Changes in the activity of acid phosphatase (AcPase) in the apoplast of pea root nodule were investigated. The activity was determined using lead and cerium methods. The results indicated a following sequence of AcPase activity appearance during the development of the infection thread: 1) low AcPase activity appears in the outer part of cells of symbiotic bacteria; 2) bacteria show increased AcPase activity, and the enzyme activity appears in the thread walls; 3) activity exhibits also matrix of the infection thread; 4) bacteria just before their release from the infection threads show high AcPase activity; 5) AcPase activity ceases after bacteria transformation into bacteroids. The increase in bacterial AcPase activity may reflect a higher demand for inorganic phosphorus necessary for propagation of the bacteria within the infection threads and/or involved in bacteria release from the infection threads.
ACPase activity was localized in the apoplast of pea root nodules under phosphorus deficiency. Pea plants (Pisum sativum L. cv. Sześciotygodniowy) where inoculated with Rhizobium leguminosarum bv. viciae 248 and were cultured on nitrogen-free medium with phosphate (-N/+P) or phosphate-deficient (-N/-P) one. In comparison with control nodules, P-deficient nodules showed the increase of ACPase activity in plant cell walls and the infection threads. The increase in bacterial ACPase activtty under P-deficiency may reflect higher det mand for inorganic phosphorus that is necessary for bacteria multiplication within the infection threads. The increase of ACPase activity in nodule apoplast under P stress may enlarge the availability of phosphate for plant and bacteria.
Observations were conducted over 5 years (1989-1993) in natural stands in southeastern Poland. The aim of this research was to examine relations between Sitona weevils and wild- growing leguminous plants. In total, 28861 weevils (Citrculionidae) were collected from which 10425 (36.1%) belonged to the Sitona genus. The most common species was lineatus L., which was collected in each examined stand. Adult forms of this weevil occurred in large numbers especially on Vicia sp.. S. humeralis Steph. was dominant on Medicago sativa, S. cylindricollis Fahrs. grew on Melilotus albus, S. sulcifrons Thunbg. was numerous on Trifolium pratense and T. alpestre. S. waterhousei Walt, occurred on Lotus corniculatus whereas S. suturalis Steph. was dominant on Lathyrus pratensis. Coronilla varia was dominated by S. languidus Gyll. and Ononis arvensis was dominated by S. suturalis. So, we can say that every leguminous plant is accompanied by at least one specialised Sitona species, which can essentially reduce the number of root nodules and consequently decreased the quantity of fixed atmospheric nitrogen in soil.
Ultra-structural studies were conducted on root nodules of Samanea saman (Jacq.) Merr. collected from trees growing under natural conditions. Nodules were distributed singly as well as in clusters on the main and lateral roots. Mature nodules were elongated, branched and coralloid. Root hair curling was found but infection threads could not be observed. Rhizobia entered through the epidermis and moved intercellularly through the cortical region. Mature nodules of S. saman could be differentiated into meristem, cortex, vascular tissue and bacteroid tissue. The latter showed both infected and non-infected cells mixed together. Vascular bundles were inversely collateral and distributed around the bacteroid tissue. The bacteroids were enclosed in peribacteroid membrane in groups and showed prominent granules of polyhydroxybutyrate in their cytoplasm. Mycorrhizal hyphae were also observed along with rhizobia in the bacteroid tissue. S. saman with dual rhizobial and mycorrhizal infection is a potential tree for plantation in arid soils of Pakistan.
A gene for the Δ9 desaturase specific to stearoyl-ACP (acyl carrier protein) was identified from yellow lupine (Lupinus luteus) cDNA and genomic libraries through the differential display method. The desaturase transcript appears in plants infected with Bradyrhizobium sp. (Lupinus) as revealed by Northern hybridization, RT-PCR and expression of β-glucuronidase under the desaturase promoter. A small amount of desaturase transcript was also detected in uninfected plants, which suggests that the gene does not belong to the strict nodule-specific sequences. The desaturase provides unsaturated fatty acids for additional cell membrane synthesis. During nodule and symbiosome development a peribacteroid membrane is formed and the requirement for membrane surface increases, thus the level of desaturase expression is also higher. Transgenic plants of Nicotiana tabacum with overexpression of the full-length lupine stearoyl-ACP desaturase sequence were obtained. They revealed higher content of unsaturated fatty acids (especially oleic acid) in comparison with control plants.
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