Soybean Seed Growth in Response to Long-Term Exposures to Differing Oxygen Partial Pressures

Sinclair, Thomas R.; Ward, J.; Randall, Carolyn A.

doi:10.1104/pp.83.3.467

Cited by 18 publications

(14 citation statements)

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“…Quebedeaux and Hardy (12) described complete inhibition of seed set during growth at 5% 02-Subsequent experiments were conducted to explain these observations by measuring inhibition of respiration by developing seeds (5) or of phloem unloading from the seed coat (16) in short term experiments under very low 02 tensions. These explanations imply that it is the local 02 environment around the developing pod which influences seed set; however, when Sinclair et al (15) exposed developing soybean pods to 10% 02, they found only a 20% decrease in seed dry weight, compared to 81% observed by Quebedeaux and Hardy (13) when the whole aerial portion of the plant was exposed to the same regimen. These results argue that seed set is indirectly influenced by subambient 02 effects on the vegetative portion of the plant in addition to any direct inhibition of respiration and phloem unloading which may occur in the pod.…”

Section: Discussionmentioning

confidence: 91%

Response of Two Wheat Cultivars to CO₂ Enrichment under Subambient Oxygen Conditions

Musgrave¹,

Strain²

1988

Plant Physiol.

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Two cultivars of wheat (Triticum aestivum L. cvs Sonoita and Yecora Rojo) were grown to maturity in a growth chamber within four subchambers under two CO2 levels (350 or 1000 microliters per liter) at either ambient (21%) or low 02 (5%). Growth analysis was used to characterize changes in plant carbon budgets imposed by the gas regimes. Large increases in leaf areas were seen in the low 02 treatments, due primarily to a stimulation of tillering. Roots MATERIALS AND METHODSAll experiments were conducted in a controlled environment chamber in the Duke University Phytotron. The chamber operated on a 14-h photoperiod and maintained the interior of four Plexiglas subchambers at 26/20°C day/night 14-h thermoperiod and light levels at 400 ,umol m-2 sec -PAR. The subchambers (30 cm wide x 80 cm long x 90 cm high), equipped with fans and watering ports as described by White (17), were used to maintain separate gas treatments with flowthrough rates of 1 L min-1 (Fig. 1).Low 02 (5%) treatments were achieved by diluting air with bottled N2. CO2 levels (350 and 1000 ,ul L-1) were maintained by the Phytotron's computer-controlled CO2 injection system. Sampling ports on the sides of the chambers permitted sequential harvesting without substantial loss of control over gas compo- Harvest data were analyzed using one-way ANOVA and the significance values were determined using Fisher's LSD multiple comparison test at the 0.05 level. 02 and CO2 effects on harvest data were compared at the 0.05 significance level using two-way ANOVA. All analyses were performed using Number Cruncher Statistical System (7) statistical software. RESULTS

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Section: Discussionmentioning

confidence: 91%

Response of Two Wheat Cultivars to CO₂ Enrichment under Subambient Oxygen Conditions

Musgrave¹,

Strain²

1988

Plant Physiol.

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“…Previous reports document an unexpected inhibition of seed production when plants are grown at low external oxygen, with a critical oxygen pressure of around 5% (v/v) external oxygen (compared with 21% [v/v] in ambient conditions; Hardy, 1975, 1976;Sinclair et al, 1987). More detailed analyses using series of subambient oxygen tensions revealed a linear decrease in Arabidopsis seed size when external oxygen was decreased below 15% (v/v;Porterfield et al, 1999), and a progressive arrest in Arabidopsis embryo development and inhibition of protein body formation when atmospheric oxygen was decreased below 16% (Kuang et al, 1998).…”

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confidence: 99%

Lipid Storage Metabolism Is Limited by the Prevailing Low Oxygen Concentrations within Developing Seeds of Oilseed Rape

et al. 2003

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The aim of this study was to investigate whether endogenous restrictions in oxygen supply are limiting for storage metabolism in developing oilseed rape (Brassica napus) seeds. Siliques were studied 30 d after flowering, when rapid lipid accumulation is occurring in the seeds. (a) By using microsensors, oxygen concentrations were measured within seeds and in the silique space between seeds. At ambient external oxygen (21% [v/v]) in the light, oxygen fell to 17% (v/v) between and 0.8% (v/v) within seeds. A step-wise reduction of the external oxygen concentration led within 2 h to a further decrease of internal oxygen concentrations, and a step-wise increase of the external oxygen concentration up to 60% (v/v) resulted in an increase in internal oxygen that rose to 30% (v/v) between and 8% (v/v) within seeds. (b) The increase in oxygen levels in the seeds was accompanied by a progressive increase in the levels of ATP, UTP, and the ATP to ADP and UTP to UDP ratios over the entire range from 0% to 60% (v/v) external oxygen. (c) To investigate metabolic fluxes in planta, 14 C-sucrose was injected into seeds, which remained otherwise intact within their siliques. The increase in oxygen in the seeds was accompanied by a progressive increase in the rate of lipid (including triacylglycerol), protein and cell wall synthesis, and an increase in glycolytic flux over a range from sub-to superambient oxygen concentrations. In contrast to lipid synthesis, starch synthesis was not significantly increased at superambient oxygen levels. The levels of fermentation products such as lactate and glycerol-3P increased only at very low (0%-4% [v/v]) external oxygen concentrations. (d) When 14 C-acetate or 14 C-acetyl-coenzyme A (CoA) was injected into seeds, label incorporation into triacylglycerol progressively increased over the whole range of external oxygen concentrations from 0% to 60% (v/v). (e) Stimulation of lipid synthesis was accompanied by an increase in sugar levels and a decrease in the levels of hexose-phosphates and acetyl-CoA, indicating sucrose unloading and the use of acetyl-CoA as possible regulatory sites. (f) Increased lipid synthesis was also accompanied by an increase in the maximal activities of invertase and diacylglycerol acyltransferase. (g) The developmental shift from starch to lipid storage between 15 and 45 d after flowering was accompanied by an increase in the seed energy state. (h) The results show that at ambient oxygen levels, the oxygen supply is strongly limiting for energy metabolism and biosynthetic fluxes in growing rape seeds, affecting lipid synthesis more strongly than starch synthesis. The underlying mechanisms and implications for strategies to increase yield and storage product composition in oilseed crops are discussed.Plants synthesize reduced carbon compounds from inorganic matter during photosynthesis in leaves, which are then exported to reproductive organs to be used for storage and growth. In developing seeds, Suc is converted to oil, protein, and starch, which are laid down as stor...

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“…Our conclusion is not contradicted by the results of 02 enrichment studies. Testing the suffocation hypothesis, Sinclair et al (21) doubled the PO2 in the atmosphere around field grown soybean plants but found no consistent increase in seed dry weight. Effects of high PO2 have to be regarded with caution, since O2 is toxic at high PO2, due to the increased formation of free radicals (8).…”

Section: Discussionmentioning

confidence: 99%

“…Several authors have suggested that seed growth and respiration are limited by 02 diffusion into the seed (9,16,20,21). Oxygen partial pressure (kPa) high sensitivity of seed 02 uptake to PO2 in the range of 20 to 21 kPa.…”

Section: Discussionmentioning

confidence: 99%

“…Ohmura and Howell (15,16) were the first to suggest that 02 uptake by the cotyledons of soybean seeds during maturation may be limited by 02 diffusion through the seed coat. Recently, Sinclair (20,21) has argued that 02 diffusion into the vascular vessels of soybean seed coats forms a potential limitation to seed respiration and growth. Gale (9) has shown that the CO2 evolution of intact soybean seeds is decreased by 02 partial pressures below ambient (<21 kPa), and suggests that the pod wall and seed coat constitute a barrier to the diffusion Of 02.…”

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Control of Seed Respiration and Growth in Vicia faba by Oxygen and Temperature: No Evidence for an Oxygen Diffusion Barrier

Visser

Dekhuijzen²,

Verkerke³

1990

Plant Physiol.

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The rate of dry matter accumulation by seeds of Vicia faba L. cv. Minica increases with temperature in the range of 16 to 26°C.The duration of dry matter accumulation decreases with temperature, resulting in a decrease of final seed dry weight. In this study we test the hypothesis that a diffusion barrier for 02, located in the seed coat, inhibits seed respiration and growth. The rate Of 02 uptake of intact seeds and of excised embryos and seed coats (separated seeds) was measured in air and buffer at 16, 20, and/or 260C at various 02 concentrations and developmental stages. Oxygen uptake rates of intact seeds in buffer were only 9 to 15% of those in air. In buffer, the respiration rate of intact seeds decreased at a PO2 below air saturation (21 kilopascals), whereas separated seeds showed a decline of 02 uptake only below 80% of air saturation. In air, embryo excision had no effect on the sensitivity of seed respiration to PO2, at both 20 and 260C. In air at 200C, separated and intact seeds showed similar rates of 02 uptake. Oxygen uptake by intact seeds, both halfway and beyond the linear growth phase, showed a temperature coefficient Q1o of 2.3 and was insensitive to p02 in the range of 80 to 100% of ambient. These results indicate that V. faba seed respiration in air is not limited by the diffusion of 02 into the seed.Both the rate and duration of seed growth are important parameters in yield formation in grain crops (13) and grain legumes (4, 6, 10). Cell division is an important process determining seed growth (5, 7, 10). One of the main environmental factors affecting these processes is temperature (4, 6, 13).The cause and mechanism of the cessation of seed growth in cereals and legumes are not known (5,6,10,13,20,23). With increasing growth temperature (16-26°C), the rate of dry matter accumulation in the seed of Vicia faba increases, but the duration of seed growth decreases. The combined effect is a lower final seed dry weight as temperature increases (4). Similar effects of temperature on seed growth have been reported for soybean (6) and wheat (13). The growth duration of Vicia embryos in vivo is similarly affected by temperature as in vitro (4,5). This has also been found for seed growth rate in soybean by Egli and Wardlaw (6). Thus, the cause of both the cessation of seed growth and the lower final seed dry weight at high temperature may be sought in processes in the seed.The relationship between growth and respiration of devel-668 oping seeds has not received much attention (10,11,20). Ohmura and Howell (15,16) were the first to suggest that 02 uptake by the cotyledons of soybean seeds during maturation may be limited by 02 diffusion through the seed coat. Recently, Sinclair (20, 21) has argued that 02 diffusion into the vascular vessels of soybean seed coats forms a potential limitation to seed respiration and growth. Gale (9) has shown that the CO2 evolution of intact soybean seeds is decreased by 02 partial pressures below ambient (<21 kPa), and suggests that the pod wall and seed coat ...

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Soybean Seed Growth in Response to Long-Term Exposures to Differing Oxygen Partial Pressures

Cited by 18 publications

References 6 publications

Response of Two Wheat Cultivars to CO₂ Enrichment under Subambient Oxygen Conditions

Response of Two Wheat Cultivars to CO₂ Enrichment under Subambient Oxygen Conditions

Lipid Storage Metabolism Is Limited by the Prevailing Low Oxygen Concentrations within Developing Seeds of Oilseed Rape

Control of Seed Respiration and Growth in Vicia faba by Oxygen and Temperature: No Evidence for an Oxygen Diffusion Barrier

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Soybean Seed Growth in Response to Long-Term Exposures to Differing Oxygen Partial Pressures

Cited by 18 publications

References 6 publications

Response of Two Wheat Cultivars to CO2 Enrichment under Subambient Oxygen Conditions

Response of Two Wheat Cultivars to CO2 Enrichment under Subambient Oxygen Conditions

Lipid Storage Metabolism Is Limited by the Prevailing Low Oxygen Concentrations within Developing Seeds of Oilseed Rape

Control of Seed Respiration and Growth in Vicia faba by Oxygen and Temperature: No Evidence for an Oxygen Diffusion Barrier

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Response of Two Wheat Cultivars to CO₂ Enrichment under Subambient Oxygen Conditions

Response of Two Wheat Cultivars to CO₂ Enrichment under Subambient Oxygen Conditions