氮水平和形态配比对巴西橡胶树花药苗生长及氮代谢、光合作用的影响

Effects of different nitrogen levels and NH_4^+/NO_3^- ratios on the growth,nitrogen metabolism and photosynthesis of anther-derived somatic seedlings of Hevea brasiliensis

采用砂培方法研究了不同供氮水平及NH4+/NO3-配比对巴西橡胶树花药苗生长、氮代谢及光合作用相关指标的影响。结果表明,随供氮水平的提高,橡胶花药苗茎秆、叶、地上部及单株总干重、植株各部位氮含量和氮积累量、叶绿素含量均相应升高,其中粗根、茎秆、叶片含氮量、单株吸氮量及叶绿素含量各处理间差异均达显著水平;株高、茎粗、细根干重、叶片光合速率先增后减,且以8 mmol/L氮水平时最大;低氮水平下细根硝酸还原酶(NR)活性较高。不同NH4+/NO3-配比试验中,纯NH4+营养下小苗各部位氮含量、氮积累量最高(除细根和叶柄氮的积累量);NH4+/NO3-为75/25时,小苗株高、茎粗、叶柄、叶片、植株地上部及株干重最大,NH4+/NO3-为50/50时,小苗细根干重、茎秆干重、叶绿素含量、光合速率最大,且显著大于纯NO3-营养处理;而NH4+/NO3->50/50时,处理间差异不显著(除细根和茎秆N含量);纯NO3-营养下小苗细根NR活性最高,但生长最弱。结果说明橡胶花药苗不适宜于纯NO3-环境,而适宜于纯NH4+及NH4+/NO3-混合营养,其适宜水平为8 mmol/L和NH4+/NO3->50/50。

The effects of four nitrogen（N） levels（1,4,8,and 16 mmol/L,using ammonium nitrate as the N source） and five NH＋4/NO-3 ratios（100/0,75/25,50/50,25/75,and 0/100） on the growth,N metabolism and photosynthesis of anther-derived somatic seedlings of Hevea brasiliensis were studied in a sand culture experiment.The dry weight of stem,leaves,shoot and single plant,the N concentration and N uptake of the roots,stem and leaves,and the chlorophyll concentration increased correspondingly with the increasing N level.The N concentration of the coarse roots,stem and leaves,N uptake by the plant,and the concentrations of chlorophyll a,chlorophyll b and total chlorophyll all differed significantly between treatments.The plant height,stem diameter,dry weight of fine roots and net photosynthetic rate of leaves increased with N level from 1 to 8 mmol/L,but decreased at 16 mmol/L.The nitrate reductase activity of fine roots was highest at the lowest N level.With regard to the effects of NH＋4/NO-3 ratio,the N concentration and N uptake in different parts of seedlings were highest when grown exclusively with NH＋4 nutrition（except N uptake of fine roots and petioles）;plant height,stem diameter,and the dry weights of the petioles,leaves,shoot and plant were highest in the 75/25 NH＋4/NO-3 treatment;the dry weight of the fine roots and stem,the chlorophyll concentration and the net leaf photosynthetic rate were highest in the 50/50 NH＋4/NO-3 treatment,and all were significantly higher than those of seedlings grown exclusively with NO-3 nutrition but were not significantly different from those of the treatments with 50/50 NH＋4/NO-3 ratios except the N concentration of the fine roots and stem.Nitrate reductase activity of fine roots was highest with NO-3 nutrition,but growth of the seedlings was weakest in this treatment.The results indicated that growth of the anther-derived somatic seedlings of Hevea brasiliensis was superior with NH＋4 alone or combined NH＋4/NO-3 nutrition rather than NO-3 nutrition alone,and the optimal N level was 8 mmol/L with a NH＋4/NO-3 ratio exceeding 50/50.