Controlled-environment Glasshouses Research Articles

Effects of Atmospheric CO2 Enrichment and Root Restriction on Photosynthesis and Dry Matter Partitioning in Tropical Fruit Crops

Banana (Musa sp.), mango (Mangifera indica), and avocado (Persea americana) plants were grown in controlled-environment glasshouses in ambient (350 μmol CO2/mol) and enriched (700–1000 (mol CO2/mol) atmospheric CO2 concentrations. At each CO2 concentration, plants were either exposed to sink-limiting (root restriction) or non-sink-limiting conditions (no root restriction). Total carbon assimilation and dry matter accumulation were generally greater for plants in the enriched CO2 environment than for plants grown in ambient CO2. However, plants grown in the enriched CO2 environment were less efficient at assimilating carbon than plants grown in ambient CO2. There was a downward regulation of net CO2 assimilation due to root restriction that resulted in less dry matter accumulation than in non-root-restricted plants. This may explain the lower net CO2 assimilation rates often observed for tropical fruit trees grown in containers compared to those of field-grown trees. Atmospheric CO2 enrichment generally did not compensate for reductions in net CO2 assimilation and dry matter accumulation that resulted from root restriction.

Effects of Photoperiod, Temperature and Asynchrony between Thermoperiod and Photoperiod on Development to Panicle Initiation in Sorghum

Abstract The duration of the vegetative phase (i.e. days from sowing to panicle initiation) in sorghum [Sorghum bicolor(L.) Moench] is affected by photoperiod and temperature. Plants of several contrasting genotypes of sorghum were grown in controlled-environment growth cabinets with either synchronous or asynchronous photoperiods and thermoperiods. Apical development was recorded. Diurnal asynchrony between photoperiod and thermoperiod reduced durations to panicle initiation when the temperature warmed after lights went on and cooled after lights went off, but increased these durations when the temperature warmed before lights went on and cooled before lights went off. These effects were shown in the maturity lines 60M and SM100 and also in the USA cv. RS610 and the Sudanese landrace IS22365, but their magnitude varied with genotype, photothermal regime, and the degree of asynchrony. The greatest effect was detected in IS22365 grown at 30/21 °C (12 h/12 h) with a 12 h d−1photoperiod when the temperature warmed 2.5 h before lights went on and cooled 2.5 h before lights went off, when the duration from sowing to panicle initiation was 69 d compared with 37 d in the control (synchronous photoperiod and thermoperiod in each diurnal cycle). Reciprocal transfers of plants of IS22365 between short and long days revealed that asynchrony principally affected the duration of the photoperiod-insensitive pre-inductive phase of development; i.e. asynchrony affected the time (age) at which the plants were first able to respond to photoperiod. In that investigation in controlled-environment growth chambers, the subsequent photoperiod-sensitive inductive phase continued until panicle initiation. Subsequent reciprocal transfer experiments in controlled-environment glasshouses in four different alternating temperature regimes employed synchronous photoperiods and thermoperiods in short (11 h) days with temperature warming 1.5 h after the beginning of the day in long (12.5 h) days. In those investigations, photoperiod sensitivity ended some time before (2.5–8.1 d, mean 5.7 d) panicle initiation in IS22365, Naga White and Seredo. Moreover, whereas the duration of the photoperiod-insensitive pre-inductive phase was affected by temperature, the durations of the photoperiod-sensitive inductive and the photoperiod-insensitive post-inductive phases were not.

Leaf Appearance in Cowpea: Effects of Temperature and Photoperiod

Leaf appearance in crop plants is an important process involved in canopy development. The environmental control of leaf appearance has not been studied in cowpea [Vigna unguiculata (L.) Walp.]. This study was conducted to determine whether photoperiod has any effect on the rate of leaf appearance (RLA) and to determine the phyllochron and its base temperature in cowpea. Five genotypes from W. Africa were sown on nine occasions between 1990 and 1992 at Kano, Nigeria, (12°03′N). Plants were grown in pots under short (9.7–10.8 h d−1), natural (12.3–13.5 h d−1), and long (13.5–14.4 h d−1) day lengths and at mean daily temperatures of between 20.9 and 29.8°C. Eight genotypes, including the five genotypes grown in Nigeria, were also grown at seven mean temperatures ranging from 15.4 to 33.7°C in controlled environment glasshouses during 1994 in the UK. Leaf number on the main shoot was recorded every 2 to 3 d during the course of the experiments. No significant effects (P > 0.05) of photoperiod on RLA were detected in any genotype. Temperature significantly (P < 0.001) affected RLA in all genotypes. The relationship between RLA and mean temperature was similar in experiments in Nigeria and controlled environments. A comparison of the combined Nigerianand controlled environment data sets revealed significant (P < 0.01) differences between genotypes in the intercept but not in the slope of the relationship between RLA and mean temperature. The phyliochron, expressed as thermal time (0) per leaf, was therefore the same in all genotypes, 42°C d, above a base temperature that varied from 7 to 12°C. These values of the phyllochron and its base temperature are similar to those reported for other tropical legumes.

Effects of soil moisture deficits on the water relations of bambara groundnut (Vigna subterraneaL. Verdc.)

The components of leaf water potential (Ψ I ) and relative water content (RWC) were measured for stands of bambara groundnut (Vigna subterranea) exposed to three soil moisture regimes in controlled-environment glasshouses at the Tropical Crops Research Unit, Sutton Bonington Campus. Treatments ranged from fully irrigated (wet) to no irrigation from 35 days after sowing (DAS) (dry). RWC values varied between 92-96% for the wet treatment, but declined from 93% to 83% in the dry treatment as the season progressed. Ψ I at midday decreased in both the wet and dry treatments, but the seasonal decline was more pronounced in the latter: seasonal minimum values were -1.19 and - 2.08 MPa, respectively. Plants in the wet treatment maintained turgor (Ψ p ) at about 0.5 MPa throughout the season, whereas values in the dry treatment approached zero towards the end of the season. There was a linear relationship between Ψ p and Ψ I , with Ψ p approaching zero at a Ψ I of -2.0 MPa. Mean daily leaf conductance was consistently higher in the wet treatment (0.46-0.79 cm s -1 ) than in the intermediate and dry treatments (0.13-0.48 cm s -1 ). Conductances in the intermediate and dry treatments were similar, and the lower evapotranspirational water losses in the latter were attributable to its consistently lower leaf area indices (L): L at final harvest was 3.3, 3.3 and 1.9 for the wet, intermediate and dry treatments. Bambara groundnut was apparently able to maintain turgor through a combination of osmotic adjustment, reductions in leaf area index and effective stomatal regulation of water loss.

Effects of atmospheric CO2 enrichment and root restriction on leaf gas exchange and growth of banana (Musa)

The effects of atmospheric CO2 enrichment and root restriction on photosynthetic characteristics and growth of banana (Musa sp. AAA cv. Gros Michel) plants were investigated. Plants were grown aeroponically in root chambers in controlled environment glasshouse rooms at CO2 concentrations of 350 or 1 000 μmol CO2 mol‐1. At each CO2 concentration, plants were grown in large (2001) root chambers that did not restrict root growth or in small (20 1) root chambers that restricted root growth. Plants grown at 350 μmol CO2 mol‐1 generally had a higher carboxylation efficiency than plants grown at 1 000 μmol CO2 mol‐1 although actual net CO2 assimilation (A) was higher at the higher ambient CO2 concentration due to increased intercellular CO2 concentrations (Ci resulting from CO2 enrichment. Thus, plants grown at 1 000 μmol CO2 mol‐1 accumulated more leaf area and dry weight than plants grown at 350 μmol CO2 mol‐1. Plants grown in the large root chambers were more photosynthetically efficient than plants grown in the small root chambers. At 350 μmol CO2 mol‐1, leaf area and dry weights of plant organs were generally greater for plants in the large root chambers compared to those in the small root chambers. Atmospheric CO2 enrichment may have compensated for the effects of root restriction on plant growth since at 1 000 μmol CO2 mol‐1 there was generally no effect of root chamber size on plant dry weight.

Growth, development and yield of bambara groundnut (Vigna subterranea) in response to soil moisture

SUMMARYStands of bambara groundnut (Vigna subterranea (L.) Verde.) were grown in five controlledenvironment glasshouses at the Tropical Crops Research Unit, University of Nottingham, Sutton Bonington Campus, in 1990. Five soil moisture regimes were imposed (one per house), from fully irrigated each week (treatment A), to no irrigation after crop establishment at 35 days after sowing (DAS) (treatment E). Decreasing the amount of water applied resulted in a decline in total dry matter production and harvest index, and a reduction in pod yield from 412 (treatment B) to 0·041 ha-1 (treatment E) at 125 DAS. A maximum leaf area index of 5–4 was achieved by treatments B and C at 90 DAS, resulting in a fractional interception of c. 0·8 of incoming radiation. Total accumulated radiation interception values were 749, 693, 688, 618 and 554 MJ m-2 for treatments A, B, C, D and E, respectively. The efficiency of conversion of the radiation intercepted into dry matter was reduced from 1·41 to 0·50 g MJ-1 by drought.

Assessment of soybean seed vigour tests for eastern Australia

Vigour testing was undertaken on seed from 4 soybean [Glycine max (L.) Merr.] cultivars taken from field trials in eastern Australia. The seed from each cultivar exhibited moderate to good germination and a range in vigour. Vigour tests consisted of the controlled deterioration and modified versions of the accelerated aging test. Accelerated aging was carried out in 4 ways using 2 periods of incubation (76 and 96 h), with or without the seed protectant Thiram to control saprophytic fungi. Results were compared with seedling emergence from the same seed samples when planted in a controlled environment glasshouse. A combination of 2 day/night temperatures, cold (18/13�C), warm (33/28�C), and 3 soil moisture regimes, dry (-0.3 MPa), field capacity (-0.01 MPa) and saturated soil, produced a total of 6 different environments. Emergence was also recorded under a moderate daylnight temperature of 23/18�C in soil at field capacity. The standard germination test and modified accelerated aging test with a 72-h incubation period with Thiram were significantly (P<0.01) correlated with emergence from all 7 soil environments. A 96-h period of accelerated aging (with or without Thiram) tended to suppress germination and there was no correlation with emergence from most soil environments. The controlled deterioration test correlated with seedling emergence from most soil environments except for dry soil. The vigour test which gave the best indicator of performance under a range of different seedbed moisture and temperature conditions was the modified accelerated aging test using a 72-h incubation period with Thiram.

The effects of elevated carbon dioxide, temperature and soil moisture on the water use of stands of groundnut (Arachis hypogaeaL.)

Stands of groundnut (Arachis hypogaea L. cv. Kadiri 3) were grown in controlled environment glasshouses at two mean air temperatures (28° C and 32° C), two atmospheric CO 2 concentrations (371 ppmv and 700 ppmv) and two soil moisture treatments (irrigated weekly to field capacity or allowed to dry from 22 d after sowing). The transpiration equivalent, Ω w (g kPa kg −1 ) - the product of the accumulated biomass/transpired water ratio and the saturation deficit - was calculated for all the treatments using above-ground harvest, root core and neutron probe measurements. Neither temperature nor soil moisture treatment was found to have an effect on Ω w

The Effects of Elevated Atmospheric Carbon Dioxide and Water Stress on Ligth Interception, Dry Matter Production and Yield in Stands of Groundnut (Arachis hypogaeaL.

Stands of groundnut (Arachis hypogaea L.), a C3 legume, were grown in controlled-environment glasshouses at 28 °C (±5°C) under two levels of atmospheric CO2 (350 ppmv or 700 ppmv) and two levels of soil moisture (irrigated weekly or no water from 35 d after sowing). Elevated CO2 increased the maximum rate of net photosynthesis by up to 40%, with an increase in conversion coefficient for intercepted radiation of 30% (from 1–66 to 2–16 g MJ−1) in well-irrigated conditions, and 94% (from 0–64 to 1·24 g MJ−1) on a drying soil profile. In plants well supplied with water, elevated CO2 increased dry matter accumulation by 16% (from 13·79 to 16·03 t −1 ) and pod yield by 25% (from 2·7 to 3·4t ha−1). However, the harvest index (total poddry weight/above-ground dry weight) was unaffected by CO2 treatment. The beneficial effects of elevated CO2 were enhanced under severe water stress, dry matter production increased by 112% (from 4·13 to 8·87 t ha−1) and a pod yield of 1·34t ha−1 was obtained in elevated CO2, whereas comparable plotsat 350 ppmv CO2 only yielded 0·22 t ha-1. There was a corresponding decrease in harvest index from 0·15 to 0·05. Following the withholding of irrigation, plants growing on a stored soil water profile in elevated CO2 could maintain significantly less negative leaf water potentials (P<0·01) for the remainder of the season than comparable plants grown in ambient CO2, allowing prolonged plant activity during drought. In plants which were well supplied with water, allocation of dry matter between leaves, stems, roots, and pods was similar in both CO2 treatments. On a drying soil profile, allocation in plants grown in 350 ppmv CO2 changed in favour of root development far earlier in the season than plants grown at 700 ppmv CO2, indicating that severe waterstress was reached earlier at 350 ppmv CO2. The primary effects of elevated CO2 on growth and yield of groundnut stands weremediated by an increase in the conversion coefficient for intercepted radiation and the prolonged maintenance of higher leaf water potentials during increasing drought stress.

Effect of Temperature on Interception and Conversion of Solar Radiation by Stands of Groundnut

Stands of groundnut were grown in controlled environment glasshouses at air temperatures of 19, 22, 25, 28, and 31 °C. Leaf area index (L) increased with rise of temperature, and after 85 d was about 10-fold larger at 31 °C than 19 °C. Over most of the range of temperature, both L and fractional interception of solar radiation (/) were functions of thermal time accumulated from sowing (above a base of 10 °C). In this respect, they were tightly coupled to developmental rate at the main apex. In one experiment, only 38% of seeds emerged at 22 °C and 21% at 19 °C, compared with more than 70% at 25 °C and 31 °C, but the low population density was compensated by faster leaf expansion by each plant (at 22 °C only) and a greater fraction of solar radiation intercepted by unit leaf area. The amount of solar radiation intercepted by stands increased with rise in temperature, but the greatest differences between treatments occurred before the canopies achieved complete ground cover (i.e./> 0-9) and the relative effect of a rise in temperature diminished the longer the duration of growth. The dry matter produced for unit solar radiation intercepted was not strongly affected by temperature between 22 °C and 31 °C, where the mean was 21 g MJ1; the value at 19 °C was uncertain since the stands were sparse throughout the experiment. After 85 d, the stand at 31 °C had produced eight times the dry matter of that at 19 °C—a difference caused mainly by the effect of temperature on the rates of development and expansion.

Response to Temperature in a Stand of Pearl Millet

Effects of temperature on the size of the leaf canopy, the stems and the panicles were investigated for stands of pearl millet in controlled-environment glasshouses. Expansion of each structure was examined in terms of a duration and a mean rate. The duration (t) for vegetative structures responded to temperature as a normal developmental period, in that l/t increased linearly with rise in temperature between a base (10 °C) and an optimum (30 to 35 °C). The rate for these structures also increased linearly with temperature between a similar base and optimum. Effects of temperature on rate compensated for those on duration, such that the leaf area index and height of the canopy were little affected by temperature. The panicles responded slightly differently in that length increased with rise in temperature by about 2% per degree. For all structures, rate, duration and size were little influenced by unsystematic differences between treatments in the rate of dry matter production.

Temperature and irradiance effects on yield in Cowpea ( Vigna unguiculata)

Cowpea ( Vigna unguiculata (L.) seed yield is very sensitive to environment despite the reputation the species has for hardiness. The responses of the variety TVu4552 to differing temperatures after flowering and to irradiance were examined in controlled environment glasshouses. Seasonal variation in irradiance was positively correlated with pod number, while seed number per pod and mean seed weight remained constant. Carbon dioxide assimilation rate (ifA) of recently expanded leaves of plants grown at 21 16 °C day/night temperature regime was half that of plants grown at 27 22 ° C and 33 28 ° C , although leaves of plants grown at these warmer regimes had instantaneous A's that were unchanged in the range 20–28°C. Grain yield was influenced by the temperature after flowering in two ways: with high temperature there was a decrease in pod number; with temperatures below 21°C there was a decrease in seed number and size. Associated with decrease in pod number at high temperatures there was earlier leaf senescence. Although early senescence would limit assimilate supply and pod development at high temperatures, at a constant intermediate temperature ( 27 22 ° C ) there was no seasonal variation in the timing of senescence despite a doubling of radiation from winter to summer. The failure to set seed at low temperatures was a response localized within the flower and the developing pod. Histochemical staining of isolated pollen and of the stigma indicated that at low temperature (18°C) pollen was viable and that pollination occurred. Early embryo development was apparently restricted at low temperature and this response was evident over a period of up to 5 days after pollination.

Saturation Deficit, Canopy Formation and Function inSorghum bicolor(L.)

Hamdi, Q. A., Harris, D. and Clark, J. A. 1987. Saturation deficit, canopy formation and function in Sorghum bicolor (L.).—J. exp. Bot. 38: 1272-1283. Stands of two sorghum genotypes, SPV 354 and MK 35-1, were grown in controlled-environment glasshouses at three levels of saturation vapour pressure deficit (SD), at the same temperature and with unrestricted soil moisture. Vegetative growth was monitored by growth analysis and non-destructive measurements were made of leaf appearance, leaf extension and final size, and fractional light interception. Rates of leaf appearance were reduced at high SD in both genotypes, although this may have been an artefact of the method of measurement, and MK 35-1 produced leaves more slowly than SPV 354. Leaf extension was also slowed as SD increased and, since the duration of extension for individual leaves of a given age remained constant, resulted in smaller leaf area indices (L) in dry air than in humid air. The cumulative interception of radiation and the dry matter/radiation quotient (e) both decreased as SD increased.

Effects of temperature during latter stages of nut development on growth and quality of macadamia nuts

Macadamia ( Macadamia integrifolia Maiden and Betche) trees were subjected to day temperatures of 15, 25, 30 or 35°C in controlled-environment glasshouses after rapid expansion of nuts had largely been completed and oil accumulation commenced. Nut growth was higher at 25–30°C, and kernel growth was reflected in higher kernel recovery. Oil accumulation was most rapid at 25°C; all kernels containing 72% or more oil (first-grade kernels) at later harvests. Kernel growth, recovery and oil content were low at 15 and 35°C. At high temperature, kernel weight and hence kernel recovery actually declined, indicating a net loss of assimilate. Most kernels at 35°C were inferior, containing less than 72% oil. Thus, extreme temperatures during later stages of nut development adversely affect nut growth and oil accumulation and result in poor kernel quality.

Development and Growth of Pearl Millet (Pennisetum typhoides) in Response to Water Supply and Demand

SUMMARYStands of pearl millet were grown in three controlled environment glasshouses in which were imposed different combinations of atmospheric saturation deficit (1.5 to 2.3 kPa) and soil water content (fully irrigated and not irrigated). Consistent differences in saturation deficit (SD) were maintained throughout the experiment (100 days) but a high water table restricted differences in water supply to the first 40 days. Responses to SD and soil water were observed in some variables but not in others. Developmental processes such as the rate of leaf appearance were unaffected, whereas the efficiency for conversion of intercepted solar energy decreased by 24% and the rate at which the canopy expanded by 50%, in the driest compared to the wettest conditions.

Influence of Saturation Deficit on Leaf Production and Expafision in Stands of Groundnut-{&lt;italic&gt;Arachis hypogaea&lt;/italic&gt; L.) Grown Without Irrigation

The response of leaf area expansion to atmospheric saturation deficit (SD) and soil moisture deficit was examined in terms of leaf water potential (ψ1) and turgor potential (ψp), as part of a wider study of the effects of SD on groundnut growth. Stands of plants were grown at four levels of SD and without irrigation in controlled environment glasshouses. A fifth stand was grown at low SD on soil kept irrigated to field capacity. Large saturation deficits accelerated the depletion of soil moisture reserves in the unirrigated stands and greatly reduced leaf area index, particularly in the driest treatment. Leaf number per plant and leaf size both decreased as SD increased, but the effect on leaf size was greater than on number. SD had less effect than soil water deficit on leaf production. Turgor potential and leaf extension rate (R) were both reduced at high saturation deficits and R was linearly related to ψp between 0900 and 1600 h. However, leaf extension rate and turgor potential were poorly correlated between 0400 and 0700 h in the driest treatment.

EFFECTS OF SOIL MOISTURE STRESS ON THE WATER RELATIONS AND WATER USE OF GROUNDNUT STANDS

SummaryThe work described here formed part of a detailed study of the effects of temperature and water stress on growth and development in groundnut (Arachis hypogaea L.). Stands of plants were grown in controlled environment glasshouses at mean air temperatures of 25, 28 and 31 °C. Half of each stand was irrigated whenever soil water potential at 10 cm reached –20 kPa. The other half received no further irrigation after sowing, when the soil profile was at field capacity. The effects on plant water status, stomatal conductance and water use were investigated regularly during the growing season.Leaf water potential (Ψ1), turgor potential (Ψp) and stomatal conductance (g1) were already reduced in unirrigated plants by 29 d after sowing (DAS), when leaf area index (LAI) was still below 0.5; g1 was more strongly affected than water status. These differences persisted throughout the season as stress increased, g1 was poorly correlated with Ψ1 and Ψp and of ten exceeded 2 cm s−1 in wilted leaves. LAI was not affected before 40 to 45 DAS but was reduced by 20 to 25 % in unirrigated plants between 60 DAS and final harvest. The decreases in g1 and LAI reduced canopy conductance by up to 40 %. The conservative influence of decreased g1 in unirrigated plants was negated by increases in leaf‐to‐air vapour pressure difference caused by their higher leaf temperatures. Transpiration rates were therefore similar in both treatments and the lower total water use of the unirrigated stand resulted entirely from its smaller LAI. Unirrigated plants made less vegetative growth but produced more pegs and pods. However, impaired pod‐filling reduced pod yields by around 35 %.

The Influence of Temperature and Water Deficits on the Partitioning of Dry Matter in Groundnut (Arachis hypogaea L.)

The partitioning of dry matter to stems, leaves and pods of groundnut was examined as a function of mean air temperature and water stress. Different levels of stress were imposed by growing plants on stored moisture at five different mean temperatures between 19 °C and 31 °C and at four levels of saturation vapour pressure deficit. Stands of plants were grown in controlled environment glasshouses. The ratio of pod to shoot weight (PWR) was greatest at 22 °C and decreased from 0.28 to 0.04 as temperature increased to 31 °C. PWR was closely related to the number of pods longer than 5.0 mm but negatively correlated with stem weight ratio. In general, water stress had a minor influence on PWR although peg and pod production were stimulated in five of the nine treatments. Mild water stress promoted peg and pod production because reproductive growth was less affected than the growth of leaves and stems, the major sinks early in the reproductive phase. In one treatment, mild water stress increased PWR by a factor of 2.2 indicating that when adequate water is supplied to relieve a mild stress, PWR can be greatly increased

Effects of Atmospheric Saturation Deficit on the Stomatal Conductance of Pearl Millet (Pennisetum typhoidesS. and H.) and Groundnut (Arachis hypogaeaL.)

Experiments were carried out to investigate the influence of atmospheric saturation deficit on the stomatal conductances of millet and groundnut plants grown in undisturbed soil in controlled environment glasshouses. Environmental conditions during growth were maintained close to those experienced in the semi-arid tropics. The results demonstrated that the stomatal conductances of well-watered plants of both species were affected strongly by changes in saturation deficit. The response was stronger at higher irradiances when variations in saturation deficit between 1.5 and 3.0 kPa caused 3–4-fold changes in leaf conductance. However, the stomatal response was greatly reduced or absent in unirrigated plants in which stomatal conductances were reduced. Reduction of the transpiring leaf area by covering some of the leaves increased the leaf conductances of the remaining leaves and partially restored the stomatal response to saturation deficit in unirrigated plants. Leaf conductance was sensitive to the transpiring area per plant and declined as the transpiring area increased. However, the reduction in mean leaf conductance was insufficient to prevent an increase in canopy conductance owing to the increased transpiring area: The results are compared to earlier field data for millet, and the possible origin of the stomatal response is discussed.

Carbon dioxide assimilation measurement in a controlled environment glasshouse

Carbon dioxide assimilation measurement in a controlled environment glasshouse