mg·L^-1的氮营养水平导致2种生物量比增大。③在50和210mg·L^-1氮营养水平下，增加供磷质量浓度，根和茎中的氮质量分数逐渐降低，当磷水平增到62mg·L^-1时下降为最低，继续增加磷水平，则开始上升；在50mg·L^-1氮水平下，增加供磷水平，叶中的氮质量分数逐渐上升，磷供应达到62mg·L^-1时最有利叶片中氮的积累；在210mg·L^-1氮水平下，同样为磷在62mg·L。水平时最有利于叶片中氮的积累；不论在何种供氮水平下，在供给32mg·L^-1磷水平时，不利于幼苗对磷的吸收，根、茎、叶中的磷质量分数都最低。图4表3参9，

Alnus nepalensis seedling growth with N and P treatments

Nitrogen （N） and phosphorus （P） are important nutrients for tree growth. There is low N and P content of mountain soil in Yunan Province. They maybe affect Alnus nepalensis seedling growth. This aim was to study Alnus nepalensis seedling growth with different N and P supply. Sand culture greenhouse experiments were used to determine the growth response of Alnus nepalensis to three N treatments （50, 210, and 420 mg·L^-1） and four P treatments （14, 32, 62, and 124 mg·L^-1）, of which the control treatment design was 210 mg·L^-1 N and 62 mg·L^-1 P. Split-plot design with 9 treatments and 5 replications was used in the experiment. Results showed： （1） There had significant changes in root biomass, shoot biomass, leaf biomass, height and diameter increments of seedlings with different N and P supply, but no interaction between N and P, of which the effect of N was remarkable （P 〈 0.05）, and P was extreme remarkable （P 〈 0.01 ）. However, when N or P supply was less than the control, seedling growth reduced. （2） With increasing P and with N lower than 210 mg·L^-1, the fine root mass/leaf mass ratio and root mass/ shoot mass ratio was reduced, whereas with N of 210 mg·L^-1 these two ratios increased. （3） Compared to the control, with N of 50 and 210 mg·L^-1 as P increased, N content of roots and shoots decreased, but leaf N increased. （4） For all N treatments, P concentration in roots, shoots, and leaves was lowest with P 32 mg·L^-1 In conclusion, there was an important effect of Alnus nepalensis seedling growth with balanced N and P supply or with increased P from a Hoagland solution. [Ch, 4 fig. 3 tab. 9 ref.]