Describing Ordinal Odds Ratios for Stratified r × c Tables

For an r × ctable with ordinal responses, odds ratios are commonly used to describe the relationship between the row and column variables. This article shows two types of ordinal odds ratios where local‐global odds ratios are used to compare several groups on a c‐category ordinal response and a global odds ratio is used to measure the global association between a pair of ordinal responses. When there is a stratification factor, we consider Mantel‐Haenszel (MH) type estimators of these odds ratios to summarize the association from several strata. Like the ordinary MH estimator of the common odds ratio for several 2 × 2 contingency tables, the estimators are used when the association is not expected to vary drastically among the strata. Also, the estimators are consistent under the ordinary asymptotic framework in which the number of strata is fixed and also under sparse asymptotics in which the number of strata grows with the sample size. Compared to the maximum likelihood estimators, simulations find that the MH type estimators perform better especially when each stratum has few observations. This article provides variances and covariances formulae for the local‐global odds ratios estimators and applies the bootstrap method to obtain a standard error for the global odds ratio estimator. At the end, we discuss possible ways of testing the homogeneity assumption.     

The effect of salty diets and gradual transfer to sea water on osmotic adaptation, gill Na+, K+-ATPase activation, and survival of brook charr, Salvelinus fontinalis, Mitchill

The intensity and duration of the period of osmotic disturbance during introduction of brook charr into sea water were decreased by introducing the fish according to a gradient of salinity over a period of 6 days. Survival in summer increased from 25 to 90% with the use of a salinity gradient. However, kinetics and levels of activation of the gill Na⁺, K⁺-ATPase were not affected by the mode used for introducing brook charr into sea water. Neither was its level of activity modified by the use of a salted diet when the fish were in fresh water. The addition of 8 and 12% of salt to the diet prevented the plasma electrolyte surge of concentrations during the first days in sea water. In very cold water, survival rate was also drastically improved by giving an 8% salted diet during the 6 weeks preceding the introduction into sea water. These results show that both salty diets and exposure to brackish water during 6 days help brook charr face osmotic stress and improve their survival rate when introduced into full-strength sea water. The combined use of these preconditioning strategies might facilitate rearing this species in sea cages or silos.     

Estimating woody and herbaceous vegetation cover from time series satellite observations

In this paper we test a method to estimate the tree and grass vegetation cover over Australia from satellite-derived normalized difference vegetation index (NDVI) time series (monthly 1981–91, ≈5 km pixels) observations. The evergreen cover is assumed to track along the base of the NDVI time series, which is assumed to be equivalent to the woody vegetation cover. The base of the NDVI time series is estimated using modifications to a classical econometric model (i.e. time series is the sum of trend, seasonal and random components). Estimates of the average evergreen component during 1982–85 and 1986–89 were generally consistent with known vegetation distributions. Changes in evergreen cover were largely restricted to the south-west and south-east of Australia. Those changes were largely the result of differences in rainfall between the two periods. The proposed method for estimating woody vegetation cover is found to be generally robust. However, there are some regions where the grass (or pasture) is mostly evergreen. Some possible refinements are proposed to handle such cases.     

Changes in hydraulic conductance of citrus trees following a reduction in wetted soil volume

Abstract The effcct of the transition from fully to partially wetted soil voluine on transpiration rate and hydraulic conductance of mature citrus trees was examined in a 23-year-old, coninicrcial, sprinklerirrigated, Shanio u t i orange orchard. I rriga t i on frequency was determined by the rate of water loss from the soil, a s measured by neutron probes. The hydraulic conductance of tlic tree was coniputed from the rclationship between sap flow i n the trunk and leaf water potential. The diurnal valucs of leaf water potential and sap flow shifted towards lower levels as tlie water stored in the root zone was depleted. In the fully wetted soil volume the tree hydraulic conductance remained constant throughout the irrigation period, from June to Novcniber. However, partial wetting of the soil volume (40%) caused a reduction in the hydraulic conductance of the tree. Tlie decreased hydraulic conductance is attributed to tlie permanent interruption of water transport in part of tlie root system. Tlie rcsults of tlie experiment suggest that despite tlie increase of irrigation frequency, partial wetting intensifies water stress in tlie trees.     

Suberin lamellae in the hypodermis of maize (Zea mays) roots; development and factors affecting the permeability of hypodermal layers

Abstract The development of suberin lamellae in the hypodermis of Zea mays cv. LG 11 was observed by electron microscopy and the presence of suberin inferred from autoliuorescence and by Sudan black B staining in nodal (adventitious) and primary (seminal) root axes. Suberin lamellae were evident at a distance of 30–50 mm from the tip of roots growing at 20°C and became more prominent with distance from the tip. Both oxygen deficiency and growth at 13°C produced shorter roots in which the hypodermis was suberized closer to the root tip. There were no suberin lamellae in epidermal cells or cortical collenchyma adjacent to the hypodermis. Plasmodesmata were not occluded by the suberin lamellae: there were twice as many of them in the inner tangential hypodermal wall (1,14 μn^?2) as in the junction between the epidermis and hypodermis (0.54 μm^?2). Water uptake by seminal axes (measured by micropotometry) was greater at distances more than 100 mm from the root lip than in the apical zone where the hypodermis was unsuberized. In the more mature zones of roots grown at 13°C rates of water uptake were greater than in roots grown at 20°C even though hypodermal suberization was more marked. Sleeves of epidermal/hypodermal cells (plus some accessory collenchyma) were isolated from the basal 60 mm of nodal axes by enzymatic digestion (drisclase). The roots were either kept totally immersed in culture solution or had the basal 50 mm exposed to moist air above the solution surface. In both treatments the permeabilities to tritiated water and ₈₆Rb were low (circa 10^?5mms^?1) in sleeves isolated from the extreme base. In roots grown totally immersed, however, the permeability of sleeves increased 10 to 50-fold over a distance of 40 mm. In roots exposed to moist air the permeability remained at a low level until the point where the root entered the culture solution and then increased rapidly (> 50-fold in a distance of 8 mm). Growth of roots in oxygen depleted (5% O₂) solutions promoted the development of extensive cortical aerenchymas. These developments were not associated with any reduction in permeability of sleeves isolated from the basal 40 mm of the axis. It was concluded that the presence of suberin lamellae in hypodermal walls does not necessarily indicate low permeability of cells or tissues to water or solutes. The properties of the walls (lamellae?) can be greatly changed by exposure to moist air, perhaps due to increased oxygen availability.     

Sodium-induced calcium deficiency in salt-stressed corn

Abstract The effect of the Na⁺/Ca²⁺ ratio in the root media on salt-stressed corn (Zea mays L. cvs DeKalb XL-75 and Pioneer 3906) was determined in greenhouse experiments. Plants grown in a complete nutrient solution salinized with 86.5 mol m^?3 NaCl exhibited severe Ca²⁺ deficiency symptoms at the four-leaf stage. The symptoms disappeared when part of the NaCl was replaced with 10 mol m^?3 CaCl₂ (Na⁺/Ca²⁺ molar ratio = 5.7). Salt stress at an iso-osmotic potential of ?0.4 MPa substantially decreased shoot growth at all solution Na⁺/Ca²⁺ ratios from 34.6 to 0.26. However, the dry weights of blades at 26 d of age were much less when plants were salinized with NaCl alone, particularly that of DeKalb XL-75 which was more susceptible to Na-induced Ca²⁺ deficiency than was Pioneer 3906. The growth of sheaths was similarity reduced by sail stress at all Na⁺/Ca²⁺ ratios. The symptoms of Ca²⁺ deficiency were correlated with low Ca²⁺ concentrations in the leaf tissue. Ca²⁺ concentrations in the developing blades of NaCl-stressed plants were much lower than in control plants. As the Na⁺/Ca²⁺ ratio in the solution was decreased, Ca²⁺ levels increased in both the blades and sheaths while Na⁺ concentrations greatly decreased. DeKalb XL-75 was much less effective than Pioneer 3906 in restricting the uptake of Na⁺. The results clearly indicate that NaCl stress may cause lesions and unique plant responses that are not manifested on agronomic plants grown on saline soils.     

Stomatal behaviour and leaf water potential of chilled and water-stressed Solanum melongena, as influenced by growth history

Abstract Leaf diffusion resistance and leaf water potential of intact Solanum melongena plants were measured during a period of chilling at 6 °C. Two pretreatments, consisting of a period of water stress or a foliar spraying of abscisic acid (ABA), were imposed upon the plants prior to chilling. The control plants did not receive a pretreatment. In addition to intact plant studies, stomatal responses to water loss and exogenous abscisic acid were investigated using excised leaves, and the influence of the pretreatment observed. Chilled, control plants wilted slowly and maintained open stomata despite a decline in leaf water potential to –2.2 MPa after 2 d of chilling. In contrast plants that had been water stressed or had been sprayed with abscisic acid, prior to chilling, did not wilt and maintained a higher leaf water potential and a greater leaf diffusion resistance. In plants that had not received a pretreatment, abscisic acid caused stomatal closure at 35 °C, but at 6°C it did not influence stomatal aperture. The two pretreatments greatly increased stomatal sensitivity to both exogenous ABA and water stress, at both temperatures. Stomatal response to water loss from excised leaves was greatly reduced at 6°C. These results are discussed in relation to low temperature effects on stomata and the influence of preconditioning upon plant water relations.     

Early stomatal closure in waterlogged pea plants is mediated by abscisic acid in the absence of foliar water deficits

Abstract Soil waterlogging decreased leaf conductance (interpreted as stomatal closure) of vegetative pea plants (Pisuin sativum L. cv. ‘Sprite’) approximately 24 h after the start of flooding, i.e. from the beginning of the second 16 h-long photo-period. Both adaxial and abaxial surfaces of leaves of various ages and the stipules were affected. Stomatal closure was sustained for at least 3 d with no decrease in foliar hydration measured as water content per unit area, leaf water potential or leaf water saturation deficit. Instead, leaves became increasingly hydrated in association with slower transpiration. These changes in the waterlogged plants over 3 d were accompanied by up to 10-fold increases in the concentration of endogenous abscisic acid (ABA). Waterlogging also increased foliar hydration and ABA concentrations in the dark. Leaves detached from non-waterlogged plants and maintained in vials of water for up to 3 d behaved in a similar way to leaves on flooded plants, i.e. stomata closed in the absence of a water deficit but in association with increased ABA content. Applying ABA through the transpiration stream to freshly detached leaflets partially closed stomata within 15 min. The extractable concentrations of ABA associated with this closure were similar to those found in flooded plants. When an ABA-deficient ‘wilty’ mutant of pea was waterlogged, the extent of stomatal closure was less pronounced than that in ordinary non-mutant plants, and the associated increase in foliar ABA was correspondingly smaller. Similarly, waterlogging closed stomata of tomato plants within 24 h, but no such closure was seen in ‘flacca’, a corresponding ABA-deficient mutant. The results provide an example of stomatal closure brought about by stress in the root environment in the absence of water deficiency. The correlative factor operating between the roots and shoots appeared to be an inhibition of ABA transport out of the shoots of flooded plants, causing the hormone to accumulate in the leaves.     

Studies on the protolytic reactions coupled with water cleavage in photosystem II membrane fragments from spinach

The protolytic reactions of PSII membrane fragments were analyzed by measurements of absorption changes of the water soluble indicator dye bromocresol purple induced by a train of 10 s flashes in dark-adapted samples. It was found that: a) in the first flash a rapid H⁺-release takes place followed by a slower H⁺-uptake. The deprotonation is insensitive to DCMU but is completely eliminated by linolenic acid treatment of the samples; b) the extent of the H⁺-uptake in the first flash depends on the redox potential of the suspension. In this time domain no H⁺-uptake is observed in the subsequent flashes; c) the extent of the H⁺-release as a function of the flash number in the sequence exhibits a characteristic oscillation pattern. Multiphasic release kinetics are observed. The oscillation pattern can be satisfactorily described by a 1, 0, 1, 2 stoichiometry for the redox transitions S_i S_i+1 (i=0, 1, 2, 3) in the water oxidizing enzyme system Y. The H⁺-uptake after the first flash is assumed to be a consequence of the very fast reduction of oxidized Q₄₀₀(Fe³⁺) formed due to dark incubation with K₃[Fe(CN)₆]. The possible participation of component Z in the deprotonation reactions at the PSII donor side is discussed.Abbreviations A protonizable group at the PSII acceptor side - BCP Bromocresol Purple - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - FWHM Full Width at Half Maximum - Q_A, Q_B primary and secondary plastoquinone at PSII acceptor side - Q₄₀₀ redox group at PSII-acceptor side (high spin Fe²⁺) - P680 Photoactive chlorophyll of PSII reaction center - S_i redox states of the catalytic site of water oxidation - Z redox component connecting the catalytic site of water oxidation with the reaction center