Ionic balance, proton efflux, nitrate reductase activity and growth ofHippophaë rhamnoides L. ssp.rhamnoides as influenced by combined-N nutrition or N2 fixation

Abstract

Growth of 2-month-old nonnodulated Hippopha~ rhamnoides seedlings supplied with combined N was compared with that of nodulated seedlings grown on zero N. Plant growth was significantly better with combined N than with N2 fixation and, although not statistically significant for individual harvests, tended to be highest in the presence of NH~, a mixture of NH~ and NO3 producing the highest yields. Growth was severely reduced when solely dependent on N: fixation and, unlike the combined-N plants, shoot to root ratios had only slightly increased after an initial decrease. An apparently insufficient nodule mass (nodule weight ratio < 5 per cent) during the greater part of the experimental period is suggested as the main cause of the growth reduction in N2-fixing plants.The in vivo nitrate reductase activity (NRA) of NO 3 dependent plants was almost entirely located in the roots. However, when grown with a combination of NO; and NH2, root NRA was decreased by approxi- 'Without acidity control and in the presence of NH4 +, specific rates of ion uptake and carboxylate generation were strongly depressed and growth was reduced by 30-35 per cent. Growth of nonnodulated H.rhamnoides plants ceased at the lower pH limit of 3.1-3.2 and deterioration set in; in the case of N2-fixing plants the nutrient solution pH stabilized at a value of 3.8-3.9 without any apparent adverse effects upon plant performance.The chemical composition of experimental and field-growing plants is being compared and some comments are made on the nitrogen supply characteristics of their natural sites.

Effects of the expansion by Hippophaë rhamnoides on plant species richness in coastal dunes

“…In humid regions the higher content of litter and organic matter in the soil beneath the shrubs allows more water to be retained in the soil (Hodgkin 1984). The decomposition of litter and organic matter as well as the leaching of calcium and other base cations in older dunes may cause a decrease in soil pH (Oremus & Otten 1981;Rozema et al 1985;Troelstra et al 1987). In our study, however, a lower pH in the shrubland plots was only observed on Norderney.…”

“…With an increasing cover of shrubs, the leaf litter accumulates in low-fertility sites such as dunes which results in a gradual carbon and nutrient enrichment of the soil (Hopkins 1996). High nitrogen contents of soils in dense stands of Hippophaë rhamnoides were reported by Pearson & Rogers (1962), and older stands were found to have twice the amount of nitrogen than young stands (Oremus & Otten 1981;Troelstra et al 1987). In a related study of the N-fixing species Porlieria chilensis shrubland in coastal Chile, the levels of soil nitrogen, phosphorus and organic matter were higher beneath the shrubs than in the surrounding area (Gutiérrez et al 1993).…”

Temporal and spatial variability in soil nutrient status of a former beach plain

“…comm. ), and N, P, and K concentrations of about 1600 mmol kg -1, 50 meq kg -1, and 200 meq kg -1 dry matter, respectively (Troelstra et al, 1987), this corresponds with about 56 g N m -2, 4 g P m -2, and 0.5 Eq K m -2.…”

Nodulation and nitrogen accretion response of Cercocarpus betuloides seedlings to phosphorus supplementation and water availability

“…Actinorhizal plants are not solely dependent on N-fixation to fulfill their nutritional needs for N. Some amount of inorganic-N is required to meet plant needs prior to the establishment of effective nodules and a lack of inorganic-N during the seedling stage of plant development has been show to reduce growth, nodulation and N-fixation in actinorhizal shrubs (Mackay et al, 1987;Troelstra et al, 1987). While N-accretion by seedlings in the control treatment (Table 3) was inflated by the single seedling which developed a nodule, this value (7.9 + / -1.45 mg pot -1) is close to the value predicted when acetylene reduction is zero (Y-intercept, Fig.…”