Drought stress is often the most limiting factor for maize and sorghum production in the semi-arid areas. This study evaluates the enzymatic antioxidant protection mechanism response of maize (cv Melkassa-2) and sorghum (cv. Macia) after exposure to and recovery from pre- and post-flowering dehydration.The response of enzymatic antioxidant protection systems revealed that in both test crops dehydration during both the pre- and post-flowering stages resulted in increased activities of enzymatic antioxidant protection mechanisms (SOD, GR, CAT and APX). There were, however, differences between the species in the type and extent of enhanced developmentally-induced and dehydration-induced antioxidant activities. Differences were also noticed in the relative water contents at which changes in enzymatic antioxidant activities occurred. Under dehydration conditions, sorghum was generally found to have relatively higher enzymatic antioxidant activities, providing it better protection against oxidative stress by minimizing the level of lipid peroxidation.Lipid peroxidation, measured as MDA content, was increased in both species during pre- and post-flowering dehydration, but the increase was greater in maize than in sorghum during both developmental stages. Sorghum appeared to be able to reduce MDA on rehydration, but maize contained only 85% less MDA after rehydration as compared to the control following pre-flowering rehydration. During post-flowering rehydration, neither species was able to decrease the MDA content to the control level.The results indicated that tolerance to drought in sorghum is well associated with the consistent enhanced capacity of the enzymatic antioxidant system under both pre- and post-flowering dehydration conditions, and that the sensitivity of maize to drought is linearly correlated to the decreased capacity of the antioxidant system. It may be concluded that, since differences were observed between the species in the response of enzymatic antioxidants to pre- and post-flowering dehydration/rehydration, with sorghum exhibiting comparatively higher overall activities of enzymatic antioxidants and a lower level of MDA than maize during both pre- and post-flowering dehydration, selection based on these criteria may help in the development of genotypes tolerant to dehydration.
Investigations were made on the seed viability (standard germination test and vigour after accelerated ageing) and seed quality (starch, protein, lipid, sucrose, glucose and fructose) of seeds of maize (cv Melkassa-2) and sorghum (cv Macia) harvested from plants after exposure to and recovery from pre- and post-flowering dehydration. The objectives of the study were to achieve a better understanding of 1) the effects of water deficit during the pre- and post-flowering stages on the seed viability and food (storage reserves) quality, and 2) the effects of dehydration and rehydration cycles at critical growth stages on subsequent seed performance and production, which could lead to the development of cultivars more able to efficiently partition assimilates to the reproductive organs in the field. The experiment was conducted in a controlled environment growth chamber under constant environmental conditions (12/12 h day/night, 28–32/17°C day/night temperature, 60–80% RH and 1200–1400 μmol m
PPDF). The seed viability and vigour tests were done on air-dried seeds and the seed quality analysis on freeze-dried seeds of both species.The results of the standard germination test indicated that sorghum seeds harvested after both pre- and post-flowering dehydration were not affected by the treatment, while maize seeds had reduced % germination. Sorghum seeds harvested after post-flowering dehydration had significantly decreased vigour after accelerated ageing. Dehydration during both the pre- and post-flowering stages resulted in reduced contents of protein, lipid and soluble carbohydrates (sucrose, glucose and fructose) in both species as compared to the control seeds. The species differed in the extent to which these reserves were reduced.
ERECTA is an ancient family of leucine-rich repeat receptor-like kinases (RLKs) that coordinate growth and development of plant. TaERECTA, one copy of the ERECTA homologs in wheat, was isolated from bread wheat Chinese Spring. The Ser/Thr kinase of TaERECTA was expressed in E. coli after IPTG induction and confirmed by immunoblot. TaERECTA showed higher expression in younger organs with rapid development, as well as great expression in younger spikes at booting stage. Under exogenous application of gibberellin (GA3) and abscisic acid (ABA), and Mg2+ stress, the expression of TaERECTA was largely suppressed, whereas under exogenous application of indole acetic acid (IAA) and brassinolide (BR), and dehydration stress, its expression was initially suppressed and then up-regulated. Natural variation was apparent in the relative expression of TaERECTA among 9 different bread wheat lines, and its expression level was negatively correlated with the stomatal density. These results suggested that TaERECTA could be exploitable for manipulating agronomical traits important through regulating stomata density, with potential implication for bread wheat improvement.
Bakalova, S., Nikolova, A., Nedeva, D. (2004): Isoenzyme profiles of peroxidase, catalase and superoxide dismutase as affected by dehydration stress and ABA during germination of wheat seeds.
Bulg. J. Plant Physiol.
Authors:F.R. Assis, J. Pissarra, R.M.S.C. Morais, and A.M.M.B. Morais
Apple cubes were osmotically dehydrated with 40 °Bx sucrose and sorbitol solutions. Light microscopy was used to observe the microstructure of fresh and osmotically dehydrated samples. Peleg’s model could fit the experimental data and describe the mass transfer kinetics of water loss (WL) and solid gain (SG). The use the sorbitol as osmotic agent, the increase of temperature and concentration of the solution increased the WL during the osmotic dehydration. The average cellular parameters, area and perimeter (size), and circularity, elongation, roundness, and compactness (shape) of fresh samples were 14.28±6.65×103 μm2 and 0.486 mm, and 0.73, 1.56, 0.70, 0.83, respectively. The osmotically dehydrated samples presented a decrease in area, circularity, roundness and compactness and an increase in the elongation of the cells, and these changes were higher in samples treated with sorbitol.
Apples (Idared) were subjected to osmotic dehydration in: a) 50% solutions of fructooligosaccharides (FOS) at 40–70 °C (apple/solution 1/2), b) 50% solution of FOS at 40 °C using different amount of solution (apple-solution ratio from 1/2 to 1/5), c) 50–65% solution of FOS at 40 °C (apple/solution 1/4). The content of fructooligosaccharides in dried material was determined. An increase in temperature and amount of the hypertonic solution intensified the migration of fructooligosaccharides to the fruit tissue. There was no direct relationship between the concentration of the hypertonic solution and the FOS content of dehydrated apples. the contents of fructooligosaccharides and dry substance in fruits dehydrated under different conditions were interlinked. Dehydrated apples of a content of fructooligosaccharides of 7–9% w/w were obtained when the content of dry substance was approximately 30%.
Authors:Bekim Gashi, Efigjeni Kongjika, Mirsade Osmani, and Valon Luma
Ramonda nathaliae and Ramonda serbica are resurrection plants belonging to homoiochlorophyllous desiccation-tolerant angiosperms. Chlorophyll biosynthesis is one of the most important metabolic pathways to tolerate desiccation in these plant species.
Materials and methods
To better understand the early pathway steps of chlorophyll biosynthesis, we have analyzed the enzyme δ-aminolevulinic acid dehydratase (ALA-D) and contents of δ-aminolevulinic acid (ALA) and total chlorophyll as a final product during dehydration and rehydration stages for these plant species.
Our results showed that the activity of ALA-D in R. nathaliae and R. serbica plants rapidly decreased during dehydration and in the final stage of desiccation the activity of this enzyme was decreased by 79% and 86%, respectively. After rehydration of plants, the ALA-D activity was fully restored. In contrast, the ALA content of both plant species significantly increased during desiccation and decreased after 48 hr of rewatering. In each stage of dehydration or rehydration, a significant negative correlation was established between ALA-D activity and ALA content in both plant species.
Total chlorophyll content was preserved more in R. nathaliae than in R. serbica during desiccation. Moreover, ALA-D activity was decreased to a minimal level but preserved its function during desiccation, and this suggests one possible mechanism of desiccation tolerance to retain the chlorophyll of these plant species.
In a 120 min osmotic dehydration procedure followed by an air drying process, the effect of carboxy-methyl cellulose (CMC) on some qualitative characteristics of apple slabs including browning index (BI) and rehydration capacity were studied. Moreover, the relation between textural and sensory properties, such as hardness, cohesiveness, springiness, adhesiveness and chewiness, was investigated. Samples containing higher coating concentrations (1–1.5%) showed higher rehydration capacity and lower browning index compared to those with lower coating concentrations (0.25–0.5%). Weibull distribution model was used to investigate the effect of coating concentration on drying kinetics. The results of sensory tests showed that the overall acceptance of samples is increased with decreasing coating concentration, and an appropriate correlation was found between sensory properties and textural parameters.