Search

Postharvest assessment of 'Hass' avocado fruit ripening is frequently monitored by the fruit texture as it changes from hard to soft and 'buttery'. This large change in texture is easily measured, commonly by a penetrometer after removal of a small area of skin or by a whole-fruit compression measurement. The penetrometer is slow and destructive whereas the compression measurement is rapid and may be considered as non-destructive depending on the method. Investigation of the two methods on the same batch of fruit reveals information pertinent to the understanding of fruit ripening — beyond the simple provision of a numerical assessment of the progress of ripening. Monitoring of fruit under drying conditions revealed the role that fruit turgor plays in the compression measurement, and how it contributes to our understanding of the numerical values. Likewise, the observed variation among individual fruit ripening times may mean that averaged values are misleading, suggesting that fruit ripening takes longer than it actually does. The key element in the fruit-to-fruit variability was the pre-climacteric period before the fruit ripened. Additional penetrometer measurements of five regions of the fruit flesh for each fruit assessed quantified differences in mesocarp softening within the fruit. [ABSTRACT FROM AUTHOR]

Functional modifications in three populations of Fimbristylis complanata collected from differently salt effected habitats were evaluated. The populations were established in pots and treated with five NaCl levels (0, 100, 200, 300, and 400 mM). Population SH (collected from the highest salinities, ECe 37.94 dS m−1) exhibited better osmotic adjustment because of the higher accumulation of organic osmolytes under high salinities and was ranked as highly tolerant. Other features like an increased concentration of chlorophyll pigments ensured maintenance of photosynthetic capability, and accumulated higher K+ and Ca2+ contents that minimized the toxic effect of Na+ and maintained ion homeostasis. Salinity tolerance in the Lillah–Khewra foothills (LR) population (collected from moderately saline site, ECe 31.36 dS m−1) relied on the maintenance of shoot dry weight (SDW) and shoot and root length (RL) with a parallel accumulation of organic osmolytes and shoot Ca2+. This species is a stem succulent and can store excessive amount of salt in storage parenchyma, as indicated by the accumulation of high concentration of Na+ in shoot. The SH population, in particular, can be rated as the best for phytoremediation of salt-affected soils that accumulated more Na+ than other populations and concentration of osmolytes for turgor maintenance under high salinities. Novelty statementFimbristylis is less explored, particularly no information available on salt tolerance of F. complanata exists in the literature. [ABSTRACT FROM AUTHOR]

Skin aging is a multifactorial process consisting of two distinct and independent mechanisms: intrinsic and extrinsic aging. Youthful skin retains its turgor, resilience and pliability, among others, due to its high content of water. Daily external injury, in addition to the normal process of aging, causes loss of moisture. The key molecule involved in skin moisture is hyaluronic acid (HA) that has unique capacity in retaining water. There are multiple sites for the control of HA synthesis, deposition, cell and protein association and degradation, reflecting the complexity of HA metabolism. The enzymes that synthesize or catabolize HA and HA receptors responsible for many of the functions of HA are all multigene families with distinct patterns of tissue expression. Understanding the metabolism of HA in the different layers of the skin and the interactions of HA with other skin components will facilitate the ability to modulate skin moisture in a rational manner. [ABSTRACT FROM AUTHOR]

The effects of arsenate and arsenite on growth and transpiration were investigated in cucumber plants grown in nutrient solution containing 2, 10, and 100 μM phosphate, respectively. Root and shoot growth decreased by 48-64% compared to the control in all treatments and there was no significant difference between the effects of arsenic As(V) and As(III) except for the lowest phosphate concentration. At 2 μM phosphate As(III) had significantly higher growth inhibition than As(V). The inhibition of transpiration was between 46-68% in all treatments, and As(V) had stronger effect at 10 μM phosphate compared to 100 μM. Arsenic caused fast wilting 2 hours after the commencement of the treatment. However, the formation of adventitious roots prevented the loss of turgor. The hypothesis that aquaporins might be involved in the action of As(V) has been tested by comparison of the effect of As(V) and Hg, the inhibitor of aquaporins. Both treatments resulted in similar inhibition of growth and transpiration, increase in water saturation deficit and decrease in root exudation. Data imply that (i) phosphate reduces arsenate uptake, (ii) arsenate can be at least partially detoxified in cucumber at higher phosphate concentrations, (iii) arsenate may be reduced to arsenite and (iv) As(V) may interfere with the proper functioning of aquaporins. [ABSTRACT FROM AUTHOR]

The efficacy of different fertiliser levels was evaluated in terms of plant growth, plant shape, and leaf quality. Experiments were conducted on two cultivars of Aechmea of known sensitivity (high and low, respectively) to physiological leaf damage. Plants were grown under two fertiliser levels (a fertigation solution of 1.2 mS cm-1, or a fertigation solution of 2.4 mS cm-1) over a 9-month treatment period. In general, the lower level of fertiliser resulted in more desirable, compact plants, with leaf length as the major parameter determining plant shape. The higher level of fertiliser improved the growth rate significantly, but also increased the risk of leaf quality problems. The extent of this effect was strongly cultivar-dependent. In practice, growers will have to compromise between plant shape and leaf quality on the one hand, and growth rate on the other. Based on this work, either of two plant-related parameters can be used to evaluate the risk of leaf quality problems when changing fertiliser levels: (i) chlorenchymal cell dimensions at the leaf anatomical level, or (ii) turgor pressure at the leaf physiological level. [ABSTRACT FROM AUTHOR]

Monoclea forsteri Hook. is a thalloid liverwort species that is found in damp habitats and can, therefore, be expected to be sensitive to dehydration. It does, however, have some unique chemical constituents and anatomical features that could play a role in dealing with the adverse effects of water deficits. Corresponding to the habitat, M. forsteri lost its turgor at high relative water content (RWC≈0.90) and did not survive drying below 20% RWC. Moreover, the gametophytes showed an increase in malondialdehyde content and a depletion of the ascorbate pool during dehydration, indicating oxidative damage. Cellular constituents did not affect turgor pressure during drying and electrolyte leakage from the cells was greatly increased at RWC<0.20. Photosynthetic processes seemed not to be affected by the loss of turgor, but a decline appeared to correlate with an increase in electrolyte leakage. A speedy and fully sustained recovery from dehydration was realized from water contents above 30% and seemed only to be possible if membrane integrity could be preserved. Anatomical characteristics within M. forsteri gametophytes deserve further investigation to better understand their physiological functions. [ABSTRACT FROM AUTHOR]

The method of penetration of fungi through the host cuticle by means of cutinase versus mechanical pressure exerted by melanized appresoria has been the subject of debate. Colletotrichum kahawae Bridge & Waller infects green coffee berries in Africa, inducing 70-80% losses. Turgor pressure (TP) of the appresoria was estimated in vitro to be 2.6 MPa, about twice the osmotic pressure (OP) of the green berries. Appresoria exposed in vitro to polyethylene glycol (PEG) solution with OPs of 7.0 MPa and above immediately collapsed. However, collapsed appresoria subjected to OP as high as 46.5 MPa could recover. Green berries inoculated with conidial suspensions, if subjected to OP of 28.5 MPa, showed 7% of them with necrotic lesions. Total inhibition of infection was achieved at 46.5 MPa. The OP of PEG solutions applied to inoculated green fruit decreased to the OP of the green berries in 48 h. The resistance of appresoria to osmotic stress, combined with the rapid dilution of PEG by solutes (water) from the fruit might explain the rate of infection even at very high OR Unmelanized appresoria induced by tricyclazole showed TPs as low as one-quarter of melanized ones and, as a consequence, the percentage of infection on leaves and green berries was much lower. Cutinase was present in conidial mucilage and in extracellular fluids of germinated conidia in vitro and in planta. Cutinase was induced by growing the fungus in Czapek-Dox medium if cutin was used as the sole carbon source. Diisopropyl fluorophosphate, a cutinase inhibitor, totally inhibited cutinase activity of culture filtrates and extracellular fluids but did not prevent infection. It is suggested that the TP of C. kahawae appresoria might play a major role in coffee cuticle penetration, according to our results. [ABSTRACT FROM AUTHOR]

The scope of this review is limited to hormonal involvement in the induction of woody bud endodormancy and does not address dormancy maintenance or release. Knowledge of hormonal regulation of processes has become increasingly more complex, particularly with recent findings of auxin- and ethylene-triggered abscisic acid induction revealing many more responses mediated by ABA than originally considered. The intent of this review is to provide an account of the current state of knowledge of hormones in bud dormancy research within an historical context with a focus on promising avenues of research. While hormones are undoubtedly involved at some point during dormancy induction, meaningful progress in unraveling the mechanism of endo-dormancy-induction is difficult through this hormone-centered approach. The path to dormancy acquisition is a continuum. In many plants, this path begins far earlier than the traditionally-examined autumn period. Aside from more useful hormonal localization studies within the bud and utilization of mutants, continued gross analysis of hormone presence/absence during dormancy induction may not be fruitful. Examining the regulation of the early molecular switch within key cells of the apical meristem or subtending tissues may provide greater insight into dormancy induction. Turgor pressure-dependent cellular differentiation within the apical meristem and the extrinsic and intrinsic factors regulating turgor may be central to that molecular switch. Simpler model systems may need to be utilized to test these hypotheses. Only then can the potential role of hormones in endodormancy induction be more clearly articulated. [ABSTRACT FROM AUTHOR]