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Open access

D.C. Milbocker

Abstract

Conventional leafburn evaluations were compared with a new root cell plasmolysis technique to test azalea cultivars (Rhododendron sp.) for salt tolerance. Plasmolysis was a more rapid indicator of salt tolerance than leafburn evaluation, and the technique was an acceptable method of evaluating azalea salt tolerance. Results of this research indicated that the salt-tolerant group contained those species and cultivars considered sun-tolerant, which are characterized by large leaves, coarse stems, and rapid growth. Kurume azaleas were among those determined to be salt-sensitive.

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Agnes A. Flores-Nimedez, Paul H. Li, and Charles C. Shin

GLK-8903, an experimental product whose main ingredient is produced by hydrogenation of a primary alcohol extracted from plants, showed significant potential in protecting bean (Phaseolus vulgaris L.) plants from chilling injury. The GLK-8903 protection mechanism was assessed by examining several physiological and biochemical responses. The decline in leaf water potential and the increase in osmotic potential caused by chilling exposure to 4C (day/night) were minimized by the application of GLK-8903. Chilling causes an increase in electrolyte leakage, an indication of chilling injury of the plasma membrane. Increased electrolyte leakage was reduced significantly in the GLK-8903-treated plants during chilling. This minimized leakage may be due to less damage of the plasma membrane. Plasmolysis and deplasmolysis studies of the epidermal cells suggest that GLK-8903 is able to reduce the plasma membrane perturbation in the chilling environment, as evident by: 1) the lower permeability coefficient to urea at 4C, and 2) the swelling of protoplasts in the cells of untreated tissues after chilling exposure with no swelling of the protoplast being observed in the GLK-8903-treated cells. Malondialdehyde (MDA), a product of lipid peroxidation, increased more in untreated controls than in treated plants exposed to 4C. Plasma membrane ATPase activity decreased less in GLK-8903-treated plants than in untreated controls after 3 days at 4C. The mechanism of GLK-8903-alleviated chilling injury is discussed.

Open access

F. J. Dainello

Abstract

Germinated spinach (Spinacia oleracea L.) seed (radicle length 3 to 12 mm) were subjected to dehydration under uncontrolled room conditions for 3 to 25 days before planting. Although diminishing over time, some seedlings emerged after all dehydration periods. Seedling height and dry weight responded similarly. Dehydration of germinated seed for ≥15 days was required before seedling emergence was reduced by 50% of that produced by undehydrated germinated seed. Three cultivars responded similarly to length of dehydration period in respect to seedling emergence and vigor.

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Eckhard Grimm and Moritz Knoche

used microscopy and a plasmolysis technique to limit our analyses just to the epidermal cell layer. The same values for the flesh were measured conventionally using osmometry. Materials and Methods Plant material. Fruit of the sweet cherry cultivars

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Albert H. Markhart III and Mark S. Harper

Leaves on cut stems of commercially grown Rosa hybrida cv. Kardinal placed in preservative solutions containing sucrose developed necrotic dry patches that began interveinally and progressed toward the major veins until the entire leaf was dehydrated. Ultrastructural observations of initial damage showed disorganized protoplasm and plasmolyzed cells. Leaves on cut stems pretreated with abscisic acid for 24 hours and transferred to preservative solution containing sucrose remained healthy. We propose that sucrose accumulates in the mesophyll cell wall, thus decreasing apoplastic osmotic potential, leading to cell collapse and tissue death.

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ZhaoSen Xie, Charles F. Forney, WenPing Xu, and ShiPing Wang

control fruit, showing plasmolysis in CC. ( C ) A mature SE/CC complex in a fruit produced under root restriction showing more serious plasmolysis in CC. ( D ) A mature SE/CC complex in a fruit produced under root restriction showing dense cytoplasm with

Open access

Nu-may R. Reed and Hudson T. Hartmann

Abstract

Following the application of 2-chloroethyl-tris-(2-methoxyethoxy)-silane (CGA 13586), an ethylenereleasing compound, to olive (Olea europaea L.) shoots, 2 abscission zones were observed. One occurred at the proximal, the other at the distal end of the pedicel. Actual separation occurred mostly at the distal end of the pedicel. Changes observed during the development of the abscission zone included: cell plasmolysis, cell wall and middle lamella dissolution, starch grain accumulation and a general breakdown of cells at the abscission zone.

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Marie-Therese Charles, Alain Goulet, Francois Castaigne, and Joseph Arul

Hormic dose of ultraviolet light (3.7 kJ•m-2) induced disease resistance in tomato fruit. The biochemical nature of induced resistance by UV light was investigated by histochemical techniques. Ultraviolet light induced plasmolysis of the epicarp and few mesocarp cell layers, and collapse of these cell layers led to the formation of cell wall stacking zone (CWSZ). The treatment also stimulated the biosynthesis of phenolic compounds (Prussian blue reaction) in the epicarp and mesocarp cells. Biochemical reinforcement of the cell wall through lignification (Maule test) and suberization (berberine fluorescence) was also induced. These responses originating from the activation of phenylpropanoid path were principally localized in the CWSZ and were induced before inoculation by B. cinerea. The intensity of these responses was significantly increased in UV-treated tissue in response to infection. These responses were also induced in the inoculated control tissue but were either less substantial (phenolics, lignification, and suberization) or delayed.

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B.R. Bondada, R Romero-Aranda, J. Syvertsen, and L. Albrigo

Foliar applications of urea-nitrogen are widely used to alleviate N deficiencies in citrus; however, improper applications can cause serious foliar burn and loss of active green leaf area. Light (LM), transmission (TEM), and scanning (SEM) electron microscopy were used to characterize anatomical and ultrastructural details of foliar burn in citrus. LM examination of the burned leaf area showed collapsed adaxial and abaxial epidermal cells and plasmolysis of mesophyll cells that created large intercellular spaces. SEM showed wrinkling of both the adaxial and abaxial epidermal cells. TEM revealed cytoplasmic vacuolation, disruption of cellular membrane, degradation of grana, and appearance of large plastoglobuli, implying loss of physiological activity. In contrast, control leaves had turgid adaxial and abaxial epidermal cells and compact mesophyll cells with few intercellular air spaces.

Open access

Joseph Uhring

Abstract

Anatomical observations were made on 2 petunia cultivars of Petunia hybrida Vilm., one ozone and sulfur dioxide susceptible and the other moderately tolerant with leaf cross and paradermal sections made from collections taken 4 hours to 30 days following fumigation. Disintegration of the circular chloroplast bodies into one homogenous mass was the first visible symptom of internal cell damage. Initially, O3 affected chloroplasts in palisade cells while SO2 affected chloroplasts in spongy cells. Plasmolysis, aggregation of cytoplasmic contents, and disintegration of nuclei occurred. Damage from SO2 proceeded more rapidly and was more extensive than that from O3; all cell components were destroyed over larger areas. Foliar sprays of succinic acid-2,2-dimethyl-hydrazide (daminozide) or benomyl soil drenches were applied 1 week before fumigation. Microscopic observations indicated that mesophyll tissue in both daminozide and benomyl treatments resembled to some degree the compact tissue typical of young, insensitive leaves.