摘要:

Somatic embryos were observed as early as six days after subculturing immature embryos ofTriticum aestivumL. (cvs Froid‐Centurk and Helge) in vitro on 2,4‐dichloro‐phenoxyacetate‐containing nutrient media. Embryo formation followed three pathways, each involving one of the scutellum's three basic tissue systems: dermal, ground and vascular.(1) Single epithelial layer cells divided tangentially to give pseudothallus‐like structures which, through radial and oblique divisions, assumed polar, proembryoid symmetry.(2) In actively dividing ground tissues, localized asymmetrical division in some cells resulted in proembryoids. When contiguous with each other, the proembryoids could be identified as a proembryonic mass.(3) Oblique divisions in some cells of the scutellum's procambium resulted in daughter cells of unequal size, from the smaller of which the embryoid's root would eventu

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb01893.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Development and acclimation of energy transduction were studied in seedlings ofChenopodium rubrumL. ecotype selection 184 (50° 10′ N; 105° 35′ W) in response to photomorphogenic and photoperiodic treatments. Dark respiration and photosynthetic capacity [nmol O2(pair of cotyledons)−1h−1] were measured with an oxygen electrode. Changes in chloroplast ultrastructure were analyzed concomitantly. After germination, seedlings were grown at constant temperature either in darkness or in continuous light (white, red, far‐red and blue) or were subjected to diurnal cycles of light/dark or changes in light quality. Dark respiration was low in far‐red light treated seedlings. In red light treated seedlings dark respiration was high and the mean value did not depend on fluence rate or photoperiod. Blue light stimulated transitorily and modulated dark respiration in photoperiodic cycles. Photosynthetic capacity was reduced by far‐red light and increased by red light. In response to blue light photosynthetic capacity increased, with indications of a requirement for continuous energy input. Phytochrome and a separate blue light receptor seemed to be involved. In continuous red light a clear cut circadian rhythm of dark respiration was observed. Blue light had a specific effect on chloro

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb01894.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

When adding aluminium (3.7–370 μM) as AlCl3–6H20 to cultures of the nitrogen‐fixing cyanobacteriumAnabaena cylindrica, strain 1403/2a (CCAP), the following responses were observed: The effects of aluminium were dependent on pH. being most drastic at pH 6.0. At this pH the growth ofA. cylindricawas significantly reduced by 3.7 μMaluminium and completely inhibited by 370 μM. The content of chlorophyll a and phycocyanin decreased after treatment with aluminium. Also, aluminium lowered the rates of both CO2‐fixation and N2‐fixation with total inhibition of both processes by 370 μM. At the lower concentrations used the nitrogenase activity started to recover after about 100 h. The aluminium content in the cells increased with increasing concentration and with time. At 190 μMthe aluminium concentration in the cells represented 2.4 and 3.3% of the dry weight after 6 and 24 h, respectively. Clogging of filaments and lysis of vegetative cells were apparent at higher aluminium concentrations while the frequency of heterocysts increased in all concentrations used. The most pronounced ultrastructural changes included accumulation of cyanophycin granules and degradation of the thylakoids. The ultrastructure of the heterocysts was however not affected. It is concluded that major reasons for the toxicity are interactions with membranes and phosph

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb01895.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Three inbred lines of maize (Zea maysL.) from cool temperate regions and three from warm regions were grown at 14, 22, 30 and 38°C up to the same physiological age, the full expansion of the third leaf. The laminae of the second leaf were studied for anatomical traits of the chlorenchyma. The genotypic variation was considerable for all properties. Nevertheless, general temperature response curves existed for many properties with few deviations of single lines. The cross‐sectional area of mesophyll cells and cross‐sectional area and number of chloroplasts declined from 14 to 22°C, increased up to 30°C and declined again up to 38°C. The ratio of shortest to longest diameter of chloroplasts was low in mesophyll cells at intermediate temperatures, and maximum in bundle sheath cells at 30°C. Temperature response curves for other properties of the bundle sheath cells were predominantly genotype specific. Chloroplasts in bundle sheath cells were sometimes smaller than those of mesophyll cells, dependent on temperature and genotype. Values of lines from cool temperate and warm regions were mostly overlapping, but the cross‐sectional area of mesophyll cells was larger in the latter than in the former lines at low temperature. The results are discussed in relation to the expression of photosynthetic

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb01896.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

‘York Imperial’ apple seedlings (Malus domesticaBorkh.) were continuously supplied via the roots with paclobutrazol [(2RS, 3RS)‐1‐(4‐chlorophenyl)‐4,4‐dimethyl‐2‐(1,2,4‐triazol‐1‐yl)pentan‐3‐ol)], a triazole GA biosynthesis inhibitor, at 0.68 μMin a nutrient solution. In comparison to controls, seedlings treated with paclobutrazol for 66 days showed a 91% reduction in shoot length, a 66% reduction in leaf area but only a 17% reduction in leaf number. This effect could be reversed by GA3applied to the foliage at 71.4 μM0, 19 or 35 days after paclobutrazol was initially supplied and leaf area values for paclobutrazol‐treated seedlings given both treatments did not differ significantly from controls. Plots of growth data indicate linearity of shoot longitudinal growth of GA3‐treated seedlings. Leaf area increase was non‐linear after GA3treatment up to approximately 30 days, when the rate dropped. On a per shoot basis, leaf weight closely followed leaf area but on a per unit area basis, paclobutrazol‐treated leaves were heavier than controls; GA3applica

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb01897.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Some physiological and biochemical changes in apple seedlings (Malus domesticaBorkh cv. ‘York Imperial’) caused by an inhibitor of gibberellin biosynthesis, paclobutrazol [(2RS, 3RS)‐1‐(4‐chlorophenyl)‐4,4‐dimethyl‐2‐(1,2,4‐triazol‐1‐yl) pentan‐3‐ol], were determined. Paclobutrazol shifted assimilate partitioning from leaves to roots, increased carbohydrates in all parts of apple seedlings, increased chlorophyll content on a leaf area basis, increased soluble protein in leaves, increased mineral element concentration in leaf tissue and increased root respiration. Foliar application of gibberellic acid (GA3) counteracted the effec

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb01898.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Young sunflower plants (Helianthus annuusL. cv. Halcón), grown in nutrient solution at two K+levels (0.25 and 2.5 mM) were used to study the effect of K+content in the root on uptake and transport of K+to the exuding stream of decapitated plants. Roots of plants grown in low K+gave higher exudation flux, higher K+concentration in exudate and higher K+flux than high K+roots. After 6 h of uptake the K+flux in low K+roots was about three times that in high K+roots. When the roots were kept in a nutrient solution in which Rb+replaced K+, low K+roots exuded much more Rb+than K+after the first 2 h, whereas high K+roots exuded about similar amounts of K+and Rb+. In intact plants grown at three different K+levels (0.1, 1.0 and 10.0 mM), there was an inverse relationship between the K+level in the nutrient solution and the Rb+accumulated in the roots or transported to the shoot. The results suggest that the transport of ions from xylem parenchyma to stele apoplast may be controlled by ions coming down from the shoot in sieve tubes

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb01899.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Steady state kinetics were used to examine the influence of Cd2+both on K+stimulation of a membrane‐bound ATPase from sugar beet roots (Beta vulgarisL. cv. Monohill) and on K+(86Rb+) uptake in intact or excised beet roots. The in vitro effect of Cd2+was studied both on a 12000–25000 g root fraction of the (Na++K++Mg2+)ATPase and on the ATPase when further purified by an aqueous polymer two‐phase system. The observed data can be summarized as follows: 1) Cd2+at high concentrations (>100 μM) inhibits the MgATPase activity in a competitive way, probably by forming a complex with ATP. 2) Cd2+at concentrations<100 μMinhibits the specific K+activation at both high and low affinity sites for K+. The inhibition pattern appears to be the same in the two ATPase preparations of different purity. In the presence of the substrate MgATP, and at K+10 μM, the inhibition by Cd2+is competitive. 3) At the low concentrations of K+, Cd2+also inhibits the 2,4‐dinitrophenol(DNP)‐sensitive (metabolic) K+(86Rb+) uptake uncompetitively both in excised roots and in roots of intact plants. 4) The DNP‐insensitive (non metabolic) K+(86Rb+) uptake is little influenced by Cd2+. As Cd2+inhibits the metabolic uptake of K+(86Rb+) and the K+activation of the ATPase in the same way at low concentrations of K+, the same binding site is probably involved. Therefore, under field conditions, when the concentration of K+is low, the presence of Cd2+could be d

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb01900.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The oxidation of exogenous NADH by mitochondria from potato (Solanum tuberosumL., cv. Bintje) tubers, measured with different electron acceptors, oxygen, cytochromec, duroquinone and ubiquinone 1, was greatly enhanced under high salt conditions compared to low salt conditions, confirming the stimulatory effect of electrostatic screeening of negative membrane charges by cations. In addition to this nonspecific stimulation, the oxidation of exogenous NADH showed a specific dependence on Ca2+. Results presented here suggest that calmodulin was not directly involved in the regulation of exogenous NADH oxidation by potato mitochondria: (1) Calmodulin antagonists were found to inhibit electron flow at several sites in a nonspecific manner. (2) Using a phenothiazine‐Affi Gel column, it was not possible to demonstrate the presence of calmodulin in Triton X‐100 solubilized mitochondria. (3) Fractions eluted from a calmodulin‐Sepharose column with EGTA [ethyleneglycolbis (β‐aminoethylether)‐N, N, N′, N′‐tetraacetic acid] did not display any activity related to mitochondrial electron transport, suggesting that NADH dehydrogenase had no specific affinity for calmodulin. The possible indirect involvement of calmodulin in the regulation of exogenous NADH oxidation by

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb01901.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Photosynthetic CO2‐fixation of mesophyll protoplasts of lambs lettuce [Valerianella locusta(L.) Betcke] was inhibited by short time exposure to Cd+. Inhibition was due to uptake of the metal ion into the protoplasts and increased with increasing Cd2+concentrations and the time of preincubation. A 10 min pretreatment at 2 mMCd2+reduced CO2‐fixation by 40–60%. Inhibition of photosynthesis was independent of the light intensity to which the protoplasts were exposed. Measurement of the lightinduced electrochromic pigment absorption change at 518nm and chlorophyll fluorescence studies revealed that primary photochemical reactions associated with the thylakoid membranes were not affected by the metal ion. Also, light activation of the ribulose‐1,5‐bisphosphate carboxylase (EC 4.1.1.39) was not inhibited by Cd2+. Under rate‐limiting CO2concentrations, inhibition of CO2‐fixation was smaller than at Vmaxof CO2reduction indicating that the carboxylation reaction of the Calvin cycle is not susceptible to Cd2+. Cd2+treatment of protoplasts significantly extended the lagphase of CO2‐supported O2‐evolution and partly inhibited light activation of the glyceraldehyde‐3‐phosphate dehydrogenase (EC 1.2.1.13) and the ribulose‐5‐phosphate kinase (EC 2.7.1.19). Measurement of relative concentrations of [14C]‐labeled Calvin cycle intermediates showed that Cd2+caused a decrease in the 3‐phosphoglycerate/triose phosphate ratio and an increase in the triose phosphate/ribulose‐1,5‐bisphosphate ratio. It is concluded that in protoplasts Cd2+affects photosynthesis mainly at the level of dark reactions and that the site of inhibition may be localized in the regen

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb01902.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY