Evaluation of plant-based water status indicators in mature apple trees under field conditions

The performance of different indicators of plant water status as a tool for irrigation management was evaluated in mature field grown ‘Golden Delicious’ apple trees during the late summer of 1998. Control (C) and stress (S) treatments were studied. In the C treatment trees were irrigated daily at 100% ET_c whereas in the S treatment water was withheld during 31 days (DOY’s 236–266). Predawn water potential (Ψ_pd) and midday stem water potential (Ψ_stem) were measured several times a week during the experimental period. Three daily measurements of stomatal conductance (g_s) and stem water potential were made during five consecutive days in mid-September. Trunk diameter changes (TDC) were recorded by LVDT sensors, and from these measurements, maximum daily shrinkage (MDS), daily growth (DG), and cumulative growth (CG) were calculated. Midday Ψ_stem showed the best ratio between the response to moderate water stress and tree variability (“signal/noise” ratio) among the indicators studied here, followed closely by Ψ_pd. On the other hand, the poorest water status indicator was g_s. Due to the low trunk growth rate of the trees, and its high variability, DG and CG were not adequate indicators. MDS showed a lower sensitivity to water stress and a higher variability (CV = 0.19) than midday Ψ_stem (CV = 0.08) and Ψ_pd (CV = 0.10). However, MDS correlated well with ET₀ and with midday Ψ_stem (R ² = 0.79) thus, making this parameter an interesting and promising tool for irrigation management in apple orchards. More research needs to be done in order to define reference values for MDS and plant water potential indicators, in relation to evaporative conditions and in different phenological periods, and to quantify the relationship between water status indicators values and apple tree yield and fruit quality.     

A simple and efficient cryopreservation of in vitro-grown shoot tips of `Troyer' citrange [Poncirus trifoliata (L.) Raf. × Citrus sinensis (L.) Osbeck.] by encapsulation-vitrification

Wheat of two strong high-protein and two weak low-protein cultivars from New Zealand and Australia were milled to commercial specifications. All millstreams were tested for α-amylase, β-amylase, falling number, protein, starch, damaged starch, amylose, amylopectin, pentosan and ash. The distribution of β-amylase in millstream flours was more variable among cultivars than α-amylase. Generally, both enzymes had lowest activity in sizing and early reduction flours. α-Amylase was very high in the bran, pollard and germ fractions, in which ash content was very high, whereas β-amylase was low in these fractions. These observations, together with the moderate correlation of α-amylase and poor correlation of β-amylase to ash content, suggest that most α-amylasein flour derives from contamination with bran, pollard and germ, whereas most β-amylase derives from the endosperm. Falling numbers varied between the cultivars, but variation amongst millstreams for each cultivar was low, except for cv. Frame, which had particularly high falling number values (834 and 1197) in second and third break flours. These two flours had some of the highest α-amylase levels and lowest starch levels. However, they also had very high protein content (22 and 26%) and very low starch damage (3.2 and 4.5%), which may contribute to the high falling numbers. When endogenous α-amylase in the flour with the highest falling number was supplemented with high levels of barleyα-amylase, the flour withstood the detrimental effects of α-amylasein baking (sticky crumb, poor crumb texture and loaf volume) better than flours of lower falling number, but did not withstand the effects ofα-amylase on falling number. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effect of Cadmium and Iron on Rice (Oryza Sativa L.) Plant in Chelator-Buffered Nutrient Solution

ABSTRACT

To better understand the mechanisms responsible for differences in uptake and distribution of cadmium (Cd), nutrient-solution experiments were conducted with different varieties of rice (Oryza sativa), ‘Khitish’ and ‘CNRH3’. The plants were grown in a complete nutrient solution with different levels of pCd (-log free Cd⁺² activity) and pFe [-log free iron (Fe⁺²) activity]. The required concentrations of chelating agent and metals were determined using a computerized chemical equilibrium model such as Geochem-PC. Experimental treatments included a combination of four pCd activity levels (0, 7.9, 8.2, and 8.5) applied as Cd (NO₃)₂ 4H₂O, and two pFe activity levels (17.0 and 17.8) applied as FeCl₃. The application of both Cd and Fe in solution culture significantly affected plant growth, yield, and Cd accumulation in plant tissue. In general, yield of rice was decreased by an increase in amount of solution Cd; however, yield response varied among the cultivars. At the 7.9 pCd level, yields of rice cultivars ‘Khitish’ and ‘CNRH3’ were reduced to 69% and 65%, respectively, compared with control plants. Root Cd concentrations ranged from 2.6 mg kg^?1 (control plants) to 505.7 mg kg^?1 and were directly related to solution Cd concentrations. In rice plants, Cd toxicity symptoms resembled Fe chlorosis. Differential tolerance of varieties to phytotoxicity was not readily visible, but a significant interaction of substrate Cd and variety was obtained from dry-matter yields. Significant interactions indicated that response of tissue Cd concentration, plant Cd uptake, and translocation of Cd to the aerial parts were dependent on variety as well as substrate Cd. Uptake of Cd by roots was significantly higher than by shoots. Higher Cd uptake by rice plants decreased the uptake of other beneficial metals.

The effect of Cd and Fe on the rate of phytometallophore release was also studied in the nutrient solution. Among the rice genotypes, ‘Khitish’ was the most sensitive to Cd toxicity. In both genotypes, with the onset of visual Cd-toxicity symptoms, the release of phytometallophore (PM) was enhanced. Among the rice varieties, ‘Khitish’ had the highest rate of PM release. Treatments with the metal ions studied produced a decrease in chlorophyll and enzyme activity. A decrease in concentrations of chlorophyll pigments in the third leaf was observed due to the highest activity level of Cd (pCd 7.9). Activities of enzymes such as peroxidase (POD) and superoxide dismutase (SOD) are altered by toxic amounts of Cd. Changes in enzyme activities occurred at the lowest activity of Cd (pCd 8.5) in solution. Peroxidase activity increased in the third leaf. Results showed that in contrast with growth parameters, the measurements of enzyme activities may be included as early biomarkers in a plant bioassay to assess the phytotoxicity of Cd-contaminated solution on rice plants. Evidence that Cd uptake and translocation are genetically controlled warrants the selection of varieties that assimilate the least Cd and that translocate the least metal to the plant part to be used for human and animal consumption.     

Precision parameters of methods of analysis required for nutrition labeling. Part I. Major nutrients

Major components of foods and feeds are fat, protein, and carbohydrates. Fat and protein are determined by direct measurements that are interpreted as the quantity of the constituent. Carbohydrates are usually calculated by difference. For this calculation, values for moisture/solids, ash, and "fiber" are also needed. The readily available collaborative studies for the determination of these major components are reviewed in an attempt to assign precision parameters to validated methods of analysis. When a number of studies for the same analyte, in the same food, by the same method are available, it is seen that the precision parameters among laboratories (standard deviations, SR; relative standard deviations, RSDR) and the ISO maximum tolerable difference functions (repeatability value, r; reproducibility value, R) are not characterized by any conventional distribution. The precision data are best summarized as a median or average parameter and the interval containing the centermost 90% of reported values. Typically, the precision of methods of analysis can be expressed as a function of concentration only, independent of analyte, matrix, and method. The average RSDR value from each collaborative data set can then be used as the numerator in a ratio containing, as the denominator, the value calculated from the Horwitz equation: RSDR = 2 exp (1 - 0.5 log C) where C is the concentration as a decimal fraction. A series of ratios consistently above 1, and especially above 2, probably indicates that a method is unacceptable with respect to precision. By this criterion, only the protein (Kjeldahl) determination is unqualifiedly acceptable with a 90% interval for RSDR of 1 to 3% at C values above about 0.01 (1 g/100 g). Fat, moisture/solids, and ash are acceptable down to limiting concentrations in the region of 1 to 5 g/100 g, if a test portion large enough to provide at least 50 mg of weighable residue or volatiles is specified. Measurements of individual carbohydrates and fiber-related analytes have unexpectedly poor precisions among laboratories. The variability, although high, may still be suitable for nutrition labeling. Reliability of analyses for the control of labeling of the primary nutrients must be achieved through quality assurance programs that require strict adherence to the directions of empirical methods and the use of suitable reference materials for absolute methods.     

Pottery manufacture in early Roman Galilee: a micromorphological study

The characteristics of, and the sources of the soil materials for, pottery groups manufactured in three ancient settlements of early Roman (late first century BC–first century AD) Galilee were studied by micromorphological techniques. The site-specific manufacturing proveniences of the three respective pottery groups have been previously demonstrated by chemical analysis. One of the sites, Kefar Hananya, is located near the geographical boundary between the Upper and Lower Galilee while the other two, Shikhin and Yodefat, are in the Lower Galilee. Each of the settlements made pottery from different soil types. In one case (Yodefat) temper was added to the main soil material. The Kefar Hananya pottery was made from noncalcareous Red Mediterranean soils (Terra-Rossa soil type) derived from hard limestone. Although most of the soils in the Galilee derive from Upper Cretaceous geological formations, the Kefar Hananya pottery was prepared from soils, found near that settlement, that were derived from Lower Cretaceous material rich in the kaolinite clay mineral. Micromorphological analysis of 41 randomly selected samples of the most common early Roman storage jar type thought to have been produced at Shikhin showed that all of the vessels were made from one of three soil types, Colluvial–Alluvial soils, Brown Grumusols, or Pale Rendzina. Study of the lithology and soils in the area of Shikhin showed that all three soil types derive from soil material eroded from the hilly area, on which the ancient settlement of Shikhin was built, into the adjacent valleys below the site. Samples of the Shikhin pottery group collected on the surface, in contrast with excavated samples, exhibit postdepositional carbonate infilling by dissolution and reprecipitation of the carbonates due to repeated exposure to water. No added temper was used for the preparation of either the Kefar Hananya or the Shikhin pottery groups. The Yodefat pottery, made from Rendzinic material rich in calcareous material, is of particular interest. This soil material contains about 70–80% calcareous material homogeneously mixed with the clayey plasma. In order to diminish the effect of the large amount of calcareous material and improve the properties of this raw material for pottery manufacture, leached clayey soil material of Terra-Rossa soil type was added as temper. The micromorphological comparison of the pottery groups and soil materials shows that two main factors influenced the raw-material procurement strategies of the potters of these settlements: the proximity of the soil material to the potters' settlement, and the suitability of the soil material for pottery manufacture.     

Understory structure and function following release from cattle grazing and overstory thinning in Mediterranean conifer plantations

Key message

Cattle grazing and overstory cover restrict understory growth and interact in shaping the understory community structure in Mediterranean conifer plantations.

Context

Understanding how silvicultural manipulations drive understory structure and function in Mediterranean pine plantations is essential for their multifunctional management.

Aims

This paper aims to study the interactive effects of cattle grazing and overstory thinning on understory structure and function.

Methods

Ten plots (0.25 ha) were selected in East Mediterranean mature Pinus brutia plantation (rainfall = 600 mm year^?1) representing thinned (≈100 trees ha^?1, leaf area index (LAI) ≈ 1.6) and non-thinned (≈230 trees ha^?1, LAI ≈ 3.5) areas. Two subplots (100 m²) within each plot were fenced in 2000 and 2006 while a third one remained grazed. Understory growth and species composition were measured in 2010.

Results

Thinning and grazing exclusion both positively influenced woody growth with their combined effect during 10 years leading to 20-fold increase in vegetation volume. An increase (15-fold) in herbaceous biomass was recorded 4 years after grazing exclusion but disappeared 10 years after exclusion due to increased woody cover. Species richness was not influenced by grazing but was positively affected by thinning. Understory composition was affected by grazing × thinning interaction with herbaceous ephemerals and short woody species being more frequent in grazed, thinned areas while larger woody species were more associated with ungrazed, non-thinned areas.

Conclusion

Grazing impacts on forest understories depend on overstory cover. We propose variable grazing-thinning combinations to meet multiple management objectives.

     

The cholinergic synapse and the site of memory

A simple hypothesis can explain the results obtained to date if we disregard those results when we wait 30 minutes after original learning to inject. The hypothesis is that, as a result of learning, the postsynaptic endings at a specific set of synapses become more sensitive to transmitter. This sensitivity increases with time after initial learning and then declines. The rate at which such sensitivity increases depends on the amount of initial learning. If the curve of transmission plotted against time is displaced upward with anticholinesterases then the very low portions will show facilitation, and the high portions will cause block (Fig. 8). The middle portions will appear unaffected (unless special experimental tests are made). If the curve of transmission is displaced down with anticholinergics, then the middle portion will appear unaffected and only the very early or late components will show block. The results are evidence that synaptic conductance is altered as a result of learning. So far it seems (i) that cholinergic synapses are modified as a result of learning and that it probably is the postsynaptic membrane that becomes increasingly more sensitive to acetylcholine with time after learning, up to a certain point. (ii) After this point, sensitivity declines, leading to the phenomenon of forgetting. (iii) There is also good evidence that there is an initial phase of declining sensitivity to cholinesterase or increasing sensitivity to anticholinergics. This could reflect the existence of a parallel set of synapses with fast decay that serve as a shortterm store. (iv) Increasing the amount of learning leads to an increase in conductance in each of a set of synapses without an increase in their number. (v) Both original learning and extinction are subserved by cholinergic synapses.     

Foliar sprays of NPK fertilizers induce systemic protection againstPuccinia sorghi andExserohilum turcicum and growth response in maize

One spray of 0.1 M aqueous solutions of NPK fertilizers on the upper sides of maize leaves 1, 2, and 3, 2–4 h prior to inoculation, induced systemic resistance (ISR) against northern leaf blight (NLB) caused byExserohilum turcicum andPuccinia sorghi which were developed on leaves 4, 5, 6, and 7. ISR was expressed as a reduction in the number and area of lesions ofE. turcicum and in the number of sporulating or non-sporulating pustules ofP. sorghi on leaves 4, 5, 6, and 7. The reduction in the number of NLB lesions ranged from 51% (KH₂PO₄) to 69% (K₂HPO₄) and their size reduction ranged from 73% (KNO₃) to 91% (K₂HPO₄) as compared with water prayed plants. The reduction in the number of pustules ofP. sorghi ranged from 66 to 77%. Fertilizers consisting of various combinations of N, P and K in every case induce similar levels of protection in either host-pathogen system. The induced protection was evident regardless of the leaf position or the rate of NPK accumulation in the upper protected leaves. High fresh weight was detected in the induced plants which expressed the greatest induced protection against NLB and common rast. The possible dual use of NPK fertilizers — to supply nutrients to plants foliarly and at the same time to activate the mechanism(s) for induction of systemic protection toP. sorghi andE. turcicum in maize — is discussed.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel, No. 1315-E, 1995 series.     

Molecular mapping of QTL for southwestern corn borer resistance, plant height and flowering in tropical maize

Development of multiple insect resistance in tropical maize represents a major effort of the maize breeding programme at CIMMYT. Resistance to the southwestern corn borer (SWCB) is polygenically controlled with primarily additive gene action. Our main objective was to identify quantitative trait loci (QTL) involved in resistance to SWCB. Other objectives were to detect QTL in the same population for plant height, female flowering, and the anthesis-silking interval (ASI). A population of 472 F₂ individuals derived from a cross between the susceptible line Ki3 and the resistant inbred CML139, was restriction fragment length polymorphism (RFLP) genotyped using 110 maize probes. F₃ families were rated for leaf-feeding damage after artificial infestation at one location in three consecutive years. Height and flowering were measured in protected trials in two locations. QTL analyses were conducted using joint composite interval mapping. Seven QTL on chromosomes 3, 5, 6, 8, and 9 explained 30% of the phenotypic variance (σ²_p) for SWCB damage. Most QTL alleles conferring resistance were contributed from CML139. QTL showed dominance, partial dominance and additive gene action. Eleven QTL dispersed across the genome were determined to affect plant height and explained 43% of σ²_p. Four of these were in close proximity to loci with qualitative effects on plant height. Thirteen QTL (50% of sigma;²_p) were identified for days to female flowering and nine (30% of σ²_p) for ASI. Our results, along with those from other mapping studies at CIMMYT, are allowing us to formulate marker-assisted selection schemes to complement the breeding efforts for such complex traits as borer resistance.