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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Nutrient cycling in agroecosystems 20 (1989), S. 83-88 
    ISSN: 1573-0867
    Keywords: Phosphate uptake ; immobilization of phosphate ; banding ; broadcasting ; root length ; root distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The authors demonstrated in part I that phosphate banded with the seeds of durum wheat (Triticum vulgare), L., cv. Sham 1) was generally superior to broadcasting in improving P uptake, especially at early growth. These results were confirmed for three consecutive seasons at three experimental sites with calcareous soils in Northern Syria (mean annual rainfall 281–471 mm). Two mechanisms have been postulated by various authors to explain the advantageous effect of banding on P fertilizer use efficiency: i) banding reduces soil to fertilizer contact resulting in less immobilization of P by fixation in the calcareous soils and ii) banding increases the root to P fertilizer contact and concentration, resulting in greater P uptake. The present work was designed to test these two hypotheses by measuring within the surface 20 cm of soil, i) the effect of method (banding vs. broadcasting) of P application (0, 17.5 and 52.5 kg P ha−1 as triple superphosphate) on the change of NaHCO3-extractable P with time and ii) the length and distribution of roots at tillering in relation to the distribution of available P in the soil. It was found that: i) The reduction in P availability with time was independent of the method of P placement and the residual NaHCO3-P one year after its application was practically the same (for the same rate of P, whether banded or broadcast; and ii) the growth of roots was increased in the volumes of soil containing the P fertilizer, particularly where P was banded. It was concluded that, for wheat grown in calcareous soils in a Mediterranean climate, the greater uptake of P by crops where the fertilizer was banded was due to an increased probability of contact between roots and P fertilizer granules.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1615-6102
    Keywords: Cell cycle ; Protoplast division ; Chromatin structure ; Flow-cytometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Using different sources of protoplasts and two complementary techniques, flow cytometry and image analysis, to study the cell-cycle phases, we sought to define the particular protoplast state associated with the disposition to divide. Both inPetunia and inNicotiana plumbaginifolia, tissues with a higher G2 frequency (from different aged plants) yielded protoplasts capable of increased cell division. InSorghum, the age of the plant does not modify the proportion of G2 nuclei in leaf protoplasts, and we used root protoplasts to increase G2 frequencies. InHelianthus annuus, leaf protoplasts did not divide; however, hypocotyl protoplast preparations with relatively high 4C DNA frequencies do divide. Moreover, image analysis of chromatin structure indicated that leaf nuclei were in the G0 phase, unlike those from hypocotyls which were in G1. A high frequency of protoplasts with G2 nuclei appears to be correlated with the ability of a given preparation to undergo division; conversely, the differentiated G0 state is not conducive to division.
    Type of Medium: Electronic Resource
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