Hamdi Y, Yousef A N
Zentralbl Bakteriol Naturwiss. 1979;134(1):19-24. doi: 10.1016/s0323-6056(79)80059-2.
Six species of common desert range plants; Achillea sp., Aristida plumosa, Artemisia herba-alba, Haloxylon articulatum, and Heliotropium ramosissimum were colleted from Western Desert in Iraq. Counts of Azotobacter spp. and total bacteria were estimated in both rhizosphere and non-rhizosphere soils. Biomass and total nitrogen content of the plants were determined. The R/N ratio (ratio between rhizosphere to non-rhizosphere) for Azotobacter sp. ranged between 1 to 19.5 with an average of 4.96. The number of Azotobacter in the rhizosphere ranged between 6.8 X 10(3) to 47 X 10(3) cells/g, while in the non-rhizosphere it ranged from 2 X 10(3) to 21 X 10(3). Aristida plumosa harboured the highest number, i.e., 47 X 10(3) cells/g, while Artemisia herba-alba showed the least, i.e., 6.8 X 10(3) cells/g. Total counts of bacteria in the rhizosphere ranged between 17.2 X 10(6) and 97 X 10(6) cells/g, that of the non-rhizosphere between 1.5 X 10(6) and 18 X 10(6) cells/g. The R/N ratio ranged between 2.03 X 22.5 with an average of 7.28. An appreciable gain of dry weight and total nitrogen was observed. Between 13 and 152 g with an average of 78.9 g dry weight and between 347 and 6684.0 mg with an average of 2452.0 mg nitrogen per plant were found. The possible contribution of Azotobacter to the nitrogen economy of the plants is discussed and further suggested.
蓍属植物、羽状三芒草、白蒿、盐生假木贼和多枝天芥菜。对根际土壤和非根际土壤中的固氮菌属和总细菌进行了计数。测定了植物的生物量和总氮含量。固氮菌属的根际与非根际比值（R/N比）在1至19.5之间，平均为4.96。根际固氮菌数量在6.8×10³至47×10³个细胞/克之间，而非根际则在2×10³至21×10³个细胞/克之间。羽状三芒草的固氮菌数量最多，即47×10³个细胞/克，而白蒿的数量最少，即6.8×10³个细胞/克。根际细菌总数在17.2×10⁶至97×10⁶个细胞/克之间，非根际在1.5×10⁶至18×10⁶个细胞/克之间。R/N比在2.03至22.5之间，平均为7.28。观察到干重和总氮有明显增加。每株植物的干重为13至152克，平均为78.9克，氮含量为347至6684.0毫克，平均为2452.0毫克。讨论并进一步提出了固氮菌对植物氮素营养的可能贡献。
