Stomatal behaviour and water movement through roots of wheat plants treated with abscisic acid

ABSTRACrPretreatment of soybean (Glycine max L. var Ransom) root systems with abscisic acid (ABA) ameliorates the deleterious effect of low temperatures on root hydraulic conductance. ABA treatment of root systems subsequently chilled to 10°C with shoots at 25°C resulted in higher leaf water potentials and lower stomatal resistances. If the root systems are left at 25C, ABA causes stomatal closure. Membrane alterations are suggested as a mechanism for the ABA action in plant response to chilling stress.Abscisic acid has been implicated in plant response to environmental stress. ABA accumulates in plants during water stress (8,21) and closes stomata when applied to the transpiration stream (15,16,19). ABA also plays a role in plant response to low temperature stress (2,17,18 that treatment of root systems with ABA reduces the decrease in the hydraulic conductance of root systems at low temperatures. MATERIALS AND METHODSSoybean plants (Glycine max L. var Ransom) were grown in environmental growth chambers under a 12-h photoperiod at 25C. The photosynthetic photon flux density at plant height was 600 gE m-2 s-'. Seeds were sown in plastic pots (7.5 x 30 cm) containing a 1:1 mixture of sand and Turface. The bottom of the pot was cut off and replaced with a single hole stopper. Plants were watered daily with alternate applications of halfstrength Hoagland solution and distilled H20. Plants were 21 to 25 d old with one fully expanded trifoliolate leaf at the time of the experiment.A stock solution containing 0.1 M ABA (Sigma ± cis-trans) in 95% ethanol was prepared and stored in the dark at 4°C. Treatment solutions were prepared with distilled H20 the day before the experiment and kept in the dark at 22°C. One and one-half hours prior to the beginning of the photoperiod, the holes in the pots were sealed and 100 ml of 50 AM ABA or 100 ml of distilled H20 (with equivalent amounts of ethanol) were added. After 1 h of treatment, the drainage holes were uncovered and the pots allowed to drain for 5 min. The holes of eight treated and eight nontreated plants were resealed and the pots randomly placed into a water bath cooled to 10°C. Thermocouples placed in the center of selected pots indicated that the roots reached 10°C in 15 min and that there was less than 0.5C variation in temperature among individual pots. One-half hour after cooling, the lights were turned on. The remaining ABA-treated and nontreated plants were left with both roots and shoots at 25°C.Stomatal resistances of the upper and lower leaf surface were measured every 2 h with a diffusion porometer (Delta Instruments). Because of a limitation in the number of plants which would fit into the water bath, plant wiltedness, a nondestructive technique, was used to measure plant water status. Plant wiltedness was measured every 2 h by placing a protractor behind the stem of the plant. The angle of the apical internode relative to the rest of the stem was recorded. Zero degress meant a completely turgid plant, whereas 1800 meant a completely wilted plant. Four ho...

“…This suggests that at 25C ABA is transported to the shoot causing stomatal closure. Similar results have been reported for wheat (3). The increase in stomatal resistance prevents (Fig.…”

supporting

confidence: 89%

Amelioration of Chilling-Induced Water Stress by Abscisic Acid-Induced Changes in Root Hydraulic Conductance

Markhart¹

1984

“…In Xanthium strumaruim L., ABA-induced stomatal oscillations also became more pronounced at high Ca (20). Similar ABA-induced oscillations have been reported for wheat (5). If (20,21), although more recent work indicates this enhanced sensitivity is not always seen (22).…”

Section: Methodssupporting

confidence: 69%

“…It is also possible that the correlation of oscillatory stomatal behavior with low N nutrition may involve ABA metabolism. ABA has also been associated with increased E and decreased root hydraulic conductance (5), and has been shown to accumulate in N deficient plant tissue (17). The similarity between oscillations produced by low N content (Fig.…”

Section: Methodsmentioning

confidence: 99%

The Effects of N Nutrition on the Water Relations and Gas Exchange Characteristics of Wheat (Triticum aestivum L.)

Morgan¹

1986

The purpose of this study was to characterize leaf photosynthetic and stomatal responses of wheat (Triticum aestivum L.) plants grown under two N-nutritional regimes. High-and low-N regimes were imposed on growth-chamber-grown plants by fertilizing with nutrient solutions containing 12 or I millimolar nitrogen, respectively. Gas-exchange measurements indicated not only greater photosynthetic capacity of high-N plants under well-watered conditions, but also a greater sensitivity of CO2 exchange rate and leaf conductance to CO2 and leaf water potential compared to low-N plants. Increased sensitivity of high-N plants was associated with greater tissue elasticity, lower values of leaf osmotic pressure and greater aboveground biomass. These N-nutritional-related changes resulted in greater desiccation (lowered relative water content) of high-N plants as leaf water potential fell, and were implicated as being important in causing greater sensitivity of high-N leaf gas exchange to reductions in water potential. Water use efficiency of leaves, calculated as CO2 exchange rate/transpiration, increased from 9.1 to 13 millimoles per mole and 7.9 to 9.1 millimoles per mole for high-and low-N plants as water became limiting. Stomatal oscillations were commonly observed in the low-N treatment at low leaf water potentials and ambient CO2 concentrations, but disappeared as CO2 was lowered and stomata opened. but was also more responsive to I, resulting in lower g as water became less available (24,27,30). Other work on cotton and tea has indicated an opposite response; decreased stomatal sensitivity to I associated with high N nutrition (15,17,19). Nitrogen nutrition was found to have little effect on stomatal response of Panicum maximum var trichoglume or rice (Oryza sativa L.) to changes in ' (10, 29).Stomatal closure resulting from water stress is apparently linked to ABA metabolism. The release and/or production of ABA in the mesophyll occurs in response to water stress in these cells (21). ABA then travels to the guard cells where its accumulation results in stomatal closure, and often, increased stomatal sensitization to C, (20)(21)(22). In the long run, water stress induced reductions in mesophyll photosynthetic capacity may affect stomatal conductance since reduced carbon compounds required for stomatal performance are synthesized in the mesophyll (7, 21).The purpose of the present study was to investigate further the effect of N nutrition on stomatal and photosynthetic response to I in wheat leaves in conjunction with investigations on N nutritional effects on internal plant water relations. Stomatal response to I will be assessed in terms of sensitivity of g to.and Ci. Effects of water stress on mesophyll photosynthetic capacity will be determined from C, response curves of CER. The objective of this analysis is to better understand the physiological nature of increased stomatal sensitivity of wheat gas exchange to water stress related to high N nutrition. MATERIALS AND METHODSPlant Material. Caryopses of 'Olaf...

“…A linear variable differential transducer (Chauvin Arnoux, LVDT-L100, Paris, France) was attached to the tip of each leaf (Davies et al, 1982) and connected to the datalogger. Measurements began when leaf 6 emerged above the enclosing sheath of the preceding leaf and was about 350 mm long, and lasted for 2 phyllocrons.…”

Section: Plant Culture and Leaf Growthmentioning

confidence: 99%

Temperature Affects Expansion Rate of Maize Leaves without Change in Spatial Distribution of Cell Length (Analysis of the Coordination between Cell Division and Cell Expansion)

Ben-Haj-Salah¹,

Tardieu²

1995

181

138

We have analyzed the way in which temperature affects leaf elongation rate of maize (Zea mays L.) leaves, while spatial distributions (observed at a given time) of cell length and of proportion of cells in DNA replication are unaffected. We have evaluated, in six growth chamber experiments with constant temperatures (from 13 to 34°C) and two field experiments with fluctuating temperatures, (a) the spatial distributions of cell length and of leaf elongation rate, and (b) the distribution of cell division, either by using the continuity equation or by flow cytometry. Leaf elongation rate was closely related to meristem temperature, with a common relationship in the field and in the growth chamber. Cell division and cell elongation occurred in the first 20 and 60 mm after the ligule, respectively, at all temperatures. Similar quantitative responses to temperature were observed for local cell division and local tissue expansion rates (common x intercept and normalized slope), and both responses were spatially uniform over the whole expanding zone (common time courses in thermal time). As a consequence, faster cell elongation matched faster cell division rate and faster elongation was compensated for by faster cell displacement, resulting in temperature-invariant profiles of cell length and of proportion of dividing cells. Cell-to-cell communication, therefore, was not necessary to account for coordination.