2 results
Assessment of sulphur deficiency in commercial oilseed rape crops from plant analysis
- X. SARDA, S. DIQUELOU, M. ABDALLAH, N. NESI, O. CANTAT, P. LE GOUEE, J. C. AVICE, A. OURRY
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- Journal:
- The Journal of Agricultural Science / Volume 152 / Issue 4 / August 2014
- Published online by Cambridge University Press:
- 01 March 2013, pp. 616-633
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Sulphur (S) is one of the six main macroelements required to sustain the growth of plants. Sources include soil, fertilizer and atmospheric deposition, which has been reduced by 85% over the last three decades. Risks of S deficiencies are now recognized in high S-demanding species such as Brassica napus L. With the aims of evaluating the risk of excessive or insufficient fertilization and identifying robust relationships that may be used as plant S status indicators, 57 commercial crops of oilseed rape were selected among contrasting soils and along a rainfall gradient that may affect soil S availability. Cultivation practices were investigated and the S and nitrogen (N) concentrations of soil, senescing leaves, stems and seeds were analysed. Despite an excessive organic N supply and large variation in S supply (from 0 to 112 kg S/ha), principal component analysis using 43 parameters indicated that seed yield was poorly related to N and S fertilization rates. While the N and protein-N concentrations in seeds were inversely related to oil and glucosinolate concentrations, they were linked to S and sulphate (SO42−) accumulation in the seeds. Sulphate concentrations in senescing leaves, stems or seeds could be deduced from total S concentrations, as they were positively and highly correlated. Sulphate accounted for on average 0·69 of total S in senescing leaves with minimum and maximum values of 0·007 and 0·94, which revealed conditions of limited and excess supply of S, respectively. This high variation of SO42− concentration in leaves can be interpreted as the result of its mobilization triggered by S deficiency, but cannot be used alone as an indicator of plant S status. A comparison with plants grown in controlled conditions under different S supplies suggests that the intensity of S starvation affects N metabolism, leading to NO3− (nitrate) accumulation. It is further suggested that dual evaluation of SO42− and NO3− concentrations in senescing leaves could be used at the vegetative stage as a field indicator to adjust S fertilization.
Spent females of deepwater squid Galiteuthis glacialis under the ice at the surface of the Weddell Sea (Antarctic)
- K. N. Nesis, Ch. M. Nigmatullin, I. V. Nikitina
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- Journal:
- Journal of Zoology / Volume 244 / Issue 2 / February 1998
- Published online by Cambridge University Press:
- 01 February 1998, pp. 185-200
- Print publication:
- February 1998
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Two large (dorsal mantle length 42.5 and 47.5 cm), mated spent females of circum-Antarctic bathypelagic cranchiid squid Galiteuthis glacialis were caught early in March 1992 at the surface of the ice hole in the western Weddell Sea over depths 1915-1920 m by the team of the U.S.A.-Russian Ice Station Weddell-I. The structure of the reproductive system of adult females is described for the first time in detail.
Both were gelatinous, devoid of tentacles, with empty or almost empty stomachs. The empty spermatangia (sperm reservoirs of spermatophores) 30-35 mm in length were distributed in the mantle tissues parallel to the mantle surface and to each other in the dorso-anterior part of the mantle: 13 in one female, parallel to the body axis, and 20 in the other, parallel (13) or perpendicular (7) to the body axis. In the latter case, they represented probably two mating events. The spermatangia lay nearer to the inner than the outer mantle side and opened by a round window on the inner side; the skin with chromatophores above them remained intact. The spermatozoa had one flagellum and rod-like heads, length 5.0-5.3 μm, width 1.2-1.5 μm. The most characteristic features are: a very simple type of blood vessel branching making each micro-gonad currant-like, not grape-like; a very compact disposition of oviducal, nidamental glands and gill, forming a united complex located on both sides of the mantle cavity; and an ovary connected by mesentery along all its length with the continuation of the stomach from the caecum to the end of the gastrogenital ligament. Only immature degenerating trophoplasmatic oocytes, length 0.9-1.4, av. 1.0-1.2 mm, were contained in ovaries; only one mature egg (length 3.3 mm, width 2.4-2.5 mm) was found in each female. The absence of oocytes <0.9 mm and 1.5-3.2 mm indicates that the maturation of oocytes proceeds rather synchronously, one large portion of eggs (some tens of thousands) matures in a short time while others degenerate. The residual fecundity is assessed to be approximately 20,000 eggs.
It is hypothesized that mating occurs shortly before spawning and that mature males do not undergo gelatinous degeneration and do not lose tentacles. Spermatophores are placed on the inner side of the female's mantle with the aid of the male's tentacles and/or arms (less probably by the penis), but the exact mode of implantation is unclear. Spawning probably occurs at depths of adult habitat (approx. 500±2500m), may be multiportional but short; the exhausted female loses neutral buoyancy, rises to the surface and dies. Rising to the surface after spawning is a common feature of females of many meso- and bathypelagic squids undergoing gelatinous degeneration during maturation (Onychoteuthidae, Gonatidae, Histio-teuthidae, Cranchiidae, etc.) and may explain the common occurrence of large deep-water squids in the stomachs of seabirds, including those incapable of diving, and marine mammals.