Salinity Tolerance in Brassica Oilseeds

Brassica oilseed species now hold the third position among oilseed crops and are an important source of vegetable oil. The most common Brassica oil-seed crops grown for commercial purposes are rape seeds, (Brassica campestris L. and B. napus L.) and mustards (B. juncea (L.) Czern. & Coss. and B. carinata A.Br.). The other Brassica species such as B. nigra (L.) Koch and B. tournefortii Gouan are grown on a very small scale. Brassica napus, B. juncea, and B. carinata are amphidiploids, whereas B. campestris and B. nigra are diploid. Most of the Brassica species have been categorized as moderately salt tolerant, with the amphidiploid species being the relatively salt tolerant in comparison with the diploid species. Due to the higher salt tolerance of the amphidiploids, it has been suggested that their salt tolerance has been acquired from the A (B. campestris) and C (B. oleracea L.) genomes. However, significant inter- and intraspecific variation for salt tolerance exists within brassicas, which can be exploited through selection and breeding for enhancing salt tolerance of the crops. There are contrasting reports regarding the response of these species to salinity at different plant developmental stages, but in most of them it is evident that they maintain their degree of salt tolerance consistently throughout the plant ontogeny. The pattern of uptake and accumulation of toxic ions (Na⁺ and Cl^?), in tissues of plants subjected to saline conditions appears to be mostly due to mechanism of partial ion exclusion (exclusion of Na⁺ and/or Cl^?) in most of the species, although ion inclusion in some cases at intraspecific levels has also been observed. Maintenance of high tissue K⁺/Na⁺ and Ca^{2 +}/Na⁺ ratios has been suggested as an important selection criterion for salt-tolerance in brassicas. Osmotic adjustment has also been reported in Brassica plants subjected to saline conditions, but particularly to a large extent in salt-tolerant species or cultivars. The roles of important organic osmotica such as total soluble sugars, free amino acids, and free proline, which are central to osmotic adjustment, have been discussed. In canola, B. napus, no positive relationship has been observed between salt tolerance and erucic acid content of seed oil in different cultivars. Furthermore, glucosinolate content of the seed meal in canola generally increases with an increase in salt level of the growth medium. This review highlights the responses of potential Brassica crops to soil salinity from the whole plant to the molecular level. It also describes the efforts made during the past millennium in uncovering the mechanism(s) of salinity tolerance of these crops both at the whole plant and cellular levels. The important selection criteria, which are used by researchers to enhance the degree of salinity tolerance in brassicas, are summarized. In addition, the vital role of genetic engineering and molecular biology approaches to the improvement of salt tolerance in brassicas is emphasized.     

Suppression of plasma FSH concentrations with bovine follicular fluid blocks ovulation in GnRH-treated seasonally anoestrous ewes

The specific requirement for FSH in the final stages of preovulatory follicle development was assessed in seasonally anoestrous ewes given 2-h injections of GnRH (250 ng/injection), with (N = 10) or without (N = 10) concurrent treatment with bovine follicular fluid (bFF: 2 ml given i.v. at 8-h intervals). Treatment with bFF significantly (P less than 0.01) suppressed plasma FSH concentrations, but, at least for the first 30 h of treatment, did not influence the magnitude of GnRH-induced LH episodes (mean max. conc. 3.00 +/- 0.39 and 3.63 +/- 0.51 ng/ml for bFF-treated and control ewes, respectively). Of 10 animals treated with GnRH for 72 h, 5/5 control ewes showed oestrus and ovulated whereas 0/5 bFF-treated ewes showed oestrus or ovulated in response to GnRH treatment. There was, however, a transient (13.2 +/- 1.0 h) increase in plasma LH concentrations in the ewes given bFF (mean max. conc. 4.64 +/- 1.57 ng/ml), which was coincident with the preovulatory LH surge recorded in animals given GnRH alone. In 10 GnRH-treated ewes slaughtered after 32 h of treatment, the mean diameter of the largest antral follicle was significantly (P less than 0.001) greater in control ewes (5.92 +/- 0.17 mm) than in animals that were also given bFF (3.94 +/- 0.14 mm). In addition, the incidence of atresia in the 3 largest antral follicles present at this time was greater in bFF-treated ewes. These results show that, when plasma FSH concentrations are suppressed by administration of bFF, although the magnitude of GnRH-induced LH episodes is unchanged, preovulatory follicular development is impaired and ovulation does not occur.(ABSTRACT TRUNCATED AT 250 WORDS)     

Observer Variation in the Clinical and Radiological Assessment of Hepatosplenomegaly

The size of the liver and spleen of 32 patients was assessed by four clinicians from a clinical examination and by four radiologists from a plain radiograph of the abdomen. The latter assessment was found to be subject to less variation than the former, particularly in regard to the liver. Large livers and spleens were more easily seen radiologically than small ones. Most of the variation among the radiologists arose because of the 6% and 24% of cases in which the liver and spleen, respectively, were poorly seen on the radiograph. It is concluded that a plain radiograph of the abdomen, including the diaphragm and with the costal margin indicated, is a useful adjunct to clinical examination.     

Suppression of follicular development after chronic LHRH immunoneutralization in the ewe

Active immunization of 6 Damline ewes against LHRH during seasonal anoestrus resulted in an inhibition of ovarian cyclicity throughout 2 subsequent breeding seasons. This was associated with a significant suppression of plasma LH and FSH concentrations but no significant effect on prolactin. The ovaries of LHRH-immunized ewes 30 months after primary immunization contained no follicles greater than 2.5 mm in diameter and a greater proportion of follicles between 1 and 2 mm were atretic than in control ewes (N = 8). In-vitro production of testosterone and androstenedione were similar in follicles 1-2 mm in both control and LHRH-immunized ewes (N = 6) and all had little or no ability to secrete oestradiol. However, basal and hCG-stimulated progesterone secretion was suppressed in the follicles from LHRH-immunized ewes. These results show that follicular development beyond 2.5 mm in the ewe is dependent on adequate stimulation by both LH and FSH.     

Release of oxytocin and prolactin in response to suckling.

The oxytocin and prolactin responses to suckling were measured in 10 women in early (n = 5) and established lactation (n = 5). Oxytocin was released in a pulsatile manner during suckling in all women, but the response was not related to milk volume, prolactin response, or parity of the mother. In all 10 women plasma oxytocin concentrations increased three to 10 minutes before suckling began. In five women this occurred in response to the baby crying, in three it coincided with the baby becoming restless in expectation of the feed, while in two it corresponded with the mother preparing for the feed. There was no prolactin response to stimuli other than stimulation of the nipple associated with suckling. These results clearly indicate that the milk ejection reflex, with release of oxytocin, occurs in most women before the tactile stimulus of suckling. A second release of oxytocin follows in response to the suckling stimulus itself. Thus it is important that care is taken to protect breast feeding mothers from stress not only during suckling but also immediately before nursing, when conditioned releases of oxytocin will occur.