LarssoD, S. and Svenningsson, M. 1986. Cuticular tran^iratioo and epicuticular lipids of primary leaves of barley (Hordeum vulgare) . Twenty cultivars of barley and 15 eceriferum mutants from one of the cultivars have been analysed for cuticular transpiratioii and epicuticular lipids of their primary leaves. The relative cuticular transpiration rates of the cultivars ranged from 0.61 to 1.98. In spite of this variation in transpiration most of the cultivars had almost the same amount of epicuticular lipids per leaf area, about 16 |i.g cm'^. The eceriferum mutaats showed a wider range in amount of epicuticular lipids, from 5.0 to 15.5 ng cm"^. Nevertheless, most of the mutants transpired almost at the same rate. Only a weak correlation was found between cuticular transpiration and total amount of epicuticular lipids. None of the analysed lipid components (aikanes, aldehydes, primary alcohols, esters or fatty acids) was better correlated to the cuticular transpiration than the total amount of lipids. When the cultivars were exposed lo a mild water stress their cuticular transpiration rates decreased by about 31%. This reduction was not accompanied by any corresponding increase in total amount of epicuticular lipids. Tlie most pronounced effect of the water stress treatment was a stimulation in the ester formation and a reduced formation of primary alcohols. This shift in lipid composition could not be correlated to the decreased cuticular transpiration rates of the individual cultivars. From this investigation it is concluded that the cuticular transpiration is poorly correlated to the amount or composition of the epicuticular lipids in this barley material. As a cotisequence it was not possible to use any characteristic of the epicuticular hpids as a selection criterion in breeditig for drought resistance.Additional key word -Drought resistance. 5. Larsson (reprint requests), Svalof AB, S-268 00 Svalov, Sweden and Af. Svenningsson,

Two cultivars of oat (Avena sativa L. cvs Pendek and Stormogul II) were exposed to short periods of water‐deficit stress on five consecutive days. The plants responded to the stress by decreasing their cuticular transpiration rate. After two stress periods the cuticular transpiration rate was reduced by 30% for Pendek and by 47% for Stormogul II, and after another three stress periods by 30% and 20%, respectively. These reductions were correlated neither to changes in the total amount of what is generally called epicuticular lipids, nor to changes in any of the major individual constituents of the epicuticular lipids (alkanes, free and esterified fatty acids or free primary alcohols). After removal of the epicuticular lipids the long chain free primary alcohols of the leaves were extracted and determined. The amount of these presumably intracuticular alcohols increased after stress and changed to shorter chain length. From these results it is concluded that the intra‐ as well as the epicuticular lipids must be taken into consideration when discussing leaf surface lipids as protecting agents against water loss.

High performance liquid chromatography (HPLC) analytical studies of inner bark extractives from a large number of silver birch (Betulapendula Roth) and hairy birch (Betulapubescens Ehrh.) trees revealed the diarylheptanoid glucoside platyphylloside to be present at high levels in B. pendula (20–60 mg/g dry bark) and at low levels in B. pubescens (≤ 0.5 mg/g dry bark). Based on these observations, a new simple and accurate precipitation method to distinguish between B. pendula and B. pubescens has been developed. In a solution of 2,4-dinitrophenylhydrazine, platyphylloside immediately forms an orange precipitate. A similar precipitate is also produced when a piece of B. pendula inner bark is kept for 1 h at room temperature in the same solution. However, no precipitate forms when a sample from B. pubescens is used. The diagnostic value of morphological characters was assessed by comparing the results of species determinations made on a large number of trees (> 1600), both juvenile and mature, using the morphological and the new chemical method. For birches younger than 20 years there was 100% agreement between the two methods. However, in some mature birch stands with the two species mixed and ages over 40 years, up to 20–30% of the trees were incorrectly identified to species using morphological characters. Results from tests using the precipitation method on birch species, varieties, forms, and hybrids were reported.

No abstract

The major constituents of the epi‐ and intracuticular lipids of primary leaves of 8 cultivars of barley (Hordeum vulgare L.) have been studied together with cuticular transpiration rates. The total amount of analysed cuticular lipids ranged from 9.6 to 13.4 μg cm−2 and was dominated by the epicuticular fraction, which made up 73–84% of the total. There were variations in the percentages of the analysed lipid classes, alkanes, esters, aldehydes, β‐diketones and alcohols, between epi‐ and intracuticular lipids among individual cultivars, but no clear tendency in these variations, except for the aldehydes, was found. The epicuticular lipids were richer in aldehydes than the intracuticular lipids. The cuticular transpiration rates were poorly correlated with the levels or composition of epi‐, intra‐ or total cuticular lipids. The cuticular transpiration rates were considerably altered as a response to a water stress treatment, but these changes could not be correlated with any changes in amount or composition of the cuticular lipids. From these results it is concluded that some property other than amount or composition of cuticular lipids is the most important in regulation of water diffusion through the cuticle.