Photosynthesis and Respiration by the Flag Leaf and Components of the Ear During Grain Development In Wheat

Evans, Lisa; Rawson, HM

doi:10.1071/bi9700245

Cited by 209 publications

(106 citation statements)

References 20 publications

(20 reference statements)

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“…We conclude that quantitatively, photosynthate derived directly from soybean pod photosynthesis is of little significance for podfilling compared to the supply of assimilate from the leaves. These results are in marked contrast to those reported for several cereals (7,8,13,14,17) in which it was concluded that the reproductive structures contribute at least 30% of the photosynthate for grain-filling. As suggested by the gas exchange data, soybean reproductive structures are capable of photosynthetic CO2 uptake from the external atmosphere as evidenced by a light-induced uptake of 1'4CO2 (Table II).…”

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confidence: 56%

“…Net photosynthesis in the reproductive organs of cereals such as barley (17), wheat (8,14,17), rice (7), and oats (13) is relatively high, contributing as much as 50 to 75% of the photosynthate to the grain. In contrast, in plants such as Phaseollis vulgaris (5), cotton (6), and peas (9) the photosynthetic contribution of the reproductive organs is low compared to that of the leaves.…”

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ABSTRACTThe rates of C02 exchange and "'CO2 incorporation in the light and dark and the activities of several photosynthetic, photorespiratory, and respiratory enzymes of soybean (Glycine (8,14, 17), rice (7), and oats (13) (5), cotton (6), and peas (9) the photosynthetic contribution of the reproductive organs is low compared to that of the leaves. In recent studies from this laboratory with soybeans (15, 16) we have reported on several aspects of reproductive growth and development and have become interested in the photosynthetic contribution of the soybean pod to seed yield.

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Growth and Development of Soybean (Glycine max [L.] Merr.) Pods

Quebedeaux¹,

Chollet²

1975

Plant Physiol.

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The rates of C02 exchange and "'CO2 incorporation in the light and dark and the activities of several photosynthetic, photorespiratory, and respiratory enzymes of soybean (Glycine (8,14, 17), rice (7), and oats (13) (5), cotton (6), and peas (9) the photosynthetic contribution of the reproductive organs is low compared to that of the leaves. In recent studies from this laboratory with soybeans (15, 16) we have reported on several aspects of reproductive growth and development and have become interested in the photosynthetic contribution of the soybean pod to seed yield. In this investigation we examined CO2 exchange, "CO2 incorporation, and the activity of nonphotosynthetic and photosynthetic/ photorespiratory enzymes of soybean reproductive structures from anthesis to maturity.

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confidence: 99%

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Growth and Development of Soybean (Glycine max [L.] Merr.) Pods

Quebedeaux¹,

Chollet²

1975

Plant Physiol.

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“…In a recent study (Aggarwal et aL, unpublished), it was observed that the leaf 4' decreased to -2.0 MPa at flowering in irrigated wheat plants when dry matter production was at its peak and the flag leaf was most active (10,25). A similar change in water relations at flowering has also been observed in sorghum (12,24) and soybean (33).…”

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Differences in Water Relations and Physiological Characteristics in Leaves of Wheat Associated with Leaf Position on the Plant

Aggarwal¹,

Sinha²

1984

Plant Physiol.

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The seasonal change in leaf water potential and its components, stomatal resistance, specific leaf weight, photosynthesis rate, the activities of ribulose-1,5-bisphosphate carboxylase and nitrate reductase, and soluble proteins were measured in flag leaves (ninth from base in position), seventh and fifth leaves of wheat Trticam aestipum L. cv Kalyansona. Flag leaves had a lower water and solute potential and lower or equal turgor pressure than seventh and fifth leaves. These differences were found to be independent of environment. The rate of photosynthesis and nitrate reductase activity were always lower in fifth and seventh leaves than in flag leaf. The photosynthetic efficiency in flag leaves appeared to be associated with lower stomatal resistance and higher specific leaf weight. The relations between leaf water potential and relative water content showed a change with leaf position. This change possibly allows flag leaf to maintain its functional efficiency despite its lower water potential.The physiological activity ofa leaf, particularly photosynthesis, depends on leaf age, genotype, and assimilate demand by sinks in addition to effects of environment (1 1, 23, 32). Leaf water status influences all aspects of growth and development (2,13,22). At t' of -1.0 to -1.5 MPa, most physiological processes such as leaf expansion, stomatal conductance, photosynthesis rate, and nitrogen metabolism are reduced (5, 13).In a recent study (Aggarwal et aL, unpublished), it was observed that the leaf 4' decreased to -2.0 MPa at flowering in irrigated wheat plants when dry matter production was at its peak and the flag leaf was most active (10, 25). A similar change in water relations at flowering has also been observed in sorghum (12, 24) and soybean (33). These studies also indicated that though leaf 4 was reduced at flowering, the physiological activity of the leaf was not impaired, rather it was improved. This observation contrasts with earlier studies showing sensitivity of physiological processes to small decreases in water potential (4, 13). It is, therefore, necessary to study the various physiological activities simultaneously with water relations at different growth stages.In the present investigation, seasonal changes in 4', 4',, and P have been studied concurrently with the Phs, the activities of RUBISCO and NR, r, and SLW in flag leaf and lower leaves of wheat. Pressure-volume curves were made to determine any change in water relations associated with the change in leaf position. An 15, 1980. Fertilizer at a rate of 75:60:60 kg/ha N:P:K was broadcast in the field prior to sowing. After germination, the distance between plants was maintained at 2.5 to 3.0 cm. In 20-d-old plants, main stems that were to be used subsequently for the measurements, were tagged. The field was irrigated as per agronomic practice at crown

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“…The rate of sucrose movement through the pools, given the grain-filling rate under these conditions of 1.94 f 0.12 mg-' of grain d-' (Fisher, 1990), was taken to be 220 nmol h-I. This assumes that sucrose makes up 75% of the dry weight entering the grain and that 20% of it is lost by respiration (Evans and Rawson, 1970;Fisher, 1990).…”

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confidence: 99%