Abstract
Photosynthetic parameters, growth, and pigment contents were determined during expansion of the fourth leaf of in vitro photoautotrophically cultured Nicotiana tabacum L. plants at three irradiances [photosynthetically active radiation (400-700 nm): low, LI 60 µmol m-2 s-1; middle, MI 180 µmol m-2 s-1; and high, HI 270 µmol m-2 s-1]. During leaf expansion, several symptoms usually accompanying leaf senescence appeared very early in HI and then in MI plants. Symptoms of senescence in developing leaves were: decreasing chlorophyll (Chl) a+b content and Chl a/b ratio, decreasing both maximum (FV/FM) and actual (ΦPS2) photochemical efficiency of photosystem 2, and increasing non-photochemical quenching. Nevertheless, net photosynthetic oxygen evolution rate (P N) did not decrease consistently with decrease in Chl content, but exhibited a typical ontogenetic course with gradual increase. P N reached its maximum before full leaf expansion and then tended to decline. Thus excess irradiance during in vitro cultivation did not cause early start of leaf senescence, but impaired photosynthetic performance and Chl content in leaves and changed their typical ontogenetic course.
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Claims 5
Claim · model-written summary
Senescence symptoms appeared early under high irradiance and later under middle irradiance.
- Taxon
- Nicotiana tabacum L.
Nicotiana tabacume1 - Organ / stage
- leafe0
- Treatment
- HIe0
- Outcome
- symptoms usually accompanying leaf senescencee0
- Direction
- very earlye0
- Comparator
- MIe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“During leaf expansion, several symptoms usually accompanying leaf senescence appeared very early in HI and then in MI plants.”
e1“Nicotiana tabacum L. plants at three irradiances [photosynthetically active radiation (400-700 nm): low, LI 60 µmol m-2 s-1; middle, MI 180 µmol m-2 s-1; and high, HI 270 µmol m-2 s-1]”
Claim · model-written summary
Developing leaves showed declining chlorophyll content and ratio and photosystem 2 efficiency, with rising non-photochemical quenching.
- Taxon
- Nicotiana tabacum L.Nicotiana tabacume1
- Organ / stage
- developing leavese0
- Outcome
- chlorophyll (Chl) a+b content and Chl a/b ratioe0
- Direction
- decreasinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Symptoms of senescence in developing leaves were: decreasing chlorophyll (Chl) a+b content and Chl a/b ratio, decreasing both maximum (FV/FM) and actual (ΦPS2) photochemical efficiency of photosystem 2, and increasing non-photochemical quenching.”
e1“Nicotiana tabacum L. plants at three irradiances”
Claim · model-written summary
Net photosynthetic oxygen evolution did not consistently decrease with chlorophyll content.
- Taxon
- Nicotiana tabacum L.Nicotiana tabacume1
- Compound
- Chle0
- Outcome
- net photosynthetic oxygen evolution rate (P N)e0
- Direction
- did not decrease consistentlye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“net photosynthetic oxygen evolution rate (P N) did not decrease consistently with decrease in Chl content”
e1“Nicotiana tabacum L. plants at three irradiances”
Claim · model-written summary
Net photosynthetic oxygen evolution rose during leaf expansion, peaked before full expansion and then tended to decline.
- Taxon
- Nicotiana tabacum L.Nicotiana tabacume2
- Organ / stage
- leaf expansione0
- Outcome
- P Ne0
- Direction
- gradual increasee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“P N reached its maximum before full leaf expansion and then tended to decline.”
e1“typical ontogenetic course with gradual increase”
e2“Nicotiana tabacum L. plants at three irradiances”
Claim · model-written summary
Excess irradiance impaired photosynthetic performance and chlorophyll content and changed their ontogenetic course, without starting senescence early.
- Taxon
- Nicotiana tabacum L.Nicotiana tabacume1
- Organ / stage
- leavese0
- Treatment
- excess irradiancee0
- Outcome
- photosynthetic performance and Chl contente0
- Direction
- impairede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Thus excess irradiance during in vitro cultivation did not cause early start of leaf senescence, but impaired photosynthetic performance and Chl content in leaves and changed their typical ontogenetic course.”
e1“Nicotiana tabacum L. plants at three irradiances”
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