Vol. 71 No: 3

Title:
Dynamic Effects of Changes in Electric Conductivity on Transpiration and Growth of Greenhouse-Grown Tomato Plants

Author:
W. VAN IEPEREN

pp: 481-496

Abstract:
The dynamic responses of the rates of growth and transpiration of greenhouse grown tomato plants (Lycopersicon esculentum Mill. cv. Counter) were investigated in relation to changes in the osmotic potential in the root environment (ψ_π^re). Once a day, ψ_π^re was alternated between -0.01 (high) and -0.36 MPa (low). Changes in ψ_π^re were conducted in the light or the dark. Rates of water uptake (U) and transpiration (E) were simultaneously measured on the same plant, growing in water culture under natural light. The accuracy of measured E and U was sufficient to calculate changes in plant water content (WC^P) on a per-minute base. Courses of WC^P were analysed, and changes in WC^P attributed to growth and to alterations in plant water deficits. During large parts of the dark period the course of WCP was linear and changes in WC^P were completely attributable to irreversible growth. During the light period, WC^P fluctuated with changes in global radiation and associated E, while increasing. These fluctuations in WC^P as well as transient changes in WC^P immediately after ψ_π^re changes in the dark were attributed to changes in plant water deficit. At low ψ_π^re, the growth rate was lower, and plant water deficits were higher, than at high ψ_π^re. Growth rate changed almost immediately upon changes in psi;_π^re. Changes in growth rate were initially larger when a change in ψ_π^re was implemented in the dark than when it was implemented in the light. These initially larger responses were partially counterbalanced during the following light period, indicating adaptation of the plant during the light. E during the light was hardly influenced by the applied ψ_π^re levels. In the dark, E decreased after a change in ψ_π^re high to low, while it increased after the opposite ψ_π^re change. However, the differences in E were minimal. At low ψ_π^re plant water deficits increased more with increasing E than at high ψ_π^re. Within both ψ_π^re levels, hysteresis was observed on the relation between E and plant water deficit over a day. At a similar transpiration rate, plant water deficit was higher in the afternoon than in the morning. The hysteresis effect was more pronounced at low ψ_π^re.

Full text: JHSB Subscribers     ISHS members & other users
(PDF 1065091 bytes)

Translate:

Go back to previous page