Controlled Environment Cabinets Research Articles

Micronutrients

Six wheat cultivars were grown in a controlled environment cabinet at 15C for up to 30 days in pots containing a manganese (Mn) deficient calcareous soil. Significant differences were found between cultivars for dry matter production, Mn concentration and Mn uptake with 10 or 50 mg k‐1 Mn added but not without added Mn. In contrast, cultivar differences were small for parameters associated with plant utilisation of Mn: chlorophyll a fluorescence induction kinetics (Fo, Fp, Fv, Fo/Fv and Fv/Fp), chlorophyll concentration and the critical Mn concentration for photosynthetic efficiency (as measured by Fv/Fp). The critical Mn concentration for Fv/Fp was approx. 13–15 μg g‐1, whilst that for relative shoot growth ranged from 12–17 μg g‐1.

Relationship between SO 2 dose and growth of the pea aphid, Acyrthosiphon pisum, on peas

A series of experiments was carried out in controlled environment cabinets to investigate the effects of SO 2 dose on the mean relative growth rate (MRGR) of pea aphids, Acyrthosiphon pisum, feeding on the pea plant, Pisum sativum. There was a significant linear increase in the MRGR of aphids feeding on SO 2-fumigated plants, relative to control aphids feeding on plants in charcoal-filtered air. The increase in MRGR reached a maximum of 11% at SO 2 concentrations between 90 and 110 nl litre −1. MRGR declined at higher SO 2 concentrations until above 220 nl litre −1 it was below that of the controls. The dose-response curve is discussed in relation to reported changes in the nitrogen metabolism of plants subject to air pollution, the response of aphids to host plant nitrogen and possible toxic effects of high concentrations of SO 2 on the aphid.

Paint testing: A survey of some modern techniques Part 6: Corrosion and weather resistance

Previous articles in this series have described some of the techniques that are used to characterise paint film properties. In many instances results from such tests are used predictively, that is they yield information on the likely performance of the coating during service. It is however, widely accepted that the most accurate way of determing performance is to actually subject the coating‐substrate combination to the service conditions it will meet in practice, or a close approximation to them. Suitability can then be assessed by periodic inspection and/or by taking measurements of some appropriate parameter which might be expected to change with time. A great many techniques have been developed and refined over the years that are intended to replicate service environments in some simplified and reproducible way; an indication of the range of test methods that can be employed to this end can be seen in a recent article by El‐Sawy. Many of these techniques are suitable for the laboratory and range from simple immersion tests in appropriate solutions through to exposure testing in controlled environment cabinets. Because of the problems of interpreting the results from laboratory simulation testing though, exposure of test panels in the natural environment is also widely practiced. This, the last article in this series, will consider some of the recent literature concerning environmental testing, with particular reference to techniques appropriate for assessing the weather, marine and corrosion resistance of coatings.

EXPERIMENTAL ANALYSIS OF FLUORIDE SUSCEPTIBILITY OF GRAPEVINE (VITIS VINIFERA L.): LEAF DEVELOPMENT DURING FOUR SUCCESSIVE SEASONS OF FUMIGATION

SUMMARYLeaf development was studied in potted specimens of grape vine (Vitis vinifera L., varieties Chardonnay, Gordo and Traminer) that were exposed to hydrogen fluoride in controlled environment cabinets during four successive growing seasons. The duration of exposures varied from 54 d in the second season to 159 d in the fourth. There was no significant or consistent effect of fluoride on the numbers of leaves produced on major or lateral shoots in any variety. Leaf size during the first growth flush of a season was not influenced by the present or previous exposure of plants to ambient fluoride concentrations up to 1.5μm F m−3. Mature leaf size during the middle or latter portion of the fourth season of fumigation was significantly reduced in the Chardonnay and Traminer varieties as a result of exposure to fluoride concentrations of 0.64μg m−3 or more. Leaf size in the variety Gordo was not affected by ambient fluoride concentrations up to 1.5μg F m−3. Stomatal frequency and size in the variety Chardonnay, and leaf water vapour conductance in all varieties were not affected by ambient fluoride concentrations up to 1.05μg F m−3. The work demonstrates variations in response of grape vine leaves to ambient conditions at different stages of the growing season.

The Effect of Strain of Rhizobium and of Temperature on Nodulation and Early Growth of Trifolium semipilosum

SUMMARYThe effect of strain of Rhizobium and of temperature on nodule formation and early growth of Trifolium semipilosum was studied in controlled environment cabinets. Time required for nodules to form was affected by strain of Rhizobium and by root temperature, acting independently. Strains CB788 and CB2116 required only 9.5 to 10.0 days, averaging over temperatures, whereas strains CB782 and CB526 required 12.8 to 13.0 days. Nodulation was earliest at whole-plant temperatures of 25/20°C and 30/25°C day/night (average 9.5 days); 15 days were required at 20/15°C. Nodule number was independent of bacterial strain but dependent on temperature; nodules were fewest in the lowest and most in the highest temperature regime. Plant yield was determined by interactions between temperature and strain and was generally greatest at whole plant temperatures of 25/20°C.When nodulated plants growing at 25°C were transferred to a range of root temperatures, plants grew best at 20° and 25°C and with strains CB782 and CB2116.

Effect of the Osmotic Environment on the Balance between Uptake and Release of Sucrose and Amino Acids by the Seed Coat and Cotyledons of Developing Seeds ofPisum sativum

Effect of the Osmotic Environment on the Balance between Uptake and Release of Sucrose and Amino Acids by the Seed Coat and Cotyledons of Developing Seeds of<i>Pisum sativum</i>

Effect of Water Stress on Canopy Senescence and Carbon Exchange Rates in Cotton1

The work reported here was done as part of an effort to develop a physiological process level data base for the simulation of cotton (Gossypium hirsutum L.) growth and yield. The effects of water stress on vegetative growth and on carbon exchange rate (CER) in cotton canopies were investigated in naturally illuminated, controlled environment cabinets (SPAR units). The control treatment was irrigated daily. In the other treatments, irrigation was stopped just before the appearance of the first blooms. An extra low water treatment was allowed to dry much faster than the low water treatment. Water stress had a strong effect on vegetative growth. Rate of increase in plant height and leaf area declined when midday leaf water potential was lower than −1.4 MPa, and they were almost zero at −2.0 to −2.5 MPa. Water stress had a similar effect on the CER over a wide range of radiation intensities. CER started to decline &lt; 2 weeks after irrigation was stopped, and it was about 50% of the control when midday leaf water potential reached −2.0 to −2.5 MPa. Two different mechanisms are suggested for the effect of water stress on canopy photosynthesis. A direct effect on single leaves may have closed stomata, increased mesophyll resistance, or decreased Hill reaction activity. Additionally, there was the long‐term effect of reduced leaf growth, which produced a canopy consisting mainly of old, less photosynthetically efficient leaves.

Modifications to A Controlled Environment Cabinet to Gain Proportional Control Over Temperature and Humidity

Modifications to A Controlled Environment Cabinet to Gain Proportional Control Over Temperature and Humidity

Relationships between root permeability to water, leaf conductance and transpiration rate in sunflower (Helianthus annuus L.) cultivars

The relations between leaf conductance (gl) transpiration rate and root permeability to water (Rp) of three sunflower (Helianthus annuus L.) cultivars grown in a controlled environment cabinet are described. No differences in transpiration rates were found but it was shown that plants with low values of Rp have active stomatal closure with favourable consequences for water use efficiency under water limiting conditions. Rp was estimated by applying hydrostatic pressure on the root system. Values of Rp per unit root volume ranged from 0.34×10−5 to 16.75×10−5 (s MPa−1). There were significant inter-cultivar differences (P<0.05) in Rp and gl and an inverse correlation between Rp and the maximum values cf gl within cultivars. Pressure applied on the root system is proposed as a useful tool for the determination of differences in the root permeability to water amongst sunflower cultivars.

The basis of variation in date of ear emergence under field conditions among the progeny of a cross between two winter wheat varieties

SummaryFrom the progeny of a cross between the winter wheat varieties Norman and Talent early and lateF5lines were selected in the field. These selections and the two parental varieties were grown in controlled environment cabinets to assess their sensitivity to photoperiod and vernalization.TheF5selections and Norman and Talent were also grown in field trials, at the Plant Breeding Institute in Trumpington, and at The Murrays Experimental Farm of the Scottish Crop Research Institute, near Edinburgh.Norman was more sensitive to photoperiod and vernalization than Talent. The earlyF5lines were relatively insensitive to photoperiod and/or vernalization. The late lines were sensitive to both photoperiod and vernalization. Differences in date of ear emergence among the selections were found which were independent of photoperiod and vernalization sensitivity. This variation in ear emergence, described as earlinessper se, was similar under controlled environment conditions and in the field, and was also shown to be similar in magnitude to that due to differences in sensitivity to photoperiod and vernalization. Both sources of variation can be exploited to modify time of ear emergence under field conditions in Great Britain.

Nitrate Effect on Nodulation of Soybean by Bradyrhizobium japonicum1

It is not known whether NO−3 inhibition of nodulation is primarily due to effects on the host plant or on the bacterials train. This study was conducted to evaluate the effect of NO−3 on nodule appearance and development of nitrogenase (acetylene reduction) activity of various Glycine max (L.) Merr. cultivar ✕ Bradyrhizobiumja ponicum (Kirchner) Buchanan strain combinations. Plants were grown hydroponically in controlled environment cabinets. NO−3 was either resupplied daily (“maintained”) during the growth period or allowed to deplete with plant growth (“rundown”). Nodule development was delayed all NO−3 treatment conditions (both maintained and rundown), the delay being more severe at higher NO−3 concentrations. The external concentration of NO−3 rather than the rate of NO−3 uptake appeared to have a major effect on the initial stages of nodulation. Treatment conditions providing similar rates of NO−3 up take from different solution NO−3 concentrations( 4.0 mM rundown vs. 0.5. mM maintained) resulted in a more marked inhibition of nodule appearance at the higher level of solution NO−3. Maintaining the solution concentration of NO−3 at 1.0 mM following the appearance of nodules greatly retarded, or prevented, the development of nitrogenase activity (C2H2 reduction). Minor differences in the tolerance of nodulation to NO−3 were observed among eight B. j. uponicum strains (preselected from 46 strains). More variation existed among 12 soybean cultivars (preselected from 23 cultivars) with respect to their ability to nodulate in the presence of NO−3. The cvs. Elf and Avoyelles were notable in having good nodulation tolerance to NO−3 when infected by USDA110. This indicated that, with selection and breeding, enhanced NO−3 tolerance of nodulation between soybean and B. japonicum should be possible.

Chlorine deficiency in red clover grown in solution culture

Abstract Symptoms of chlorine deficiency occurred in red clover (Trifolium pratense, L.) grown, in solution culture, in a controlled environment cabinet with its air intake filtered through activated carbon. The first visible symptom was a curling of the leaflets on the youngest leaves. Within a few days, some newly expanded leaflets shrivelled completely, and older leaflets developed a brown necrosis which started at the tip and extended backwards particularly at the margins. Subsequently there was a general stunting of growth and the collapse of some petioles. The results of analysis of deficient plants indicated that the critical concentration of chlorine in the leaf + petiole of red clover was at least 200 μg g‐1 dry weight.

DICHOTOMOUS BRANCHING IN LATERAL ROOTS OF PINE: THE EFFECT OF 2‐CHLOROETHYLPHOSPHONIC ACID ON SEEDLINGS OF PINUS RADIATA D. DON

SummarySeedlings of Pinus Radiata D. Don were grown in sand in a glasshouse and in nutrient solution in a controlled environment cabinet and treated with 2‐chloroethylphosphonic acid (CEPA) applied in solution to whole root systems. A wide range of concentrations of CEPA (0.1 to 120 mg 1−1) promoted dichotomous branching of secondary and tertiary roots, on most seedlings, whether growing in solution or in sand.There was considerable variation in the response of individual plants to CEPA, with some treated plants branching profusely and some scarcely or not at all. Absence of artificial aeration of the solution in which root systems were growing enhanced the effect of CEPA in promoting root forking.

The effect of temperature on the activity and metabolism of glyphosate applied to rhizome fragments of elymus repens (=Agropyron repens)

AbstractThe effect of temperature on the activity and metabolism of glyphosate, as its mono(isopropylammonium) salt, in single‐node rhizome fragments of Elymus repens was investigated in controlled environment cabinets. Post‐treatment temperatures of 26/16° (day/night) reduced the activity of the herbicide compared with that at 10/6°, respectively. Under both temperature regimes and using [14C]glyphosatemono(isopropylammonium), more [14C]glyphosate accumulated in the node tissues and buds than in the internodes, but at teh higher temperature the rate of glyphosate metabolism was greater, and more 14C was lost as [14C]carbon dioxide. Evidence is presented to indicate that plant extracts contained at least two components which yielded glyphosate and aminomethylphosphonic acid after both acid or base treatment, but not on incubation with β‐glucosidase. It is therefore tentatively suggested that these metabolites are not β‐glycosides but perhaps are conjugates with other natural plant constituents involving the phosphonyl and/or amino groups of the herbicide.

Nodulation studies on legumes exotic to Australia: Hedysarum coronarium

Symbiotic experiments in glasshouse, controlled environment cabinet, and field were conducted with four lines of sulla (Hedysarum coronarium) and 15 strains of Rhizobium spp. This plant is highly Rhizobium-specific and appropriate strains are most unlikely to occur naturally in Australia. Under several sets of experimental conditions, H. coronarium nodulated abundantly and effectively with homologous rhizobia introduced from Spain and Italy. The optimum temperature for nitrogen fixation was relatively low (approx. 21°C) but significant interactions between line of host, strain of rhizobia, and growth temperature were frequent. The rhizobia were persistent in soil.

Nodulation studies on legumes exotic to Australia:Hedysarum coronarium

Symbiotic experiments in glasshouse, controlled environment cabinet, and field were conducted with four lines of sulla (Hedysarum coronarium) and 15 strains of Rhizobium spp. This plant is highly Rhizobium-specific and appropriate strains are most unlikely to occur naturally in Australia. Under several sets of experimental conditions, H. coronarium nodulated abundantly and effectively with homologous rhizobia introduced from Spain and Italy. The optimum temperature for nitrogen fixation was relatively low (approx. 21°C) but significant interactions between line of host, strain of rhizobia, and growth temperature were frequent. The rhizobia were persistent in soil.

Effects of temperature on the flowering and seed production of Stylosanthes guianensis cultivars

SUMMARYSeedlings of Stylosanthes guianensis var. guianensis were grown for 75 days in 16 h photoperiods and transferred to controlled environment cabinets for a further 112 cycles set at 12 h days and 18, 21, 24 or 27 OC constant temperatures. Floral initiation (FI) occurred in cv. Cook after 21 short‐day cycles of 12 h and was independent of temperature. Warm temperatures delayed FI in cv. Schofield and hastened it in cv. Endeavour. Rate of node appearance was positively and the duration of the phase FI to flower appearance negatively related to temperature. Spike production and floret number per spike were maximal for Cook and Endeavour at 24°C; seed setting was independent of temperature above 18°C in Cook. Growth, flowering, and seed production of Endeavour required warm temperatures, but Cook was more versatile in its adaptation to varying temperature regimens.

Variation in the low temperature growth and frost tolerance of natural genotypes of Trifolium repens L. from Britain and Norway

SummarySixty-two genotypes of Trifolium repens (white clover) collected from latitudes 52° to 68° N and five selected genotypes of the cultivar S.184 were screened for shoot growth at low temperature and short daylengths in a controlled environment cabinet and in the field, and subjected to cold hardiness treatments ranging from – 2·5 to – 14·0 °C.Considerable variation was discovered in several of the growth characteristics and in the frost tolerance of the genotypes. Genotypes exhibiting the highest rates of stolon extension were found in the more southerly latitudes. A high proportion of leaves produced during winter on the primary stolons of the selected cultivar plants subsequently died during the late spring at the upland field site, but several of the naturally occurring genotypes were able to retain more leaves per stolon in spring. Some genotypes appeared to maintain either short or long internodes throughout the spring in the field, whilst others produced relatively short internodes in early spring and long internodes later in the season, and vice versa. Only a small percentage of the genotypes possessed relatively long leaflets. A correlation was found between maximum leaflet length of the genotypes in early spring, and maximum leaflet length in late spring.No relationship was found between frost tolerance and the growth of plants at low temperature. Frost sensitive and tolerant genotypes were found throughout the latitudinal and altitudinal ranges studied. Exposure to prevailing winds and possibly snow cover at the site of origin appeared to be important factors associated with the frost tolerance of T. repens plants.

Influence of environmental factors on the development of the anthracnose diseases of Stylosanthes spp

The influence of temperature, period of leaf wetness after inoculation, and relative humidity on the development of the type A and type B diseases of Stylosanthes spp. caused by Colletotrichum gloeosporioides was studied in controlled environment cabinets. Severe disease of both types developed in plants incubated at temperatures of 20-30�C, and given 24 h of leaf wetness after inoculation. Provided these conditions were imposed, high levels of disease developed following the leaf wetness period, irrespective of the relative humidity (40-50% or &gt;95%). High levels of disease developed for both the type A and type B combinations at temperatures in the range 20-3OoC, but only the type A disease developed at &gt;34�C. Neither disease developed at constant temperatures of 15 or 37�C. The use of these results in the development of a model to predict field infection is discussed.

Cultural Studies of Protoplasts and Leaf Callus of Trigonella corniculata and T. foenum-graecum

Summary Mesophyll protoplasts were isolated using a Biogel-purified enzyme mixture from leaflets of vegetative and flowering stems of Trigonella corniculata and T. foenum-graecum grown in a controlled environment cabinet. Protoplasts of both species divided in liquid medium with a plating efficiency of 70%. Cell suspensions initiated from leaf callus of T. corniculata yielded protoplasts which formed callus. In contrast, protoplasts were not obtained from cell suspensions of T. foenum-graecum . Callus derived from leaf explants, mesophyll protoplasts and cell suspension protoplasts of T. corniculata formed embryoids and shoots, but tissues of T. foenum-graecum were recalcitrant to regeneration. These results, including the difficulties associated with T. foenum-graecum , are discussed in relation to recent progress on regeneration in forage legumes.