The Role of Transpiration in Phototropism of the Avena Coleoptile: Evidence of Stomatal Control of the Phototropic Response

1994 ◽  
Vol 21 (3) ◽  
pp. 359 ◽  
Author(s):  
GI Mcintyre
Keyword(s):  
Positive Curvature ◽  
Tritiated Water ◽  
Petroleum Jelly ◽  
Phototropic Response ◽  
Avena Coleoptile ◽  
Nail Polish ◽  
Basal Half ◽  
Apical Half ◽  
Effect Of Light

The hypothesis that phototropism is caused by the effect of light on transpiration seemed at variance with the observation that Avena coleoptiles respond phototropically while submerged in water. Further investigations, however, provided evidence that phototropism of submerged coleoptiles may be caused by the light-induced promotion of stomatal guttation. Evidence of guttation by submerged coleoptiles was provided by measuring tritium accumulation in a water jacket surrounding the coleoptile when tritiated water (THO) was supplied to the roots. It was shown that the application of nail polish to the coleoptiles induced almost immediate guttation from the stomata. This response, measured quantitatively by image analysis, occurred predominantly on the irradiated side of coleoptiles previously stimulated phototropically with blue light while submerged in water, and was much reduced and more uniformly distributed when the phototropic response had been eliminated by saturating the water with CO2. Small curvatures exhibited by coleoptiles kept in the dark at high humidity were almost invariably towards the side from which guttation occurred from the apical (hydathode) stomata. Application of petroleum jelly (Vaseline) to the stomata on the illuminated side of coleoptiles stimulated phototropically in moist air induced a negative curvature in the apical half of the coleoptile and reduced the positive curvature in the basal half. In contrast, vaseline applied to the middle of one of the broad sides of the coleoptile, where no stomata occur, had relatively little effect. These results are consistent with the hypothesis that phototropism of the Avena coleoptile is caused by light-induced loss of water from the stomata. It is also postulated that the mechanism is essentially the same whether water is lost by transpiration or guttation.

New injurious Curculionidae (Col.)

1931 ◽  
Vol 22 (3) ◽  
pp. 417-421 ◽  
Author(s):  
Guy A. K. Marshall
Keyword(s):  
Median Carina ◽  
Basal Half ◽  
Transverse Stria ◽  
Apical Half ◽  
Basal Width

Aedophronus echinatus, sp. n. (Pl. xxi, fig. 2).Derm black, with dense brown scaling, usually with an indefinite mottling of darker and paler scales ; the inflexed margins of the elytra fuscous.Head not very convex, with the median stria extending to the vertex and the anterior transverse stria slightly curved ; the infra-ocular margin much narrower than the base of the scape and not projecting ; the setae short, stout and curved backwards ; the eyes comparatively large, highest much behind the middle, and with the hind margin devoid of scaling. Rostrum longer than the head (5·5 : 4), much shorter than its basal width (5·5 : 7·5), narrowed in front, straight at the sides, with a shallow impression on the apical half and with no median carina ; the marginal carina of the epistome obtuse but distinct. Prothorax transverse (3·5 : 6), strongly rounded at the sides, widest at the middle, subtruncate at the apex, which is only slightly narrower than the base ; the dorsum with an abbreviated median stria on the basal half and bearing on the disk short curved setae like those on the head, the lateral ones much longer, stout, straight and pointed (when unbroken), the longest being about as long as the scape.

Inhibition by carbon dioxide of the phototropic response of the Avena coleoptile to blue light

1987 ◽  
Vol 65 (3) ◽  
pp. 488-490 ◽  
Author(s):  
Gordon I. McIntyre
Keyword(s):  
Carbon Dioxide ◽  
Blue Light ◽  
Avena Sativa ◽  
Water Saturation ◽  
Phototropic Response ◽  
Avena Coleoptile ◽  
Inhibition Of Growth ◽  
Saturated Water ◽  
Coleoptile Elongation

When intact oat coleoptiles (Avena sativa var. Harmon) were submerged in water, saturation of the water with CO2 promoted their elongation but eliminated their phototropic response to blue light. Increasing the pH of the CO2-saturated water prevented the promotion of coleoptile elongation but did not prevent the elimination of the phototropic response. In air, phototropic curvature was significantly reduced by 10% CO2 and was eliminated by 30%, without any reduction in growth. It is postulated that the increase in CO2 concentration may eliminate the phototropic curvature of the coleoptile by preventing the light-induced inhibition of growth on the illuminated side of the organ. Possible mechanisms are briefly discussed.

scholarly journals A Phenomenological Analysis of Freckling in Directional Solidification of Ni-Base Superalloy: The Role of Edge and Curvature in Casting Components

2019 ◽  
Vol 51 (1) ◽  
pp. 88-92 ◽  
Author(s):  
D. X. Ma ◽  
Z. H. Dong ◽  
F. Wang ◽  
H. B. Dong
Keyword(s):  
Directional Solidification ◽  
Positive Curvature ◽  
Phenomenological Analysis ◽  
Geometrical Factor ◽  
Freckle Formation ◽  
Base Superalloy

Abstract The geometrical factor in freckle formation has rarely been taken into account. In this work, freckle formation in superalloy components is examined. It is found that freckle formation is subject to the effects of the edge and curvature. In polygonal casting sections, freckles are formed preferably on the convex edges. In the components with a curved contour, freckles are exclusively formed on the outward-curving surface having positive curvature.

The role of fractures and lipids in the seed coat in the loss of hardseededness of six Mediterranean legume species

2005 ◽  
Vol 143 (1) ◽  
pp. 43-55 ◽  
Author(s):  
L. W. ZENG ◽  
P. S. COCKS ◽  
S. G. KAILIS ◽  
J. KUO
Keyword(s):  
Seed Coat ◽  
Lipid Content ◽  
Environmental Scanning Electron Microscopy ◽  
Environmental Scanning ◽  
Petroleum Jelly ◽  
Physicochemical Changes ◽  
Ornithopus Sativus ◽  
Seed Coats ◽  
Seed Coat Morphology

Changes in the seed coat morphology of 12 annual legumes were studied using environmental scanning electron microscopy (ESEM). The seeds of Biserrula pelecinus L. cv. Casbah, Ornithopus sativus cv. Cadiz, Trifolium clypeatum L., T. spumosum L., T. subterraneum L. cv. Bacchus Marsh, Trigonella balansae Boiss. & Reuter., Trigonella monspeliaca L. and Vicia sativa subsp. amphicarpa Dorthes (morthes.) were examined by ESEM after exposure to field conditions for 6 months, while those of Medicago polymorpha L. cv. Circle Valley, Trifolium clypeatum L., T. glanduliferum Boiss., T. lappaceum L., T. spumosum L., and T. subterraneum L. cv. Dalkeith, were examined after 2 years' exposure. The entry of water into seeds was followed by covering various parts of the seed coat with petroleum jelly and soaking the treated seeds in dyes.As the seeds softened over time, more and larger fractures appeared on the seed coat. Water entered the seed either through fractures, over the seed coat as a whole or through the lens. It is hypothesized that the formation of fractures occurs after physicochemical changes in the seed coat, probably associated with changes in the amount and nature of seed coat lipids.The newly matured whole seeds of M. polymorpha cv. Circle Valley, T. clypeatum, T. glanduliferum, T. lappaceum, T. spumosum, and T. subterraneum cv. Dalkeith were analysed for lipid content in 1997. The seed coats of T. subterraneum cv. Dalkeith and T. spumosum were separated from the cotyledons and examined in detail for lipid content.The lipid content of whole seeds ranged from 48 (T. lappaceum) to 167 mg/g (T. subterraneum cv. Dalkeith). Total lipid of the whole seeds of T. subterraneum cv. Dalkeith and T. glanduliferum declined by about 9 mg/g over 2 years, while in T. spumosum it declined by about 17 mg/g.In contrast, the major fatty acids in the seed coat declined by 0·67 mg/g over the 2 years. Change in seed coat lipids showed a marked similarity to changes in hardseededness for both T. subterraneum cv. Dalkeith and T. spumosum. The results strongly suggest that seed softening is associated with loss of lipids in the seed coat, because lipids have physical characteristics that are altered at temperatures experienced in the field.

Effect of light on birnessite catalysis of the Maillard reaction and its implication in humification

2001 ◽  
Vol 81 (3) ◽  
pp. 277-283 ◽  
Author(s):  
A. Jokic ◽  
A I Frenkel ◽  
P M Huang
Keyword(s):  
Humic Substances ◽  
Maillard Reaction ◽  
Solid Phase ◽  
Natural Environments ◽  
Promoting Effect ◽  
Nitrogenous Compounds ◽  
Heterogeneous Catalytic ◽  
Catalytic Role ◽  
Effect Of Light

The Maillard reaction between carbohydrates and nitrogenous compounds originally investigated in 1912 has subsequently been proposed as a possible pathway for the formation of humic substances in natural environments. However, the role of mineral catalysis of the Maillard reaction is little understood and the promoting effect of light on such catalysis is not known. Birnessite (δ-MnO2), which is commonly present in soil environments, was investigated for its activity in promoting the Maillard reaction between glucose and glycine at a light intensity of 168 µE s–1 m–2 or in the dark. The presence of substantial quantities of Mn(II) was detected in both the supernatant and solid phase of the glucose-glycine-birnessite systems. The spectroscopic evidence indicates that birnessite, in the presence of light, is a very effective catalyst in abiotic browning of solutions of glucose and glycine. Furthermore, birnessite significantly promoted the reaction even in the absence of light. Therefore, the abiotic heterogeneous catalytic role of soil minerals such as birnessite in polycondensation of simple sugars and amino acids merits close attention in the formation of humic substances in natural environments. Key words: Maillard reaction, heterogeneous catalysis, light, birnessite, humic substance formation, XANES

scholarly journals Effect of CO2 treatment on dormancy duration, sprout growth and sugar content in two potato cultivars: Short communication

2011 ◽  
Vol 32 (No. 2) ◽  
pp. 68-73
Author(s):  
R. Ezekiel ◽  
B. Singh
Keyword(s):  
Short Communication ◽  
Sugar Content ◽  
Fold Increase ◽  
Potato Cultivars ◽  
Total Sugars ◽  
Apical Buds ◽  
Basal Half ◽  
Apical Half ◽  
Subsequent Storage ◽  
Sprout Growth

Dormant tubers of two potato cultivars Kufri Jyoti and Kufri Chandramukhi were treated for 7 days with 5, 10, 15 and 20% CO<sub>2</sub> concentrations at 18 &plusmn; 1&ordm;C and 90&ndash;95% RH, and compared with GA treated tubers and with untreated tubers serving as control. During subsequent storage at the same temperature and RH, dormancy duration was reduced by 20 days with CO<sub>2</sub> treatment and by 35 days with GA treatment. In Kufri Jyoti, GA treatment caused 2.6 fold increase in the concentration of reducing sugars and 0.8 fold increase in total sugars in the apical half of the tubers leading to early release of dormancy in apical buds but this increase in sugar content was not observed in the basal half where the buds remained dormant. &nbsp;

Braconidae : Notes and new Species

1931 ◽  
Vol 22 (1) ◽  
pp. 75-82 ◽  
Author(s):  
D. S. Wilkinson
Keyword(s):  
New Species ◽  
Posterior Margin ◽  
The Other ◽  
Lateral Carina ◽  
Median Carina ◽  
Other Hand ◽  
Basal Half ◽  
Apical Half

Rhaconotus mahensis, sp. n.♀♂. Black ; scape and all legs red testaceous ; ovipositor bright red ; flagellum red-brown, possibly rather darker at apex ; wings hyaline, the setae with a distinctly fulvous tinge, and the stigma hyaline (at least not darkened).♀♂. The integument is not coriaceous throughout, and is only sparsely clothed with setae (except on the flagellum and possibly the legs). Head smooth and highly shining, not coriaceous, impunctate, the vertex and occiput almost entirely devoid of setae ; antennae longer than head, thorax, and abdomen together ; flagellar joints in ♀ 29–33, in ♂ 26–28. Thorax : mesonotum dully shining, coriaceous ; the notauli well marked, joining slightly before reaching the posterior margin of the mesonotum ; propodeon with five longitudinal carinae, one in the middle and two on each side, these latter rather more closely placed to each other than to the median carina ; this median carina is discernible as such only in the basal half of the propodeon, thereafter becoming lost amongst the reticulate wrinkles with which the apical half of the propodeon abounds ; the lateral carinae, on the other hand, are discernible more or less throughout their length, particularly the inner pair which can generally be traced to the median apex of the propodeon where they join each other ; the integument of the basal half of the propodeon coriaceous on each side of the median carina as far as the first lateral carina, thereafter wrinkled as in the apical half.

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