Irrigation effects on the growth, yield, and water use efficiency of alfalfa

A field study was conducted in the semiarid region of northern Sudan to investigate the effects of variable irrigation on the growth, yield, and water use efficiency (WUE) of alfalfa (Medicago sativa L.). Treatments were 65 mm of water applied every 7 days, 80 mm of water applied every 10 days, or 104 mm of water applied every 13 days. The heavy, infrequent irrigation reduced stem height, stem density, leaf area index (LAI), total biomass production, and the WUE of alfalfa plants. Maximum yields for six harvests were 15.3, 12.9, and 11.2 ton ha^–1 and the WUE values were 0.12, 0.10, and 0.08 ton ha^–1 cm^–1 for the frequent, less-frequent, and infrequent irrigation regimes, respectively. In all the treatments, alfalfa dry matter yield was positively correlated with stem height and LAI. The relationship between dry matter yield and total water use was a linear function (R ²=0.99), regardless of the irrigation treatment. Alfalfa growth, yield, and WUE remained high during the relatively cool months and declined during the hot period under the three water regimes. It was concluded that alfalfa grown under semiarid conditions should be watered lightly and frequently to attain high yields and high WUE. Received: 19 February 1996     

Identification of immunogenic proteins associated with protection against haemorrhagic septicaemia after vaccination of calves with a live-attenuated aroA derivative of Pasteurella multocida B:2

Pasteurella multocida serotype B:2 is the causative agent of haemorrhagic septicaemia (HS), a fatal disease of cattle and buffaloes. As a step towards the identification of individual antigens that may protect against HS, proteins present in a sonicated cell extract (SCE) and outer-membrane protein (OMP) preparation of a wild-type P. multocida serotype B:2 were investigated by immunoblotting with sera from calves which had been protected against challenge with a virulent strain of P. multocida B:2 by vaccination with a live-attenuated aroA derivative of the challenge strain. Five proteins in SCE, of approximately 50, 37, 30, 26 and 16 kDa, were recognised by the sera. In an OMP preparation, two bands, at 37 and 50 kDa, were recognised as strongly immunogenic. Mass spectrometry analysis of proteins corresponding in size to those detected by immunoblotting identified the 37 kDa band as OmpA, but the band at 50 kDa was not identified with certainty. A major 30 kDa OMP, identified as OmpH, was not strongly immunogenic.     

Ultrastructure features of camel cornea--collagen fibril and proteoglycans

Introduction The uniform distribution of collagen fibrils and proteoglycans maintain the transparency of normal cornea. We describe the ultrastructural features of camel cornea including collagen fibrils and proteoglycans (PGs). Methods Camel corneas (of 6‐, 8‐, and 10‐month‐old animals) were fixed in 2.5% glutaraldehyde containing cuprolinic blue in sodium acetate buffer and processed for electron microscopy. The ‘AnalySIS LS Professional’ program was used to analyze the collagen fibril diameter. Results The camel cornea consists of four layers: the epithelium (227 μm), stroma (388 μm), Descemet’s membrane (DM), and endothelium. The epithelium constituted 36% of the camel cornea, whereas corneal stroma constituted 62% of the corneal thickness (629 μm). The PGs in the posterior stroma were significantly larger in number and size compared with the anterior and middle stroma. The collagen fibril diameter was 25 nm and interfibrillar spacing 40 nm. Fibrillar structures are present throughout the DM. Conclusion The structure of the camel cornea is very different from human and other animals. The unique structure of the cornea might be an adaptation to help the camel to survive in a hot and dry climate. The camel cornea may also be a good model to study the effect of hot and dry climates on the cornea.     

Growth-related changes in wheat (Triticum aestivum L.) genotypes grown under salinity stress

The sensitivity of crop genotypes determines the level of growth reduction by salinity. Effect of salinity levels (7.5 and 15 dihydrate m^?1) using completely randomized design (CRD) with four replications per treatment were compared on germination, chlorophyll content, water potential, ionic sodium and potassium (Na⁺, K⁺) balance, and other growth-related parameters of six wheat genotypes for varietal differences under long-term salinity stress. Chlorophyll contents at flowering stage and yield aspects at maturity of all the wheat genotypes decreased with increasing salinity. The maximum Na⁺ concentration was observed at 7.5 and 15 dS m^?1 in Bhakhar and Saher-2000, respectively, while minimum Na⁺ concentration was observed for 9476. However, the maximum K⁺ concentration and water potential was noticed in 9476 at 7.5 dS m^?1. Careful selection of salt-tolerant genotypes for field crops is an important perspective especially in the developing countries facing salinity problem. Our results revealed that the wheat genotype 9476 performed best regarding growth and physiological parameters compared to other wheat genotypes.