Differing Sensitivity of Photosynthesis to Low Leaf Water Potentials in Corn and Soybean
TL;DR: It was concluded that the C(4) pathway confers no particular ability to withstand low leaf water potentials and corn was less able to withstand severe desiccation without tissue death.
Abstract: Rates of net photosynthesis were studied in soil-grown corn (Zea mays) and soybean (Glycine max) plants having various leaf water potentials. Soybean was unaffected by desiccation until leaf water potentials were below -11 bars. Rates of photosynthesis in corn were inhibited whenever leaf water potentials dropped below -3.5 bars.The differences in photosynthetic behavior could be attributed solely to differences in stomatal behavior down to leaf water potentials of -16 bars in soybean and -10 bars in corn. Below these potentials, other factors in addition to stomatal closure caused inhibition, although their effect was relatively small.Corn, which has the C(4)-dicarboxylic acid pathway for carbon fixation, generally had a higher rate of photosynthesis than soybean during desiccation. Nevertheless, since inhibition of photosynthesis began at higher potentials than in soybean, and since corn was less able to withstand severe desiccation without tissue death, it was concluded that the C(4) pathway confers no particular ability to withstand low leaf water potentials.
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TL;DR: An analysis of major U.S. crops shows that there is a large genetic potential for yield that is unrealized because of the need for better adaptation of the plants to the environments in which they are grown.
Abstract: An analysis of major U.S. crops shows that there is a large genetic potential for yield that is unrealized because of the need for better adaptation of the plants to the environments in which they are grown. Evidence from native populations suggests that high productivity can occur in these environments and that opportunities for improving production in unfavorable environments are substantial. Genotypic selection for adaptation to such environments has already played an important role in agriculture, but the fundamental mechanisms are poorly understood. Recent scientific advances make exploration of these mechanisms more feasible and could result in large gains in productivity.
3,715 citations
1,539 citations
TL;DR: The transient response of stomata to change in rate of evaporation may be a device which is designed to enhance the speed of the response to light.
Abstract: Publisher Summary Stomata1 movement is a manifestation of strain in the epidermis, associated with change in the hydraulic pressure in the epidermal cells. This chapter discusses the role and behavior of stomata in the hydrology of the soil–plant–atmosphere system. Stomata operate in the light in such a way as to maintain positive turgor in the leaves, in the majority of crop plants and other species. The transient response of stomata to changes in environment which cause rapid changes in plant–water relations is quite dramatic. The nature of the stomatal response to change in water potential must involve the mechanical and hydraulic attributes of the stomatal apparatus. There is only a tenuous relationship between the potential of water in leaf tissue in bulk and the local potential of water to which an individual stoma responds in ways, which are also discussed. Thus the transient response of stomata to change in rate of evaporation may be a device which is designed to enhance the speed of the response to light.
724 citations
TL;DR: Osmotic adjustment has long been known as a means by which higher plants adapt to salinity, with much of the cell osmotica being ionic and accumulated from the medium.
Abstract: Many plant processes are affected by mild water stress, with cell growth probably the most sensitive. Except for turgor-mediated processes, the physicochemical basis for the transduction of small changes in water status into alterations in metabolism remains obscure. Turgor pressure is assigned a critical role in cell growth: the physical force needed to sustain enlargement. Simple physical models relating growth to turgor are conceptually useful in examining effects of water stress but can be misleading because metabolic and regulatory responses may be marked and vary temporally. Osmotic adjustment has long been known as a means by which higher plants adapt to salinity, with much of the cell osmotica being ionic and accumulated from the medium. Though not generally recognized, osmotic adjustment also appears to be an important mechanism for adaptation to water-limiting conditions, even in mesophytic plants. In this case much of the osmotica might possibly be internally generated. Recent field data on seasonal and diurnal adjustment and vertical water-potential gradients in plant canopies are discussed relative to growth and water-potential components.
698 citations
TL;DR: Results are interpreted as the signature of a transition from source to sink growth limitation under water deficit, suggesting release of the influence of C availability on sink organ growth.
Abstract: In plants, carbon (C) molecules provide building blocks for biomass production, fuel for energy, and exert signalling roles to shape development and metabolism. Accordingly, plant growth is well correlated with light interception and energy conversion through photosynthesis. Because water deficits close stomata and thus reduce C entry, it has been hypothesised that droughted plants are under C starvation and their growth under C limitation. In this review, these points are questioned by combining literature review with experimental and modelling illustrations in various plant organs and species. First, converging evidence is gathered from the literature that water deficit generally increases C concentration in plant organs. The hypothesis is raised that this could be due to organ expansion (as a major C sink) being affected earlier and more intensively than photosynthesis (C source) and metabolism. How such an increase is likely to interact with C signalling is not known. Hence, the literature is reviewed for possible links between C and stress signalling that could take part in this interaction. Finally, the possible impact of water deficit-induced C accumulation on growth is questioned for various sink organs of several species by combining published as well as new experimental data or data generated using a modelling approach. To this aim, robust correlations between C availability and sink organ growth are reported in the absence of water deficit. Under water deficit, relationships weaken or are modified suggesting release of the influence of C availability on sink organ growth. These results are interpreted as the signature of a transition from source to sink growth limitation under water deficit.
620 citations
Cites background from "Differing Sensitivity of Photosynth..."
...The maintenance of photosynthesis under water deficit has been repeatedly reported (Boyer, 1970b; Quick et al., 1992; Bogeat-Triboulot et al., 2007)....
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...In contrast, water deficit strongly reduces leaf or shoot expansion rates (Boyer, 1970a; Hsiao, 1973; Ben Haj Salah and Tardieu, 1997; Tardieu et al., 1999, 2000)....
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01 Jan 1959
TL;DR: In this article, the effect of light intensity, leaf temperature, and C0 2 concentration on photosynthetic rate in leaves of crop plants was estimated in absolute units, which allowed quantitative comparison of micrometeorological and physiological effects on photosynthesis.
Abstract: The effect was estimated of light intensity, leaf temperature, and C0 2 concentration on photosynthetic rate in leaves of crop plants. The potential capacities of photochemical and biochemical processes and of C0 2 transport were compared. Resistance to C0 2 transport in various parts of the pathway from external air to reaction centre in the chloroplasts was estimated in absolute units. This allowed quantitative comparison of micrometeorological and physiological effects on photosynthesis. C0 2 transport towards the leaf is affected by the sum of resistances in external air (r a ), stomata (r s ), and mesophyll cells (r m ). Since r m is usually larger than r s of open stomata, r m is probably an important yield determining factor. With adequate water-supply, transpiration depends on r s + r a , but not on r m . Therefore higher values of r s and lower values of r m favour the water balance of crops. With strong light and leaf temperature around 22°C, C0 2 saturation of photosynthesis was reached with C0 2 concentrations between 01 and 0.15 %. Techniques were described for accurate measurement of C0 2 and water vapour, leaf temperature, light intensity and diffusion resistance. The importance of different types of light bulbs for photosynthesis was evaluated, and much attention was paid to accurate assessment of effective C0 2 concentration in the air around leaves in assimilation chambers.
580 citations
TL;DR: Although leaf enlargement did not occur initially, enlargement resumed toward the end of the desiccation period, however, the rate of enlargement was not as rapid as in the well watered control, nor did it return to the control rate when the plant was rewatered.
Abstract: Rates of photosynthesis, dark respiration, and leaf enlargement were studied in soil-grown corn (Zea mays), soybean (Glycine max), and sunflower (Helianthus annuus) plants at various leaf water potentials. As leaf water potentials decreased, leaf enlargement was inhibited earlier and more severely than photosynthesis or respiration. Except for low rates of enlargement, inhibition of leaf enlargement was similar in all three species, and was large when leaf water potentials dropped to about -4 bars.Intact sunflower leaves were held for 4 days at leaf water potentials which permitted maximal photosynthesis and respiration, but which inhibited leaf enlargement. Although leaf enlargement did not occur initially, enlargement resumed toward the end of the desiccation period. However, the rate of enlargement was not as rapid as in the well watered control, nor did it return to the control rate when the plant was rewatered.
557 citations
TL;DR: * Supported by grants G 24052 and GE 3612 from the National Science Foundation.
Abstract: * Supported by grants G 24052 and GE 3612 from the National Science Foundation. 1 Beauchesne, G., M. Leboeuf, and R. Goutarel, in Regulateurs Naturels de la Croissance Vegtale (Paris: Centre National de la Recherche Scientifique, 1964), p. 119. 2 Letham, D. A., in Regulateurs Naturels de la Croissance Vegetale (Paris: Centre National de la Recherche Scientifique, 1964), p. 109; and ref. 6 (below). 3Miller, C. O., these PROCEEDINGS, 47, 170 (1961); and refs. 13 and 16 (below). 4Letham, D. S., and C. 0. Miller, Plant Cell Physiol., in press. 6 Letham, D. S., J. S. Shannon, and I. R. McDonald, Proc. Chem. Soc., 1964, 230. 6 Letham, D. S., Life Sci., 2, 569 (1963). 7 Kefford, K. P., Science, 142, 1495 (1963). 8 Miller, C. O., in Modern Methods of Plant Analysis (Berlin: Springer-Verlag, 1963), vol. 6, p. 194. 9 McCalla, D. R., D. J. Moore, and D. Osborne, Biochim. Biophys. Acta, 55, 522 (1962). 10 Hurlbert, R. B., H. Schmitz, A. F. Brumm, and V. R. Potter, J. Biol. Chem., 209, 23 (1954). 11 Jacobson, K. B., Science, 138, 515 (1962). 12 Khym, J. X., and W. E. Cohn, J. Am. Chem. Soc., 76, 1818 (1954). 13 Miller, C. O., Plant Physiol., 37, xxxv (1962). 14 Loeffier, J. E., and J. Van Overbeek, in Regulateurs Naturels de la Croissance V~ggtale (Paris: Centre National de la Recherche Scientifique, 1964), p. 77. 15 Fox, J. E., Plant Physiol., 39, xxxi (1964). 16 Miller, C. O., and F. H. Witham, in Rlgulateurs Naturels de la Croissance V~ggtale (Paris: Centre National de la Recherche Scientifique, 1964), p. I (erratum).
343 citations
TL;DR: It was concluded that, although stem characteristics may affect the measurements, pressure chamber determinations were sufficiently close to psychrometer measurements that the pressure chamber may be used for relative measurements of leaf water potentials, especially in sunflower and yew.
Abstract: Leaf water potentials were estimated from the sum of the balancing pressure measured with a pressure chamber and the osmotic potential of the xylem sap in leafy shoots or leaves. When leaf water potentials in yew, rhododendron, and sunflower were compared with those measured with a thermocouple psychrometer known to indicate accurate values of leaf water potential, determinations were within +/- 2 bars of the psychrometer measurements with sunflower and yew. In rhododendron. water potentials measured with the pressure chamber plus xylem sap were 2.5 bars less negative to 4 bars more negative than psychrometer measurements.The discrepancies in the rhododendron measurements could be attributed, at least in part, to the filling of tissues other than xylem with xylem sap during measurements with the pressure chamber. It was concluded that, although stem characteristics may affect the measurements, pressure chamber determinations were sufficiently close to psychrometer measurements that the pressure chamber may be used for relative measurements of leaf water potentials, especially in sunflower and yew. For accurate determinations of leaf water potential, however, pressure chamber measurements must be calibrated with a thermocouple psychrometer.
339 citations
285 citations