Effect Of N Input On Above-and Belowground Morphological And Physiological Characteristics Of Bothriochloa Ischaemun

A pot experiment was used to study the effect of N addition on the above and below-ground morphological and physiological characteristics of Bothriochloa ischaemun. The six nitrogen treatments were:0(CK),0.02(N1),0.04(N2),0.08(N3),0.16(N4) and0.32g/kg(N5), and we got the main conclusions as follows:1. There were significant effects of N addition on above-ground morphological characteristics of Bothriochloa ischaemun. With the soil N concentration increased, the mean height, biomass and leaf area decreased, while the tiller number increased, reached maximum in0.04g/kg treatment(21.8/plant);2. Effect of N addition on photosynthetic characteristics of Bothriochloa ischaemun: With the enhancement of photosynthetic active radiation (0-2000μmol.m-2·s-1), the photosynthetic rate increased in all the N treatments, and the maximum net photosynthetic rate increased with the increasing N concentration,0.04g/kg treatment had the maximum net photosynthetic rate. The results showed that diurnal change in net photosynthetic rate (Pn) of Bothriochloa ischaemun leaves was a bimodal curve determinately regulated by non stomatal factors.3. Effect of N addition on root morphological of Bothriochloa ischaemun:(1) the mean fine root diameter and mean root length tended to increase (P<0.05) with ascending root orders, while specific root length (SRL) and total root length decreased (P<0.05);(2) the mean root diameter, mean root length increased with increasing N fertilization, however, the SRL, total root length and root mass decrease with increasing N fertilization, except the diameter of the1st order root.(3) N fertilization increased the root extension rate (RER) and increased radial growth rate (RGR). And the RER s and RGRs for all the four order roots increased to the peak at first, followed by decreasing, and then kept constant, and the1st and2nd order roots were the most sensitive to the increase in soil N availability.4. Effect of N addition on fine root production and turnover of Bothriochloa ischaemun: With increasing nitrogen concentration, the fine root production (RLDp) of Bothriochloa first increased, reached to the maximum in0.04g/kg treatment, then decreases with increasing nitrogen level, but apart from0.04g/kg treatment, as well as certain treatments, there was no significant differences among the rest of the N treatment (p>0.05).The mean fine root production tended to increase (P<0.05) with ascending root orders, while the root turnover decreased (P<0.05). The root turnover of1st root order (5.08-6.44a-1) was much lager than the other three root orders, N addition increased the turnover of1st-2nd, while have no significant effect on3rd-4th root orders (p>0.05).5. N addition significantly reduce the root/shoot ratio, the minimum occurred in N3treatment, and had significant difference with the other treatments. N application reduced the relative proportion of roots carbon allocation.