Plastochrone, cycle cellulaire et teneurs en ADN nucléaire du méristème caulinaire de plants de Chrysanthemum segetum soumis à deux conditions lumineuses différentes, sous une photopériode de 16 heures

Abstract

Plastochrone, cycle cellulaire et teneurs en ADN nucleaire du meristeme caulinaire de plants de Chrysanthemum segetum soumis a deux conditions lumineuses differentes, sous une photoperiode de 16 heures R e~u le 1" dtcembre 1989 NOUGAREDE, A,, DI MICHELE, M. N., RONDET, P., et SAINT-COME, R. 1990. Plastochrone, cycle cellulaire et teneurs en ADN nuclCaire du meristbme caulinaire de plants de Chrysanthemum segetum soumis a deux conditions lumineuses differentes, sous une photoperiode de 16 heures. Can. J. Eot. 68: 2389-2397. Des plants de Chrysanthemum segetum sont cultivCs en photopCriode de 16 h sous deux Cclairements diffkrents (70 ou 200 pmol m-2 s-I).Sous 200 pmol m -2 s -I, par comparaison B 70 pmol m-2 s-I, la phyllotaxie n'est pas modifiCe, mais le plastochrone dCcroit et le diambtre apical s'accroit par extension de la zone axiale. Le temps moyen de doublement cellulaire decroit de 36,2% en zone laterale, de 29% en zone axiale et de 13% seulement dans le mCristbme mCdullaire. La durCe de la mitose reste, par contre, constante. Sous les deux conditions lumineuses, les noyaux, dont les teneurs en ADN sont localisCes dans les limites de la repartition 2C, sont predominants, ce qui signifie que la phase G , du cycle cellulaire est la plus longue. Sous 200 pmol m-2 s -' , le raccourcissement du temps moyen de doublement cellulaire va de pair avec une rkduction du pourcentage des noyaux compris B I'intCrieur des limites de la repartition 2C; la reduction de ce pourcentage est la plus importante dans la zone latCrale et la moins importante dans le mCristbme medullaire, montrant qu'un contr6le de la prolifkration s'exerce par l'intermkdiaire de la phase G I du cycle cellulaire.Mots clPs : Chrysanthemum segetum, cycle cellulaire, duke de la mitose, plastochron:, teneurs en ADN nuclCaire, zonation. NOUGAREDE, A., DI MICHELE, M. N., RONDET, P., and SAINT-COME, R. 1990. Plastochrone, cycle cellulaire et teneurs en ADN nuclCaire du mtristbme caulinaire de plants de Chrysanthemum segetum soumis B deux conditions lumineuses diffkrentes, sous une photopCriode de 16 heures. Can. J. Bot. 68 : 2389-2397. Chrysanthemum segetum plants were grown from seeds under a 16-h photoperiod, at two different photon fluence rates (70 or 200 pmol m-2 s-I. At 200 pmol m-' s-', by comparison with 70 pmol m-2 s-I, phyllotaxy was not modified, but the plastochron decreased and the apical diameter increased by extension of the axial zone. The mean cell doubling time decreased 36.2% in the lateral zone, 29% in the axial zone, and only 13% in the rib meristem. In contrast, mitosis duration was constant. Under both light conditions, nuclei with a DNA content within the limits of the 2C range were always predominant, which means that the GI phase of the cell cycle was the longest. At 200 pmol m-2 sC1, the shortening of the mean cell doubling time is accompan~ed by a reduction of the percentage of nuclei with DNA levels within the limits of the 2C range. The decrease of the latter was the most important in the axial zone and the least important in ...

Sugar Control of the Plant Cell Cycle: Differential Regulation ofArabidopsisD-Type Cyclin Gene Expression

“…At elevated CO 2 concentrations, a more rapid progression through the cell cycle is due to an increase in the number of rapidly cycling cells in the apical meristem and to a reduction in cell cycle length (23,26). More rapid cell divisions due to a shorter G 1 phase were observed when Chrysanthemum plants were exposed to increase light levels (42). Both high light and elevated CO 2 levels are likely to increase the photosynthetic yield and sugar levels.…”

“…Many plant cells arrest in G 1 in response to nutrient limitation or differentiation (12). G 1 is also the major extendable part of the cell cycle in response to alterations in conditions such as temperature (14), CO 2 levels (26), and light levels (42), and it might be expected that a primary control of cell cycle entry will therefore be imposed during the G 1 phase (41).…”

Phyllochron duration and changes through rice development shape the vertical leaf size profile

“…Similar negative correlations have been noted between the rate of leaf appearance and either the size of leaf 7 in 190 rice varieties (Rebolledo et al ., 2012) or the sizes of leaves 1 and 2 in two sets of 28 and 50 wheat varieties (Rebetzke & Richards, 1999). Finally, in chrysanthemum and rice, shorter plastochrons are correlated with a greater rate of cell division in the apical meristem and larger apical meristem sizes (Nougarède et al ., 1990; Itoh et al ., 1998). In chrysanthemum, the duration of cell number doubling was shorter, although the duration of mitosis itself did not vary.…”

Le méristème caulinaire des Angiospermes: nouveaux outils, nouvelles interprétations

“…'interphase, dont G 1 , peuvent participer a l'allongement du cycle en zone axiale. e-chez Chrysanthemum segetum (Nougarede eta!., 1990) Rembur, 1972Rembur, , 1978Phytolacca decandra, Nougarede et a/., 1973 ;Bryophyllum daigremontianum, Brossard, 1973 ;Nicotiana tabacum, Brossard, 1975 ; Pisum sativum, Lyndon, 1973Lyndon, , 1976Nougarede & Rondet, 1975a et b ;Toupiol, 1976 ;Fraxinus excelsior, Cottignies, 1974, 1983Nougarede et a/., 1996 Lyndon, 1973Lyndon, , 1976Lyndon, , 1990. Table 18.-Mean duration in hours of the cell cycle and of its phases in the Pisum sativum (Lincoln) vegetative shoot apical meristem.…”

“…'apparition des sepales (Taylor eta/., 1990). Correlativement, Ia zonation, les dimensions apicales et les index mitotiques sont modifies (Nougarede et a/., 1991 ). C'est aussi durant l'etape preflorale que Ia duree du cycle cellulaire se raccourcit considerablement et, specifiquement, dans l'ancienne zone axiale (Nougan':de et a/., 1987).…”