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1.
Dry lettuce (Lactuca sativa L.) seeds (achenes) contain -galactosidase (EC 3.2.122) at a level which is maintained in the imbibed dormant state in darkness. Both red light (R) and gibberellic acid promote an increase in enzyme activity several hours prior to the completion of germination. Germination and enzyme activity are not essentially linked, however, for the latter can increase while the former is inhibited. -Galactosidase activity increases within the cotyledons and the endosperm following R stimulation, but the axis is essential to perceive the stimulus and to promote and maintain the increase in enzyme activity. A diffusible factor (or factors) is produced by and-or released from irradiated axes, and it migrates to the cotyledons (and possibly endosperm) to promote the increase in -galactosidase activity. Gibberellic acid, particularly in the presence of benzyladenine, can replace the requirement for irradiated axes.Abbreviations GA3
gibberellic acid
- R
red light 相似文献
2.
Mobilization of the endosperm cell-wall reserves of Lactuca sativa L. cv. Grand Rapids requires endo--mannanase and -galactosidase activity. A third enzyme, -mannoside mannohydrolase (EC 3.2.1.25) is also involved. We have determined the optimum extraction and assay conditions for this enzyme, which is soluble only in high-salt (1 M NaCl) buffer. It is located exclusively within the cotyledons, in association with a cellulosic cell-wall fraction. Its substrates are the products of endosperm cell-wall mobilization, mannobiose and mannotriose, which diffuse to the cotyledons and are hydrolyzed extracellularly by the -mannoside mannohydrolase.Abbreviation PNPM
p-nitrophenyl--mannopyranoside
We dedicate this paper to the memory of our friend and colleague Dr. Jacob D. Duerksen 相似文献
3.
Abscisic acid is a hormonal stress signal that moves in the xylem from the root to the different parts of the shoot where it regulates transpirational water loss and leaf growth. The factors that modify the intensity of the ABA signal in the xylem are of particular interest because target cells recognize concentrations. ABA(xyl), will be decreased as radial water flow through the roots is increased, assuming that radial ABA transport occurs in the symplast only. Such dilutions of the plant hormone concentration can be compensated in different ways, which help to keep the ABA-concentrations in the xylem constant: (i) apoplastic bypass flows of ABA, (ii) ABA flows between the stem parenchyma and the xylem during transport and (iii) the action of beta-D-glucosidases that release free ABA from its conjugates to the root cortex and the leaf apoplast. The significance of reflection coefficients (sigma(ABA)), permeability coefficients of membranes (P(S)(ABA)) and apoplastic barriers for ABA is discussed. 相似文献
4.
Hayashi E You Y Lewis R Calderon MC Wan G Still DW 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2012,124(8):1487-1502
Fruits and vegetables are rich sources of antioxidants in human diets and their intake is associated with chronic disease
prevention. Lettuce (Lactuca sativa L.) is a common vegetable in diets worldwide, but its nutritional content is relatively low. To elucidate the genetic basis
of antioxidant content in lettuce, we measured the oxygen radical absorbance capacity (ORAC) and chlorophyll (Chl) content
as a proxy of β-carotene in an F8 recombinant inbred line (RIL) in multiple production cycles at two different production sites. Plants were phenotyped at
the open-leaf stage to measure genetic potential (GP) or at market maturity (MM) to measure the influence of head architecture
(‘head’ or ‘open’). Main effect quantitative trait loci (QTL) were identified at MM (three Chl and one ORAC QTL) and GP (two
ORAC QTL). No main effect QTL for Chl was detected at GP, but epistatic interaction was identified in one pair of marker intervals
for each trait at GP. Interactions with environment were also detected for both main and epistatic effects (two for main effect,
and one for epistatic effect). Main effect QTL for plant architecture and nutritional traits at MM colocated to a single genomic
region. Chlorophyll contents and ORAC values at MM were significantly higher and Chl a to Chl b ratios were lower in ‘open’ types compared to ‘head’ types. The nutritional traits assessed for GP showed a significant association
with plant architecture suggesting pleiotropic effects or closely linked genes. Taken together, the antioxidant and chlorophyll
content of lettuce is controlled by complex mechanisms and participating alleles change depending on growth stage and production
environment. 相似文献
5.
K. Wakabayashi K. Soga T. Hoson S. Kamisaka H. Yoshimura K. Shibata 《Plant Growth Regulation》2001,33(3):169-173
The effect of two -amino acids, 2-amino-3-cyclopropyl-butanoicacid (ACPBA) and 2-amino-5-chloro-4-pentenoic acid (ACPA) on the growth oflettuce (Lactuca sativa L.) roots was investigated. BothACPBA and ACPA at 10–4 significantly inhibitedgrowth of roots of light-grown seedlings, while they had no effect on hypocotylgrowth. The lengths of cortical cells in the mature region of roots that hadbeen exposed to either compound were significantly shorter than those ofcontrolroots. Treatment with ACPBA and ACPA significantly decreased the mechanicalextensibility of root cell walls prior to the start of inhibition of rootgrowth. On the other hand, these compounds did not decrease the osmoticconcentration of the cell sap in root tissues. These results suggest that ACPBAand ACPA inhibit the cell elongation process of lettuce roots by decreasing themechanical extensibility of cell walls. 相似文献
6.
GA3 and GA20 were quantified in leaf extracts from true-to-type and somaclonal variants (dwarf and giant) of Musa AAA cv. Grand nain by GC-MS-SIM after purification on reverse- and normal-phase HPLC and detection by ELISA with GA3 antibodies and by a dwarf rice bioassay. GA3 concentration in dwarf plants was 811 ng g–1 dry weight. For normal and giant plants, the endogeneous GA3 levels were respectively 3.6 and 4.6 times higher. The GA20 concentration in the giant plant was 68 ng g–1 of dry weight. This concentration was, respectively, 4.6 and 7.3 times higher than those of normal and dwarf plants. These results suggest that the somaclonal variations affecting banana plant height are associated with modifications in GA metabolism.Abbreviations HPLC
High Performance Liquid Chromatography
- GC-MS
Gas Chromatography-Mass Spectrometry
- SIM
Selected Ion Monitoring
- GA
Gibberellin
- BSA
Bovine Serum Albumin
- PB
Phosphate Buffer 相似文献
7.
Incidence of Fusarium wilt in Cucumis sativus L. is promoted by cinnamic acid, an autotoxin in root exudates 总被引:4,自引:1,他引:4
The effects of Fusarium oxysporum f. sp. cucumerinum, the pathogen causing Fusarium wilt in cucumber and cinnamic acid, a principal autotoxic component in the root exudates of cucumber (Cucumis sativus L.), on plant growth, Photosynthesis and incidence of Fusarium wilt in cucumber were studied in order to elucidate the interaction of autotoxins and soil-borne pathogens in the soil sickness. F. oxysporum. f. sp. cucumerinum (FO) and cinnamic acid (CA) at 0.1 or 0.25 mM significantly decreased net photosynthetic rate, stomatal conductance and the quantum yield of Photosystem II photochemistry (PSII), followed by a reduction of plant biomass production, but did not induce photoinhibition. Pretreatment with CA before inoculation with FO increased the effectiveness of FO, together with a slight photoinhibition. CA pretreatment significantly increased percentage of plants affected by Fusarium wilt, browning index of vascular bundle and Fusarium population in the nutrient solution. All these results indicate that CA enhanced Fusarium wilt by predisposing cucumber roots to infection by FO through a direct biochemical and physiological effect. It is likely that soil sickness results from an interaction of many factors.
Abbreviations: CA – cinnamic acid; CFU – colony forming units; Ci – intercellular CO2 concentration; FO –Fusarium oxysporum (Schlechtend.:Fr) f. sp. cucumerinum (Owen) Snyder & Hansen; Fv/Fm– maximal quantum efficiency of PS II; Fv/Fm– the efficiency of excitation capture by open PS II centers; Gs – stomatal conductance; NPQ – non-photochemical quenching coefficient; Pn – net photosynthetic rate; PS II – Photosystem II; PS II– the quantum yield of PS II photochemistry; qP – photochemical quenching coefficient. 相似文献
8.
9.
Terbium(3+) as a probe of nucleic acids structure. Does it alter the DNA conformation in solution? 总被引:1,自引:0,他引:1
At low ionic strength, Tb3+ binding strongly alters the secondary structure of DNA. Circular dichroism and electro-optical techniques are more sensitive than fluorescence to study these alterations in double-stranded DNA, at low Tb3+/DNA phosphate (I/P) ratios. Both techniques yield the following conclusion: as I/P is increased, native and sonicated DNA undergo a transition from the B- to psi-form, the latter being a compact structure characteristic of aggregated DNA. Our study of alkylated DNA establishes that the accessibility of N-7 guanine to Tb3+ is clearly required for structural alterations in an aggregated state to occur. The chelation of the phosphate group and of the N-7 guanine by Tb3+ simultaneously alters the geometry of the sugar-phosphate backbone and the stacking interaction between the bases in double-stranded DNA. 相似文献
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13.
The effect of root growth temperature on maximal photosynthetic CO2 assimilation (P
max), carbohydrate content, 14C-photoassimilate partitioning, growth, and root morphology of lettuce was studied after transfer of the root system from
cool root-zone temperature (C-RZT) of 20 °C to hot ambient-RZT (A-RZT) and vice versa. Four days after RZT transfer, P
max and leaf total soluble sugar content were highest and lowest, respectively, in C-RZT and A-RZT plants. P
max and total leaf soluble sugar content were much lower in plants transferred from C-to A-RZT (C→A-RZT) than in C-RZT plants.
However, these two parameters were much higher in plants transferred from A-to C-RZT (A→C-RZT) than in A-RZT plants. A-RZT
and C→A-RZT plants had higher root total soluble sugar content than A→C-RZT and C-RZT plants. Leaf total insoluble sugar content
was similar in leaves of all plants while it was the highest in the roots of C-RZT plants. Developing leaves of C-RZT plants
had higher 14C-photoassimilate content than A-RZT plants. The A→C-RZT plants also had higher 14C-photoassimilate content in their developing leaves than A-RZT plants. However, more 14C-photoassimilates were translocated to the roots of A-RZT and C→A-RZT plants, but they were mainly used for root thickening
than for its elongation. Increases in leaf area, shoot and root fresh mass were slower in C→A-RZT than in C-RZT plants. Conversely,
A→C-RZT plants had higher increases in these parameters than A-RZT plants. Lower root/shoot ratio (R/S) in C-RZT than in A-RZT
plants confirmed that more photoassimilates were channelled to the shoots than to the roots of C-RZT plants. Roots of C-RZT
plants had greater total length with a greater number of tips and surface area, and smaller average diameter as compared to
A-RZT plants. In C→A-RZT plants, there was root thickening but the increases in its length, tip number and surface area decreased.
The reverse was observed for A→C-RZT plants. These results further supported the idea that newly fixed photoassimilates contributed
more to root thickening than to root elongation in A-RZT and C→A-RZT plants. 相似文献
14.
In order to explain the mechanisms of Calvin-cycle regulation, the general properties of metabolic systems under homeostatic flux control are analyzed. It is shown that the main characteristic point for an enzyme in such a system can be the value of a sharp transition from some constant homeostatic flux to a limitation by this enzyme. A special method for the quantitative treatment of the experimental dependence of a metabolic flux such as photosynthesis on enzyme content is developed. It is pointed out that reactions close to a thermodynamic equilibrium under normal conditions can considerably limit the homeostatic fluxes with a decrease of the enzyme content. Calvin-cycle enzymes are classified as non-limiting, near-limiting and limiting. The deduced rules for the regulation of a homeostatic metabolic pathway are used to explain the data obtained for transgenic plants with reduced activities of Calvin-cycle enzymes. The role of compensating mechanisms that maintain the photosynthesis rate constant upon the changes of enzyme contents is analyzed for the Calvin cycle. The developed analysis explains the sharp transitions between limiting and non-limiting conditions that can be seen in transgenic plants with reduced content of some Calvin-cycle enzymes, and the limiting role of such reversible enzymes as aldolase, transketolase and others. The attempt is made to predict the properties of plants with increased enzyme contents in the Calvin cycle. 相似文献
15.
This study examined the role of endogenous abscisic acid (ABA) and jasmonic acid (JA) in indirect somatic embryogenesis of
Medicago sativa L. A multiplex GC-MS/MS technique allowed quantitative single-run analyses of ABA, JA, 12-oxophytodienoic acid (OPDA) and
indole-3-acetic acid (IAA). The preparation of initial explants led to a strong accumulation of ABA, JA and OPDA but not of
IAA. Substantially higher levels of ABA, JA and OPDA were detected in developing somatic embryos than in callus or embryogenic
suspension. Fluridone (FLD) decreased ABA, JA and OPDA levels. Indoprofen (INP) appeared to be a specific inhibitor of octadecanoid
biosynthesis. Somatic embryo production and development were negatively affected by FLD or INP. Only INP (0.5 μM) applied
during proliferation phase increased the number of cotyledonary embryos. The results strongly indicate the involvement of
ABA and JA in somatic embryogenesis of M. sativa. Surprisingly, low IAA contents in comparison to stress-related compounds (ABA, JA and OPDA) were detected in explants, embryogenic
tissues and somatic embryos. 相似文献
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Iqbal Hussain Asif Siddique Muhammad Arslan Ashraf Rizwan Rasheed Muhammad Ibrahim Muhammad Iqbal Sobia Akbar Muhammad Imran 《Acta Physiologiae Plantarum》2017,39(6):144
Seed priming increases tolerance of plants against various environmental stresses. Although ample literature is available that depicts the beneficial effects of priming under different environmental stresses, the information on induction of tolerance to Pb stress through seed priming with ascorbic acid (AsA) is limited. Therefore, this study was performed to examine the effect of seed priming with AsA (50 and 100 mg L?1), hydropriming and without priming (control) on physiochemical processes of okra cultivars (Subz-Pari and Arka Anamika) under Pb stress (0, 100 mg L?1). Pb stress caused a considerable decline in plant growth and photosynthetic pigments. Contrarily, Pb stress exhibited rise in the contents of total amino acids, free proline, total soluble proteins and AsA. The POD, CAT, and SOD activities were recorded highest at 100 mg L?1 of Pb. Moreover, Pb stress markedly increased H2O2 and MDA levels that triggered oxidative stress. However, plants raised from seed primed with AsA and water exhibited better growth and had higher chlorophylls, free proline, total proteins, total amino acids, AsA and activities of enzymatic antioxidants. Priming with AsA (50 mg L?1) induced better tolerance to Pb stress in okra plants. Plants of cv. Arka Anamika exhibited greater tolerance to Pb than that of cv. Subz-Pari as was evident from higher plant fresh and dry masses. 相似文献