The After‐Effect of Water Stress on Chlorophyll Formation during Greening and the Levels of Abscisic Acid and Proline in Dark Grown Wheat Seedlings

Abstract

Cut seedlings of wheat plants {Triticum aestivum L, cv, Starke II Weibull) between 6 and 7 days old were water stressed in darkness by exposing them to air of 35% relative humidity 2,5 to 20 h. This treatment resulted in a water potential of -11 bars in the leaves after 20 h. The leaves were then rewatered and irradiated. The chlorophyll formation that took place in fully turgid leaves during the greening was markedly decreased in the case of the water-stress pretreatment, and especially the lag phase was prolonged. The longer the stress pretreatment the more evident was the subsequent effect on chlorophyll formation. However, no linear relationship was found between the amount of stress and the chlorophyll content. Protoehlorophyllide regeneration from endogenously formed ^aminolevulinic acid was markedly decreased even after the shortest water-stress period. However, protoehlorophyllide accumulation from exogenously supplied ^-aminolevulinic acid was only slightly decreased following the water-stress pretreatment, Eurthermore, the ratio of protochlorophyllide^jo to protochlorophyllide^^s was slightly reduced by the same conditions.During the stress period both abscisic acid and proline were accumulated in the leaves. The content of abscisic acid increased up to six times the normal level during water stress lasting for 20 h. The increase of proline was about three-fold for similar treatment. After rewatering the leaves the levels of both abscisic acid and proline rapidly declined and reached, 10 h later, the levels found in unstressed seedlings.The increase in abscisic acid during water stress associated with impaired chlorophyll metabolism suggested that the after-effect of water stress might be linked to chlorophyll metabolism through abscisic acid or some of its metabolites. The changes in proline content open the possibility that this substance could function as a reserve substance for the formation of chlorophyll after the discontinuation of the stress. 206CURT BENGTSON ET AL.

Ecophysiology of Limonium axillare and Avicennia marina from the coastline of Arabian Gulf-Qatar

“…Mg 2+ is an important element occupying a central position in the chlorophyll molecule, thereby affecting the concentration of chlorophylls a and b in the green plant tissues . In fact, the results of the present study revealed that the photosynthetic pigments contents were less than those reported for many glycophytes (Bengtson et al 1987;Alhadi et al 1999;Yasseen 2001). Na + and Cl − may interfere with the accumulation of macronutrients, by inhibiting H + -ATPase of plasma membranes and consequently inhibit the protein transporters leading to nutrient imbalance (Fukuda et al 1998).…”

High salt stress in wheat leaves causes retardation of chlorophyll accumulation due to a limited rate of protochlorophyllide formation

“…The Pchlide with fluorescence emission at 655 nm is rapidly transformed to Chlide when the dark‐grown leaves are irradiated. Different stress conditions are known to decrease the fluorescence emission at 655 nm and increase the emission at 633 nm (Bengtson et al 1978, Le Lay et al 2001) leading to a reduced accumulation of chlorophyll (Bengtson et al 1978, Duysen and Freeman 1974). The inhibition of the chlorophyll accumulation after salt treatment could be expected to be dependent on a reduced content of Pchlide fluorescing at 655 nm.…”

“…Small variations in the peak position of the long‐wavelength Pchlide form were found to be species dependent (Böddi et al 1992, Amirjani and Sundqvist 2006). Factors such as phytohormones, drought and leaf age influence the proportion between long‐wavelength and short‐wavelength Pchlide forms (Bengtson et al 1977, 1978, Schoefs and Franck 1993, Schoefs et al 2000).…”

Endogenous levels of abscisic acid and indole-3-acetic acid during in vitro rooting of Wild Cherry explants produced by micropropagation

“…Leaves which represent the major visible organs in the apical zone (82% of apical sample dry weight), may be mainly responsible for the ABA variations during the first week of culture [3] . Leaves which represent the major visible organs in the apical zone (82% of apical sample dry weight), may be mainly responsible for the ABA variations during the first week of culture [3] .…”