I Abbreviations and definitions Symbols of water status are standardized as follows: '1' ... total water potential; '1'" osmotic or solute potential; 'I' P' turgor or pressure potential. Throughout this text the term adaptation refers to heritable modifications in structures or functions that increase the probability of an organism surviving and reproducing in a particular environment (121); adaptations can be constitutive (always expressed) or stress-induced. When discussing stress metabolism, we have followed Hochachka (92) in making use of the term "design principle" in an engineering sense. In this sense, the design principles for a system are set by what that system is supposed to do under various circumstances; the design principles then determine what components must be included in the system, and how they must interact. An illustrative example: in automobile engineering. distinct design principles are involved for the two safety objectives of collision avoidance and injury mitigation (125a). Collision-avoid­ ance design principles are set by the aim of preventing accidents, and lead to the inclusion of system components such as dual-braking systems. Injury-mitigation design principles follow from the goal of protecting occupants in case of an accident; their application results in introduction of components such as energy-absorbing steering columns.

Metabolic Responses of Mesophytes to Plant Water Deficits

Water stress effects on rapeseed quality

Seeds of four lentil genotypes (Castelluccio, Eston, Pantelleria, and Ustica) were subjected to five levels (0, 10, 15, 18, and 21%) of polyethylene glycol (PEG-6000). Germination percentage, root length, tissue water content (WC), α- and β-amylases, α-glucosidase activities, and osmolyte content were evaluated at 24, 48, and 72 h after starting the germination test. Water stress reduced seed germination percentage, root length, and seedling WC in all cultivars to different extent. The increase in proline content and total soluble sugars was greater for Eston and Castelluccio compared to the other genotypes. The activity of the enzymes involved in the germination process decreased in all cultivars; the activities of α-amylase and α-glucosidase were most negatively affected by osmotic stress, mainly in the drought sensitive Ustica and Pantelleria. Overall, Eston and Castelluccio were able to express greater drought tolerance and consequently could be used as a valuable resource for breeding programs.

https://www.tandfonline.com/doi/pdf/10.1080/17429145.2013.835880

Effect of PEG-induced drought stress on seed germination of four lentil genotypes

RESEARCH ARTICLE Effect of PEG-induced drought stress on seed germination of four lentil genotypes

Effects of soil drought on growth and productivity of 16 single cross maize hybrids were investigated under field and greenhouse experiments. The Drought Susceptibility Index (DSI) was evaluated in a three year field experiment by the determination of grain loss in conditions of two soil moisture levels (drought and irrigated) and in a pot experiment by the effects of periodical soil drought on seedling dry matter. In the greenhouse experiment response to drought in maize genotypes was also evaluated by root to shoot dry mater ratio, transpiration productivity index, indexes of kernel germination and index of leaf injury by drought and heat temperature. The obtained values of DSI enabled the ranking of the tested genotypes with respect to their drought tolerance. The values of DSI obtained in the field experiment allow to divide the examined genotypes into three, and in the greenhouse experiment into two groups of drought susceptibility. The correlation coefficients between the DSI of maize hybrids in the field and the greenhouse experiments was high and statistically significant, being equal to 0.876. The ranking of hybrids drought tolerance, identified on the basis of field experiments was generally in agreement with the ranking established on the basis of the greenhouse experiment. In the greenhouse experiment statistically significant coefficients of correlation with DSI values in hybrids were obtained for the ratio of dry matter of overground parts to dry matter of roots, both for control and drought treatments, whereas in the estimation of the transpiration productivity coefficient and total dry matter the correlation coefficients were not statistically significant. In this study several laboratory tests were carried out for the drought tolerance of plants (kernel germination, leaf injury) on 4 drought resistant and 4 drought sensitive maize hybrids. Statistically significant correlation coefficients between DSI and the examined parameter of grain germination and leaf injury were obtained for the determination of promptness index (PI), seedling survival index (SS) and leaf injuries indexes (IDS, ITS) as a result of exposure to 14 days of soil drought, osmotic drought −0.9 MPa and exposure to high temperature 45 ° or 50 °C. The results of laboratory tests show that in maize the genetic variation in the degree of drought tolerance is better manifested under severe conditions of water deficit in the soil.

Genotypic variation between maize (Zea mays L.) single cross hybrids in response to drought stress

Genotypic variation in physiological and physicochemical parameters associated with drought resistance was observed between cultivars in Brassica napus and B. campestris. Significant variation in proline accumulation, chlorophyll stability, germination rate and percentage, relative turgidity, growth rates and water use efficiency were found in plants grown under simulated drought conditions in a glasshouse. No variation was detected between cultivars for leaf diffusive resistance or heat tolerance. A yield index for each cultivar was derived from yield performances in nine different field environments. Chlorophyll stability and proline accumulation in leaf tissue and germination percentage in solution equivalent to - 17.5 bars osmotic potential was clearly related to this yield index in B. napus and to a lesser extent in B. campestris. The winter cultivars of B, napus also possessed drought resistance characteristics, and they may be a valuable resource for the development of cultivars for droughted environments. Parameters were measured in a glasshouse, prior to anthesis, and therefore offer potential as ancillary selection criteria for drought resistance in oilseed rape growing in Western Australia.

Variation between and within Species of Rapeseed (Brassica campestris and B. napus) in Response to Drought Stress. III* Physiological and Physicochemical Characters

RA Richards

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Variation between and within Species of Rapeseed (Brassica campestris and B. napus) in Response to Drought Stress. III* Physiological and Physicochemical Characters