Young barley seedlings (Hordeum vulgare L.) were stressed using nutrient solutions containing NaCl or polyethyleneglycol (PEG) and measurements were made of leaf growth, water status, proline soluble sugar contents of growing (basal) and non-growing (blade) tissues. Leaf growth ceased within seconds following exposure of seedlings to osmotic solutions with water potential values (ψ) = -3 to -11 bars but growth resumed after a lag period. Latent periods were increased and new growth rates were decreased as ψ of nutrient solutions were lowered. Growth ceased before detectable changes occurred in tissue water status but leaf basal tissues began to adjust osmotically, and reductions of 1 to 2 bars in both ψ and osmotic potential (π) usually occurred for the first 1 to 2 hours with lower reduction rates thereafter. After 1 to 3 days exposure of seedlings to solutions with different ψ, cumulative leaf elongation was reduced as the ψ of the root medium was lowered. Reductions in ψ and π of tissues in leaf basal regions paralleled growth reductions, but turgor (P) was largely unaffected by stress. In contrast, ψ, π and P of leaf blades were usually changed little regardless of the degree and duration of stress, and blade ψ were always higher than ψ of basally located cells. It is hypothesized that blades have high ψ and are generally unresponsive to stress because water in most of the mesophyll cells in this area does not exchange readily with water present in the transpiration stream. Measurements of proline contents in different sections of leaf following water stress, showed that in living tissues proline levels are dynamically related to water status of the tissue. In the basal regions where reductions in ψ and π occurred rapidly, proline levels were elevated quickly, whereas, accumulation of proline in mid-blade tissues occurred slowly and in lower concentrations. The combined data of many experiments showed a strong correlation between proline levels and tissue ψ (r = 0.93) and π (r = 0.85). Increase in total soluble sugars (TSS) and ion concentrations, contributed significantly to the stress-induced osmotic adjustment observed in the growing tissue.

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Call number: LD2668 .T4 1952 A4 / Master of Science

Making quality and winterhardiness in barley are "ultimate" phenotypes composed of component, quantitatively inherited traits. A 69-point genome map of the seven chromosomes of barley was used, in conjunction with multi-environment phenotypes for grain yield and malting quality, to determine the chromosome locations of quantitative trait loci (QTLs). A combined analysis of the two environments identified QTLs that were both common and unique to each environment. Dispersed QTLs with positive relationships provide ready targets for marker-assisted selection. Overlapping QTLs for agronomic and making quality QTLs with favorable alleles contributed by alternate parents will require further, higher resolution mapping to determine if negative relationships are due to linkage or pleiotropy. There is preliminary evidence for orthologous agronomic trait and malting QTLs in barley. This QTL analysis will hopefully assist in the rapid development of winter making varieties that will maximize the profitability of Oregon barley production. / Graduation date: 1994

Graduation date: 1991