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Fresh, dried and rehydrated leaf samples of the resurrection plant, Sporobolus stapfianus , were analysed for their contents of low- M r substances. Glucose, fructose and sucrose were the prevailing sugars in aqueous extracts from fresh leaves, whereas sucrose accumulated in dried leaves. After 72 hr rehydration, an unusual content of mannitol and trehalose was observed. The involvement of fungal species, able to perform sugar biotransformations in rehydrated leaves, is reported.

Cereal plants become more resistant to freezing when first exposed to a period of cold-acclimation. Many physiological and molecular changes have been shown to occur at low temperatures, but the role and the contribution of each to frost resistance is still poorly understood. Two cultivars of barley (Hordeum vulgare L.), the winter barley Onice and the spring barley Gitane, were acclimated under controlled conditions under an 8-h photoperiod at 4°C (light) and 2°C (dark) for 21 days. Changes in free proline, ABA, water-soluble carbohydrates and free fatty acids were measured to assess their involvement in cold-acclimation and to explain the different frost-resistant capacities of the two cultivars. Exposure of barley plants to low temperature resulted in an equal increase in proline in both cultivars. During the first days of cold acclimation, ABA levels showed a peak in the frost-resistant cultivar, lasting about 24 h, followed by a decrease. The water soluble carbohydrates reached their highest content after 3 days of hardening, although after 14 to 21 days of acclimation the carbohydrate content was similar to that of unhardened plants. The frost-resistant Onice had a much higher free fatty acid content than the frost-sensitive Gitane. Furthermore in Onice 86% of free farty acids was represented by unsaturated molecular species. Inolenic acid alone being 71%. In contrast, in the frost-sensitive cultivar only 31% of free fatty acids was unsaturated and a large amount of 9-oxo-nonanoic acid, a product present in the linolenic acid cascade, was also detected. The ABA content after 2 days of hardening and the free fatty acid composition were clearly different between the two cultivars and may explain, at least in part, the different frost-resistant capacities of Onice and Gitane.

β-D-glucopyranosides, linked to C-2 or C-3 of the glycerol aglicone moiety, were unambiguously synthesized.

Sporobolus stapfianus Gandoger is a typical desiccation-tolerant or resurrection plant, which survives almost total dehydration. Samples of fresh

β-D-glucopyranosides, linked to C-2 or C-3 of the glycerol aglicone moiety, were unambiguously synthesized.

The main components of the chloroform-soluble epicuticular waxes from olive tree leaves (Olea europaea cvs Coratina and Cipressino), were triterpene oleanolic and betulinic acids and triterpenols sitosterol, α- and β-amyrin, uvaol and erythrodiol. The waxes of both cultivars contain the ubiquitous wax classes of alkanes, alcohols, aldehydes, fatty acids and alkyl esters. Methyl phenyl esters and 2-phenyl-ethanol-1-esters were both present in low amounts in cv. Coratina whilst cv. Cipressino contained only the former class of compounds. Furthermore cv. Coratina contained triacylglycerols that were missing in cv. Cipressino wax.

The chloroform-soluble waxes of green and black olive fruits ( Olea europaea cv Coratina) contain alkanes (C 23 –C 33 ), saturated and unsaturated alkyl esters (C 38 –C 56 ), aldehydes (C 24 –C 30 ), methyl phenyl esters, triacylglycerols, alcohols (C 22 –C 28 ), fatty acids (C 16 –C 28 ), and pentacyclic triterpenols and triterpenoid acids. Oleanolic acid and triacylglycerols are the major components. Uvaol and erythrodiol, present in substantial amount in wax from green olives, were present only in trace amounts in that from black olives.

Craterostigma plantagineum, a resurrection plant, displays extreme desiccation tolerance; dehydrated leaves and ABA-treated calli resume a normal metabolic state upon rehydration. Samples of calli and leaves of C. plantagineum were analysed for the major classes of compounds such as sugars, fatty acids, amino acids and derivatives, and phytosterols. Calli solutes are characterized by large amounts of glutamine and tyramine, triterpene acids and colneleic acid, an inhibitor of lipoxygenase. Among the sugars extracted from calli, sucrose, together with its hydrolytic products, predominates, while maslinic, ursolic and oleanolic acids are the most important triterpenes. In leaves the most common triterpene alcohols were campesterol, stigmasterol and β-sitosterol. Almost 50% of the weight of the lyophilized material consisted of 2-octulose, a sugar present as a minor component in a limited spectrum of plant species. Acquisition of desiccation tolerance in ABA-treated and desiccated calli was accompanied by an increase of fatty acids, accumulation of colneleic acid and by the disappearance of glucose and fructose. The most relevant biochemical effect of desiccation on leaves was the conversion of 2-octulose into sucrose.

Boea hygroscopica is a poikilohydrous plant. This and similar species are also called desiccation-tolerant or resurrection plants. They have the unique ability to revive from an extreme air-dry condition. Samples of fresh, dried and rehydrated leaves were analysed for the major classes of organic substances like sugars, alditols, inositols, fatty acids, amino acids, betaines, phytosterols and others. The compounds which accumulated in desiccated leaves were sucrose and polyunsaturated C 18 acids. Abietanes and pimaranes were also detected. Monosaccharides, which are present in fresh leaves, disappeared, whilst phytosterols, stearic and oleic acids decreased to low levels; paimitic acid was unchanged. Rehydration of dried leaves seemed to restore the chemical composition of unstressed leaves. Betaines were not detected in any of the plant samples examined.

Wax components of the aerial parts of mature plants of Sorghum bicolor were compared with those from the panicles and mature grains. Lipid content of the grain flour was also analysed. Attention has been paid to the polycyclic triterpenes distributions comparing different varieties of sorghum. The general occurrence of hopanoids suggests that they are significant chemotaxonomic markers for S. bicolor. Dotriacantanol was found to characterize the lipid content of the grain flour. Observations on this finding are reported.

The chloroform extractives of four wild selections of Zea mays pollen were separated quantitatively into chemical classes and the components of each class were identified. Alkanes, alkenes, fatty acids, triterpene esters and triglycerides were found as the main constituents of the lipid extracts. The two hydrocarbon classes were found in a ratio close to 1:1; pentacosane, heptacosane and nonacosane were dominating in the alkanes, whilst alkenes showed major homologues two carbon atoms longer. Free fatty acids, 8–22% of the total, contained predominantly palmitic (16:0), stearic (18:0), oleic (18:1), linoleic (18:2) and lower amounts of palmitoleic (16:1) and linolenic (18:3) acids. Triglycerides and triterpene esters accounted for 17–31 % and 5–34%, respectively. The former class comprised three homologous series, the latter contained tetracyclic and pentacyclic triterpenes esterified with C16 and C18 fatty acids. Free triterpenols and linear esters were also found in pollen lipids. These data are discussed in relation to pollen biochemistry and in regard to the natural functions of the lipid classes found.

The influence of growing season on some physiological and biochemical variates related to fruit yield and quality was investigated in melon (Cucumis melo L.) plants cultivated in nutrient film tech...

Our previous experiments on desiccation tolerance in immature embryos of maize cast doubt on a crucial role of high concentrations of sucrose and high raffinose to sucrose mass ratio. In the present work we report experiments aimed at gaining a further insight into the above mentioned subject and to ascertain whether endogenous ABA may stimulate the accumulation of sucrose. Immature and desiccation sensitive embryos of maize were isolated and exposed to different drying conditions either leading or not leading to desiccation tolerance acquisition and allowing for different ABA and sugar responses. ABA concentrations as well as sugar concentrations were compared in embryos undergoing such different dehydration treatments. We conclude that in maize embryos: 1) sucrose, even at high concentrations, is not the sole factor responsible for desiccation tolerance; 2) high sucrose concentrations do not appear to be an absolute requirement of desiccation tolerance; 3) a high (>0.05) raffinose to sucrose mass ratio is not a prerequisite of desiccation tolerance; 4) ABA doesn’t seem to stimulate sucrose accumulation. We suggest that desiccation tolerance can occur even in the absence of raffinose.

Many physiological and molecular changes have been shown to occur at low temperatures, but the role and the contribution of each to frost resistance are still poorly understood. These changes include variations in enzyme activity, accumulation of soluble components, alterations in membrane composition and induction of specific genes.

The structural composition is reported of epicuticular wax esters from maize. The waxes from wild type ( Gl ) plants at different stages of growth and those from some glossy ( gl ) seedlings and an albino strain of maize have been analysed for their content of esters. Influence of age and mutations on the epicuticular wax ester composition is discussed.