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( Khanal et al. 2021 ; Winkler and Knoche 2021 ). An alternative explanation for neck shrivel is an asymmetric distribution of the osmotic potential (ψ Π ) within the plum tissues. Assuming the fruit to be at equilibrium water potential (ψ), a more

Open Access

The water potential (Ψ) of the sweet cherry fruit and its two components, osmotic potential (Ψ Π ) and turgor (Ψ P ) (where Ψ = Ψ Π + Ψ P ), are likely to be important factors affecting fruit cracking. First, fruit Ψ affects the rate of water

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Abstract

Water and turgor potentials of callus tissue from the cactus Echinopsis turbinata L. increased with increasing concentration of kinetin. Osmotic potential showed no consistent trend with an increase in concentration of kinetin or p-chlorophenoxyacetic acid (p-CPA).

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for tall fescue subjected to the 20% ETo irrigation level and lower at 20 d after treatment began for the 60% ETo irrigated level ( Table 1 ). Osmotic potential was lower in the 20% or 60% ETo treatment compared with the well-watered control on all

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The osmotic potential and development of apple and peach floral and vegetative buds and tissue were determined pre- and post-bloom. Apple and peach floral and vegetative buds were removed pre-bloom and the osmotic potential and bud development measured pre- and post-bloom. The osmotic potential of vegetative and floral buds was related to the phenology of bud development. Developing buds had a lower (more negative) osmotic potential than dormant buds. Removal of peach floral buds lowered osmotic potential and increased vegetative bud development and early leaf growth rate. Removal of peach vegetative buds, however, reduced fruit bud development, fruit growth, and embryo survival. Osmotic potential was an index of sink activity during the pre- and post-bloom stages of development.

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Absolute and relative fruit growth rates (AGR and RGR) of 5 cultivars were calculated from the oven-dry weights of fruits harvested periodically throughout the growing season. Both AGR and RGR were higher for larger fruit of different cultivars with similar days to maturity, and for summer- versus fall-ripening cultivars. Seasonal variability in AGR and RGR was observed, Apple fruit cortex disks were incubated in 14C-sorbitol solutions in vitro to determine if uptake rates at the cellular level varied between cultivars. Rates of sorbitol accumulation, expressed es μg sorbitol per mg dry weight cortex tissue, declined as the season progressed. Within a cuitivar, uptake rates were not relatad to fruit size, nor were differences found between cortex tissue samples from competing fruit on a spur. Sorbitol uptake rates were significantly lower for the more slowly-growing cultivar. The osmotic potential of the expressed cortex sap, sampled on several dates, was consistently lower for the more rapidly-growing cultivar. Thus, inherent differences in fruit growth rates among cultivars may be due to variation in regulation of osmotic potential.

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Abstract

Rhythmic pulses of irreversible petal expansion in rose (Rosa hybrida L. ‘Sonia’) petals cause diurnal changes in the rate of flower opening. Time-lapse cinematography revealed a transient increase in the rate of rose flower opening that commenced shortly before the onset of a light period and lasted for a few hours. Petal expansion, which occurred sequentially from the outer to the innermost whorl, involved rhythmic increases in fresh and dry weights. The amount of expansion was greatest in the distal portion of each petal and least near the petal base. Periods of rapid expansion were accompanied by decreases in starch and increases in soluble sugars in the petals, but the total carbohydrate content of the petals remained constant during a light–dark cycle. During expansion, the osmotic potential of the outer petal increased from −790 to −690 kPa. Starch hydrolysis during petal growth appears to be important for maintenance of cell size, but it is not the factor controlling cell expansion.

Open Access

Abstract

A seaweed extract (Cytex) was incorporated at 0%, 1%, 2%, and 3% (v/v) into four carrier gels used for fluid drilling. The gels were: magnesium silicate (Laponite), starch acrylate polymer (Liquagel), potassium copolymer (Viterra Agrigel), and a starch (Water lock B-100). When moisture was not lost, the pH values were significantly different among diluted gels (1 gel : 1 water, v/v) and ranged from 6.8 to 9.2. Incorporation of the seaweed extract significantly decreased the pH of the gels. Osmotic potential values of all the gels were close to 0 MPa, with potassium copolymer having a significantly lower osmotic potential (−0.03 MPa) than that of starch acrylate polymer (−0.007 MPa). Incorporation of the seaweed extract signficantly decreased the osmotic potential of the gels between −0.12 and −0.16 MPa. When gels were dehydrated to simulate water stress conditions (0% to 50% water evaporation), pH values were decreased further (ranging from 4.6 to 6.8). Osmotic potential decreased in all the gels to a range between −0.22 and −0.36 MPa with increasing moisture loss.

Open Access

Effects of reduced osmotic potential on somatic embryos of celery (Apium graveolens L.) were studied in an attempt to understand and improve their tolerance to partial desiccation. Embryos responded similarly to application of high osmoticum (384 mOs/kg H2O vs. 190 mOs/kg H2O in the control), achieved either by manipulation of sucrose or polyethylene glycol concentrations (PEG). Treatments of high osmotic concentration applied during the last 2 days of the embryo production cycle increased embryo survival and conversion after partial desiccation. The most striking effect of the high osmotic concentrations was the 4-fold increase in proline, while a 2-fold increase was obtained with 1 μm ABA alone. Application of high osmotica decreased reducing sugars, increased sucrose, but did not affect starch content of embryos; of these responses, only the change in sucrose was similar to that induced by ABA. Osmotic treatments did not affect total fatty acid content in the embryos compared to the 2-fold increase induced by ABA. Chemical name used: abscisic acid (ABA).

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Abstract

Tomato plants (Lycopersicon esculentum Mill.) were grown to maturity in complete nutrient solution with osmotic potentials (sψo) of −0.8, −2.4, −4.4 and −6.4 bars from NaCl additions, and 0.5, 5.0, and 50 ppm P as variables. The objectives were to evaluate the effects of sψo and P and their interactions with respect to fruit yield and quality, and nutrient concentrations in the plants and fruits. Reducing the sψo (increasing negative values) by NaCl addition significantly decreased tomato fruit yield, but increased the percentages of soluble solids, total solids, blossom-end rot (BER) incidence and non-marketable fruit. Increased solution salinity resulted in higher leaf concentrations of P, Na and Cl. Increased nutrient solution P levels (Ps) significantly increased fruit yield, but decreased the percentage of fruit soluble solids and BER incidence. Leaf P, Ca and Cl concentrations of plants grown in the high P nutrient solution were higher than those of the leaves from low P solution plants. The incidence of BER was greatest under low sψo and low Ps. Reduced Ca concentrations of leaves and mature fruit were associated with the BER development. The Ca concentration of mature normal fruit varied from 0.039 to 0.076% compared with 0.028 to 0.043% for mature BER fruit. Leaf Ca concentrations of 1.5 to 2.0% were associated with the BER condition.

Open Access