External calcium requirements for light induction of chlorophyll accumulation and its enhancement by red light and cytokinin pretreatments in excised etiolated cucumber cotyledons

Abstract

Abstract. Excised etiolated cucumber (Cucumis sativus L.) cotyledons that were depleted of external Ca 2 + by equilibration with a Ca 2 + buffer, which maintained the free Ca 2+ concentration at 10 -8 M, failed to accumulate chlorophyll upon a 2-h exposure to white light. Increasing amounts of chlorophyll accumulation occurred at increasing external Ca 2+ concentrations within the range of 10-7-10-3 M. Preillumination with red light or pretreatment with benzyladenine, which enhanced the rate of light-induced chlorophyll accumulation in control cotyledons, did not overcome the block to light-induced chlorophyll accumulation caused by the depletion of external Ca 2 +. Etiolated cotyledons that were treated with the Ca 2 § ionophore, A23187, and then equilibrated with 10-5M Ca 2+, accumulated significantly more chlorophyll during exposure to light than did untreated cotyledons. The enhancing effect of A23187 was approximately equal to that caused by red-light pretreatment. Etiolated cotyledons that were exposed to the Ca 2+-channel-blocking agent, Nd 3 + (neodymium), in the presence of 10-s M Ca 2 +, did not exhibit an enhancement of chlorophyll accumulation by red-light pretreatment, although they accumulated control levels of chlorophyll upon exposure to light and showed control levels of enhancement of chlorophyll accumulation by cytokinin pretreatment. Conversely, etiolated cotyledons that were equilibrated with 10-SM Ca 2+ in the presence of nifedipine, a blocker of some Ca 2+ channels, did not exhibit an enhancement of chlorophyll accumulation by cytokinin pretreatment, although they accumulated control levels of chlorophyll upon exposure to light and showed control levels of enhancement of chlorophyll accumulation by red-light pretreatment. These results indicate that external Ca 2+ is required for chlorophyll Abbreviations: A23187=antibiotic 23187 calcium ionophore; Chl = chlorophyll; nifedipine = 1,4-dihydro-2,6-dimethyl-4-(2'-nitrophenyl)-3,5-pyridinedicarboxylic acid dimethyl ester Correspondence to: C. Reiss; FAX: 1 (607) 255 5407; E-mail: hcrl@cornell.edu accumulation by excised etiolated cucumber cotyledons during the first 2 h of light exposure, and that an influx of external Ca 2 + is required for the enhancing effect of redlight and cytokinin. The differential abilities of Nd 3 § and nifedipine to block the effects of red-light and cytokinin pretreatments suggests that enhancement of chlorophyll accumulation by red-light and cytokinin may involve different classes of Ca 2 § channels.

Leaf lifetime photosynthetic rate and leaf demography in whole plants of Ipomoea pes-caprae growing with a low supply of calcium, a ‘non-mobile’ nutrient

“…Chl (a+b) content per unit of mass was 20% lower in low-Ca plants compared with control. This agrees with the fact that low Ca in the external solution decreases chlorophyll accumulation (Swamy and Suguma, 1992; Ramalho et al , 1995; Reiss and Beale, 1995; Milivojevic and Stojanovic, 2003) and causes damage of chloroplast lamellae (Repka et al , 1971). However, the difference in Chl (a+b) content between treatments disappears when it is expressed per leaf area.…”

Calcium Variously Mediates the Effect of Cytokinin on Chlorophyll and LHCPII Accumulation During Greening in Barley Leaves and Cucumber Cotyledons

“…The data suggest that CKs affect greening via increased ALA synthesis (Lew and Tsuji, 1982;Lechowski and Białczyk, 1993;Reiss and Beale, 1995). The levels of the two ALA synthesis enzymes glutamyl t-RNA reductase and glutamate 1-semialdehyde aminotransferase were elevated in darkgrown kinetin-treated barley seedlings (Yaronskaya et al, 2006).…”

Screening of high biomass and phenolic producing clonal lines of spearmint in tissue culture usingpseudomonasand azetidine‐2 carboxylate.

“…Since chlorophyll was stimulated in response to both treatments, this suggested that cytokinin content via purine metabolism may also be efficiently produced, since it is also known that cytokmins can stimulate chlorophyll synthesis (Stoynova, et al, 1996). Cytokinin may stimulate chlorophyll biosynthesis by affecting the amount of mRNAs related chl a/2>-binding protein and the small subunit of ribulose-1,5 biphosphate carboxylase/oxygenase (Cotton et al, 1990;Mok and Mok, 1994;Reiss and Beale, 1995;1997;Rodoni, et al, 1998). Biomass, RA and total phenolic stimulation may indicate that NADPH2 and sugar phosphates were efficiently produced for overexpression of the phenylpropanoid pathway for the synthesis of free as well as condensed phenolics like lignin on the cell wall.…”