An evaluation of the effects of exogenous ethephon, an ethylene releasing compound, on photosynthesis of mustard Brassica juncea cultivars that differ in photosynthetic capacityReportar como inadecuado




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BMC Plant Biology

, 4:21

First Online: 30 December 2004Received: 30 August 2004Accepted: 30 December 2004

Abstract

BackgroundThe stimulatory effect of CO2 on ethylene evolution in plants is known, but the extent to which ethylene controls photosynthesis is not clear. Studies on the effects of ethylene on CO2 metabolism have shown conflicting results. Increase or inhibition of photosynthesis by ethylene has been reported. To understand the physiological processes responsible for ethylene-mediated changes in photosynthesis, stomatal and mesophyll effects on photosynthesis and ethylene biosynthesis in response to ethephon treatment in mustard Brassica juncea cultivars differing in photosynthetic capacity were studied.

ResultsThe effects of ethephon on photosynthetic rate PN, stomatal conductance gS, carbonic anhydrase CA activity, 1-aminocyclopropane carboxylic acid synthase ACS activity and ethylene evolution were similar in both the cultivars. Increasing ethephon concentration up to 1.5 mM increased PN, gS and CA maximally, whereas 3.0 mM ethephon proved inhibitory. ACS activity and ethylene evolution increased with increasing concentrations of ethephon. The corresponding changes in gs and CA activity suggest that the changes in photosynthesis in response to ethephon were triggered by altered stomatal and mesophyll processes. Stomatal conductance changed in parallel with changes in mesophyll photosynthetic properties. In both the cultivars ACS activity and ethylene increased up to 3.0 mM ethephon, but 1.5 mM ethephon caused maximum effects on photosynthetic parameters.

ConclusionThese results suggest that ethephon affects foliar gas exchange responses. The changes in photosynthesis in response to ethephon were due to stomatal and mesophyll effects. The changes in gS were a response maintaining stable intercellular CO2 concentration Ci under the given treatment in both the cultivars. Also, the high photosynthetic capacity cultivar, Varuna responded less to ethephon than the low photosynthetic capacity cultivar, RH30. The photosynthetic capacity of RH30 increased with the increase in ethylene evolution due to 1.5 mM ethephon application.

AbbrevationsAdometS-adenosyl methionine

ACS1-aminocyclopropane carboxylic acid synthase

CAcarbonic anhydrase

Ciintercellular CO2 concentration

gSstomatal conductance

PNnet photosynthetic rate

Electronic supplementary materialThe online version of this article doi:10.1186-1471-2229-4-21 contains supplementary material, which is available to authorized users.

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Autor: NA Khan

Fuente: https://link.springer.com/







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