/pdf/laboratory-manual-for-physiological-studies-of-rice-37e0a0qv1v.pdf

Laboratory manual for physiological studies of rice

Biological and Phytochemical Screening of Plants

In order to determine the relative importance of ionic toxicity versus the osmotic component of salt stress on germination in durum wheat (Triticum durum Desf.), seeds of three cultivars differing in their salt and drought resistance (Omrabi-5, drought-resistant; Belikh, salt-resistant and Cando, salt-sensitive) were incubated in various iso-osmotic solutions of NaCl, mannitol and polyethylene-glycol (PEG) (osmotic potential of −0.15 (control solution) −0.58, −1.05 or −1.57 MPa). Moderate stress intensities only delayed germination, whereas the highest concentration of NaCl and PEG reduced final germination percentages. PEG was the most detrimental solute, while mannitol had no effect on final germination percentages. All osmotica reduced endosperm starch and soluble sugars content as well as α-amylase activities recorded after 48 h of treatment while β-amylase activities were, in contrast, slightly stimulated in all cultivars. Deleterious effects of NaCl and PEG were higher on isolated embryos germinated onto an in vitro Linsmaier and Skoog (LS) medium comparatively to whole seeds. All PEG-treated embryos, however, recovered after the stress relief while NaCl-treated embryos exhibited a lower rate of recovery and some extent of abnormal germination after rinsing. It was concluded that stress inhibition of germination could not be attributed to an inhibition of mobilisation of reserves and that the main effect of PEG occurred via an inhibition of water uptake while detrimental effects of NaCl may be linked to long-term effects of accumulated toxic ions. The behaviour of the three cultivars during germination did not fully reflect their mean level of putative stress resistance in field conditions and germination is, therefore, not recommended as a reliable selection criterion for breeding purposes.

Effect of salt and osmotic stresses on germination in durum wheat (Triticum durum Desf.)

Publisher Summary This chapter presents a procedure for the determination of glycogen and starch. Determination of glycogen by the modified Pfluger method consist digestion of the tissue in hot concentrated KOH, precipitation of the glycogen with ethanol, hydrolysis of the glycogen with acid, and determination of the glucose in the hydrolyzate as reducing sugar. Determination of glycogen with anthrone reagent includes digestion with 30% KOH. The glycogen is treated with the anthrone reagent and determined colorimetrically as glucose. Determination of glycogen in tissues of low glycogen content include digestion by boiling water and 1.25 ml. of 95 % ethanol is added for centrifugation. The glycogen is hydrolyzed by the addition of 1 ml. of 0.6 N HC1 for 20 minutes. The sugar is determined by any of the standard methods for microdetermination of sugars. The principle of determination of starch states that starch can be determined as glucose when extracted from dried plant tissue treated with perchloric acid, precipitated with iodine, and hydrolyzed with acids. Starch or glycogen determined by methylation technique.

[7] Chemical procedures for analysis of polysaccharides

A colorimetric method using anthrone is described for the estimation of starch and soluble sugars in cereals, cereal by-products, and mixed poultry rations. The method is rapid and requires no elaborate apparatus. An internal glucose standard is used. Results for the starch content of these materials show a standard deviation of 2–2% of the mean value.

R. M. McCready

Papers

Determination of Starch and Amylose in Vegetables