Abstract
In studies about the photosynthesis response to en vironmental stresses, such as drought, the Rubisco specificity factor (t) is assumed to be constant or derived indirectly from gas exchange measurements. However, an analysis of the acclimation of x to drought using in vitro determinations is lacking. The aim of the present work was to analyse the acclimation of t to different drought intensities in tobacco (Nicotiana taba cum L). Potted tobacco plants were subjected to three different water regimes (100%, 40%, and 15% of field capacity) and new leaves were allowed to develop. When acclimated leaves were fully developed, they were sampled for gas exchange and chlorophyll fluo rescence measurements, as well as for the in vitro analysis of Rubisco kinetic properties. Relative water content and gas exchange decreased with increasing water shortage. The apparent Rubisco specificity factor as estimated in vivo by gas exchange decreased with water stress. However, in vitro estimates of x were identical among treatments, as were Rubisco specific initial activity and activation state. The reasons for the observed discrepancy between in vitro and in vivo estimates are profusely discussed. It is suggested that the Rubisco specificity factor does not acclimate to water stress in the short term (weeks or months) in tobacco, and the validity of the so-called Laisk gas exchange method to estimate x under drought is questioned.
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Claims 6
Claim · model-written summary
In tobacco, relative water content and gas exchange decreased with increasing water shortage.
- Taxon
- tobacco
Nicotiana tabacumt0 - Treatment
- water shortagee0
- Outcome
- Relative water content and gas exchangee0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Relative water content and gas exchange decreased with increasing water shortage”
t0“to drought in tobacco”
Claim · model-written summary
The apparent Rubisco specificity factor estimated in vivo by gas exchange decreased with water stress in tobacco.
- Taxon
- tobaccoNicotiana tabacumt0
- Treatment
- water stresse0
- Outcome
- apparent Rubisco specificity factore0
- Direction
- decreasede0
- Qualifier
- estimated in vivo by gas exchangee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The apparent Rubisco specificity factor as estimated in vivo by gas exchange decreased with water stress”
t0“to drought in tobacco”
Claim · model-written summary
In vitro estimates of the Rubisco specificity factor were identical among the water treatments in tobacco.
- Taxon
- tobaccoNicotiana tabacumt0
- Treatment
- three different water regimes (100%, 40%, and 15% of field capacity)e1
- Outcome
- in vitro estimates of xe0
- Direction
- identicale0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in vitro estimates of x were identical among treatments”
e1“three different water regimes (100%, 40%, and 15% of field capacity)”
t0“to drought in tobacco”
Claim · model-written summary
Rubisco specific initial activity and activation state were also identical among the water treatments in tobacco.
- Taxon
- tobaccoNicotiana tabacumt0
- Treatment
- three different water regimes (100%, 40%, and 15% of field capacity)e1
- Outcome
- Rubisco specific initial activity and activation statee0
- Direction
- no_changeinferrede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“as were Rubisco specific initial activity and activation state”
e1“three different water regimes (100%, 40%, and 15% of field capacity)”
t0“to drought in tobacco”
Claim · model-written summary
The authors suggest that the Rubisco specificity factor does not acclimate to water stress in tobacco in the short term (weeks or months).
- Taxon
- tobaccoNicotiana tabacume0
- Treatment
- water stresse0
- Outcome
- Rubisco specificity factore0
- Direction
- no_changeinferrede0
- Qualifier
- short term (weeks or months)e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the Rubisco specificity factor does not acclimate to water stress in the short term (weeks or months) in tobacco”
Claim · model-written summary
The authors question the validity of the Laisk gas exchange method for estimating the Rubisco specificity factor under drought.
- Taxon
- tobaccoNicotiana tabacumt0
- Outcome
- validity of the so-called Laisk gas exchange methode0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the validity of the so-called Laisk gas exchange method to estimate x under drought is questioned”
t0“to drought in tobacco”
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