Stomatal response to humidity in common bean

 

 

Stomatal response to humidity in common bean (Phaseolus vulgaris): Implications for maximum transpiration rate, water-use efficiency and productivity.

by Comstock J. P., Ehleringer J. R. (1993)

in Australian Journal of Plant Physiology 20, 669–691. –

CrossRef |

http://www.publish.csiro.au/?paper=PP9930669

Abstract

Twelve common bean (Phaseolus vulgaris L.) cultivars were grown under greenhouse conditions to study the response of net photosynthesis (A) and transpiration (E) to variation in the leaf-to-air humidity gradient (v). Large differences were observed between cultivars in maximum rates of A and E. The variation in A correlated with both leaf nitrogen content and specific leaf area. Thin leaves had higher nitrogen contents per unit dry weight, but thick leaves had higher nitrogen content per unit surface area.

Photosynthetic nitrogen-use efficiency did not correlate with nitrogen content on either a mass or a surface area basis. Very little variation was found between cultivars in the sensitivity of total leaf conductance (g) to increasing v, when sensitivity was defined as the slope of ln(g) versus v (δln(g)/δv). No significant correlation existed between δln(g)/δv and variation in maximum conductance values.

Much steeper slopes (greater sensitivity) were found in the response of stomatal conductance alone (g_s) to the leaf-leaf surface humidity gradient (v_s). The sensitivity of stomatal response correlated positively with variation in maximum conductance among cultivars, and, since stomatal conductance was in series with a fixed boundary layer conductance, this positive correlation made possible the uniform sensitivity of g(_total) with respect to v(_leaf-air) despite the wide variation in g_max.

All cultivars reached their maximum E at very similar v values, and all showed a relatively constant E over a wide range of high v. The implications of this relative homeostasis in E are discussed in the context of possible hydraulic limitations on E.

Considerable recent interest has focussed on the use of carbon isotope discrimination (Δ) as a useful screening character in crop breeding programmes, and Δ has been found to correlate positively with yield in P. vulgaris. We found that Δ measured on bulk leaf tissue, positively correlated with both A_max and g_max between bean cultivars, but did not correlate with instantaneous measures of intercellular CO₂ (c_I) when v was held constant across all measurements.

This apparent discrepancy may be due, at least in part, to variation in leaf temperatures among cultivars under normal growing conditions. Leaf-energy-budget simulations indicated that the observed range of maximum leaf conductance at low v would generate up to 3.0ºC variation in leaf temperatures under field conditions of low to moderate windspeed.

Given the strong stomatal response to v, this variation in leaf temperature could cause variation in carbon isotope discrimination, which reflects long-term c_I values. Such a mechanism of producing variation in c_I would not be apparent in c_I measurements taken under cuvette conditions where leaf temperature was held constant.

See CSIRO

Full text doi:10.1071/PP9930669

 

Control of stomatal conductance

 

 

Control of stomatal conductance by leaf water potential in Hymenoclea salsola (T. & G.), a desert subshrub.

by Comstock J., Mencuccini M. (1998)

in Plant, Cell & Environment 21: 1029–1038. –

Wiley Online Library |PubMed |

http://onlinelibrary.wiley.com/doi/10.1046/j.1365-3040.1998.00353.x/full

Schematic of the whole-plant photosynthesis cuvette with root pressure chamber. The cuvette was constructed of acrylic plastic lined with Teflon film. Internal mixing fans generated air movement 10–100 times the rate of air flow through the cuvette for gas exchange measurements. Temperature control was achieved by both water channels in the acrylic chamber walls and small radiators in the internal air flow pathway. The root pressure chamber was made of carbon steel and rated for pressures up to 4·0 MPa. The pressure chamber lid and the compression plate were formed by two steel half-circles which could be fitted around the intact plant stem to compress a neoprene gasket. – http://api.onlinelibrary.wiley.com/asset/v1/doi/10.1046%2Fj.1365-3040.1998.00353.x/asset/image_n%2FPCE_353_f1.gif?l=q8hDySOaNttEIdDP9D42UhSPCn%2BHKzXqYVuA9SabmExnDhSJcb7YXXRak4%2FJruKxT60H5vf%2BOJL1eC1RUWKaBg%3D%3D&s=%22d695782fa0f9473cbd5dea6c705f7155%22&a=wol

Abstract

The role of leaf water potential in controlling stomatal conductance (g_s) was examined in the desert subshrub Hymenoclea salsola. For plants operating at high irradiance, stomatal closure in response to high leaf-air humidity gradient (D) was largely reversed by soil pressurization.

Stomatal re-opening eliminated, on average, 89% of the closure normally induced by high D. Transpiration rates (E) reached under these conditions were far higher than maximal rates normally observed at any point of the D response. In situ stem psychrometry indicated that water flux at all times conformed to a simple Ohm’s-law analogy.

Under conditions of high D, E increased substantially in response to soil pressurization.

Stomatal regulation did not constrain E during this treatment, but did result in nearly constant minimum leaf water potentials.

Read the full text: Wiley Online Library

Leaf water potential and stomatal conductance (gs)

Photo credit: Google

Control of stomatal conductance by leaf water potential in Hymenoclea salsola (T. & G.), a desert subshrub

by Comstock J. P., Mencuccini M. (1998)

in Plant, Cell & Environment 21: 1029–1038. – 

Abstract, Full Article (HTML), PDF(594K), References, Web of Science® Times Cited: 64.

(a) Stomata usually open in response to the blue light of sunlight. (b) Stomata usually close in response to lack of sunlight. They can also close during the day under conditions of water stress, which induces plants to produce more of the hormone abscisic acid (ABA). Stomatal guard cell plasma membranes possess ABA receptors, which receive the drought signal. – http://biology-forums.com/gallery/33_25_07_11_12_56_44.jpeg

Abstract

The role of leaf water potential in controlling stomatal conductance (g_s) was examined in the desert subshrub Hymenoclea salsola. For plants operating at high irradiance, stomatal closure in response to high leaf-air humidity gradient (D) was largely reversed by soil pressurization.

Stomatal re-opening eliminated, on average, 89% of the closure normally induced by high D. Transpiration rates (E) reached under these conditions were far higher than maximal rates normally observed at any point of the D response.

In situ stem psychrometry indicated that water flux at all times conformed to a simple Ohm’s-law analogy. Under conditions of high D, Eincreased substantially in response to soil pressurization. Stomatal regulation did not constrain E during this treatment, but did result in nearly constant minimum leaf water potentials.

The control of stomatal conductance and transpiration

Photo credit: Google

Hydraulic and chemical signalling in the control of stomatal conductance and transpiration

by Comstock J. P. (2002)

Jonathan P Comstock, Boyce Thompson Institute for Plant Research, Tower Road, Ithaca, NY 14853, USA.

in J. Exp. Bot.53(367): 195-200

(CrossRef, Medline).

Model for the role of signaling factors in stomatal closure and retrograde signaling during water stress. – Water stress adversely impacts many aspects of the physiology of plants, especially photosynthetic capacity. – http://www.frontiersin.org/files/Articles/76566/fpls-05-00086-r2/image_m/fpls-05-00086-g002.jpg

Abstract

Abscisic acid (ABA) transported in the xylem from root to shoot and perceived at the guard cell is now widely studied as an essential regulating factor in stomatal closure under drought stress. This provides the plant with a stomatal response mechanism in which water potential is perceived in the root as an indication of soil water status and available water resources.

There is also ample evidence that stomata respond directly to some component of leaf water status. This provides additional information about water potential gradients developing between root and shoot as the result of water transport, allowing for a more stable regulation of shoot water status and better protection of the transport system itself.

The precise location at which leaf water status is sensed, however, and the molecular events transducing this signal into a guard cell response are not yet known. Major questions therefore remain unanswered on how water stress signals perceived at root and leaf locations are integrated at the guard cell to control stomatal behaviour.

See the text: NCBI