Epidermal conductance in different parts of durum wheat grown under Mediterranean conditions: the role of epicuticular waxes and stomata

Abstract. Epidermal (non-stomatally-controlled) conductance from the fourth leaf, first node leaf, flag leaf and ear of durum wheat (Triticum turgidum var durum L.) grown under Mediterranean field conditions has been measured, along with leaf stomatal frequency and the amount and distribution of epicuticular waxes. Measurements were carried out on varieties and land-races from the Middle East, North Africa, ‘Institut National de la Recherche Agricole’ (INRA) and ‘Centra Internacional de Mejora de Maiz y Trigo’ (CIMMYT). Significant differences were observed among genotypes in the epidermal conductances (g_e) of the four organs. For each of the four organs tested, genotypes from the Middle East and CIMMYT showed higher g_e. values than those from North Africa and INRA. Ears showed epidermal conductances that were more than four times higher than those of leaves when g_e. values were expressed per unit dry weight. The amount of epicuticular waxes was higher in the fourth leaves, intermediate in the first node and flag leaves and lower in the ears. For each organ, g_e differences among genotypes were unrelated with the amount of epicuticular waxes. Removal of epicuticular waxes by dipping the organs into chloroform significantly increased the epidermal conductance for the fourth and first node leaves and the ear. However, this did not occur for the flag leaf. For the fourth leaf, g_e of intact leaves and g_e of leaves in which epicuticular waxes were removed were unrelated (r = -0.265). The regression coefficient of this relation for the first node and flag leaves showed values of 0.666 and 0.650 (P > 0.05), respectively, and values were even higher in the ear (r > m 0.892, P > 0.01). Scanning electron microscope analysis showed that wax bloom decreased from the fourth leaf to the flag leaf, whereas the extent of amorphous wax increased. Wax bloom in leaves consisted mainly of deposits of thin wax plates. In the ears and the adaxial surface of flag leaves, fibrillar waxes predominated. In the first node and flag leaves, the wax deposits on the adaxial side cover the surface of the leaf more densely and uniformly than those on the abaxial side. There was no significant correlation between g_e and total stomatal density, or between g_e and either adaxial or abaxial stomatal density for any sample of the three different leaves. The contribution of epicuticular waxes plus total stomatal frequency only explained 42.4, 11.8, 28.3 and 16% of g_e (per unit leaf area) variations for the fourth leaf, first node leaf, flag leaf and the combined variation of the three leaves together, respectively. From these results, it is concluded that complex interrelationship between different morphophysiological characteristics probably control g_e differences among genotypes and that these interrelationships differ for each different plant part.     

Freeze-preservation of buds from Scots pine trees

A procedure has been developed for freeze-preservation of buds of the Scots pine (Pinus sylvestris L.). Instead of liquid nitrogen, cold storage in –80°C was used. The partly dormant material used in the experiments was obtained directly from a natural stand in Northern Finland and no prefreezing or cryoprotectants for preconditioning were used. Cooling velocity was 1°C/min up to a terminal freezing temperature of –39°C, after which the buds were immersed in liquid nitrogen at –196°C for 10 minutes. The material was then transferred to a deepfreezer at –80°C and stored up to 6 months. After rapid thawing, the buds were sterilized and their viability was tested by FDA staining and by culturing meristems on 1/2 MS medium for at least two weeks. All the freezing experiments were performed during March and April. The best survival of buds (90–100%) was achieved at the beginning of April, after which a pronounced decline in survival occurred obviously due to a rise in the water content of the buds.     

Compensatory growth in shoot populations of young white pine trees

Summary White pine (Pinus strobus L.) trees have shoot populations composed of subpopulations of terminal and lateral shoots. I tested whether the subpopulations would show compensatory (increased) growth when separated from each other. Ten-year-old white pine (Pinus strobus L.) trees growing under an oak (Quercus) overstory were untreated or treated in winter by removing either all terminal, or all lateral buds (10 trees per treatment). Growth was compared between control and treated shoot subpopulations. In the 1st year, shoot-length frequency distributions were similar between control and treated subpopulations. There was significant compensatory shoot elongation (mean of 1.5 cm per shoot) in both treated subpopulations. In the 2nd year each subpopulation produced both terminal and lateral shoots. Shoot-length frequency distributions were similar, but shifted toward longer shoots in treated populations. Shoot number, mean length and total shoot length were greater in treated populations. The increased growth in treated subpopulations was due both to differences in parent shoot length and to compensatory shoot production and elongation.     

栽培中华猕猴桃的染色体观察

对原产地位于赣鄂边界幕阜山地区的十二个大果型中华猕猴桃优株或株系的染色体数目观察表明,这些栽培类型全部为四倍体,2n=4x=116。讨论了染色体倍性与果实大小的关系及几种可能的育种方法。     

广西大戟科植物资料

<正> 广西的大戟科植物种类众多。作者对广西中草药原植物研究过程,将已采集的标本及华南植物所标本室(SCBI)和广东、广西主要标本室(均有注明)收藏的广西及其邻近地区的大戟科标本进行整理;现报道(一)、三宝木属植物摘记;有5种和3个新变种,其中广西产5种、1变种。(二)、广西白大凤属植物;1种。     

人工樟子松—差不嗄蒿植被及其固沙作用

植物固沙是整治沙漠和沙漠化土地的一种有效措施。人工植被的建立是植物固沙的必然结果。人工植被的演替、稳定性及其对环境的影响直接关系到流沙的固定程度。因此,本文旨在探讨人工樟子松(Pinus sylvestris var.     

云南松林的生物量研究

本文研究了云南省易门县海拔1600—1700m的云南松中幼龄林分的生物量。云南松林的生物量随林龄的增加而增加。4年生林分的总生物量为9.985吨/公顷,11年生林分为27.874吨/公顷,23年生林分为69.852吨/公顷。乔木层的器官生物量分配比例随林龄而变化。针叶和树皮的分配比例随林龄的增加而迅速下降;干材和根的比例则不断上升,其中以干材增加最快;树枝的分配比例以11年生林分最大,23年生林分次之,4年生林分最小。     

Pathogenicity of Bursaphelenchus xylophilus on Pines in Minnesota and Wisconsin

The pinewood nematode, Bursaphelenchus xylophilus, was inoculated into established native jack and red pines (Pinus banksiana and P. resinosa) and exotic Austrian pine (P. nigra) in Minnesota and Wisconsin forests during summer 1981. The nematode isolates did not kill established nonstressed pine trees growing in the forest. However, the same nematode isolates killed pine seedlings under greenhouse conditions. Girdling the main stem of some trees to induce stress resulted in the death of the majority of inoculated and noninoculated branches of Austrian and jack pines, but no branch death was observed on red pine. Greater numbers of nematodes were extracted from branches of inoculated, girdled trees than from nongirdled trees. The mean number of nematodes extracted from branches of inoculated, nongirdled trees was 0.3 - 14 nematodes per gram of wood.