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Effect of humic substances on nitrogen uptake and assimilation in two species of pinus
No full textThe aim of this paper was to test the effect of forestry humic substances on nitogen uptake and on the activity of key enzymes of nitrogen assimilation in two differen species of pinus
The effects of humic substances on pinus callus are reversed by 2,4-Dichlorophenoxy acetic acid
No full textThe reversal of humic matter-induced inhibition of callus growth
and metabolism by 2,4-dichlorophenoxyacetic acid (2,4-D) was studied in
Pinus laricio. Two forest humic fractions (relative molecular mass (Mr) >
3500), derived from soil under Fagus sylvatica (Fs) and Abies alba (Aa) plantation,
were used. Pinus laricio calluswas grown for a subculture period (4 weeks)
on Basal Murashige and Skoog (MS) medium plus forest humic matters (Fs or
Aa), at a concentration of 1 mg C/l, and then was transferred, for an additional
four weeks, to a MS medium culture without humic matter, but with different
hormones: indole-3-acetic acid (IAA, 2 mg/1) or 2,4-dichlorophenoxyacetic
acid (2,4-D, 0.5 mg/1) and/or 6-benzylaminopurine (BAP, 0.25 mg/1). Growth
of calluse, glucose, fructose, and sucrose contents, and activities of soluble
and bound invertases, glucokinase, phosphoglucose isomerase, aldolase, and
pyruvate kinase were monitored. The results show a negative effect of humic
fractions on callus growth, due to decreased utilization of glucose and fructose,
and decreased activities of glycolytic enzymes. The effects are reversible.
Substitution of humic fractions with 2,4-D+BAP or 2,4-D is followed by an
increase of glycolytic enzyme activities and, consequently, by the utilization of
glucose and fructose that induces a restart of growth. In contrast, the inhibitory
effects of humic fractions persist when they are substituted with BAP alone,
indicating that only the auxin 2,4-D is capable of reversing the negative effects.
A possible competitive action on the auxin-binding site between 2,4-D and the
chemical structures in the forest humic fractions is suggested
AUXIN-LIKE EFFECT OF HUMIC SUBSTANCES EXTRACTED FROM FECES OF ALLOLOBOPHORA-CALIGINOSA AND ANTENNARIA-ROSEA
No full textLeaf explants of Nicotianaplumbaginifolia were compared in cultures supplemented with IAA,
inhibitors of IAA (TIBA = 2,3,Qriiodobenzoic acid and PCIB = 4-chlorophenoxy-isobutyric acid) and
a humic substance (HEf) obtained from the faeces of Allolobophora caliginosa and A. rosea. The results
show that HEf at a concentration of 1 mg Cl- ’ causes root development from leaf explants that appears
to be similar to MA-induced activity, while the control did not develop roots. Furthermore HEf induced
longer roots than those grown in IAA with fewer hair roots. In the presence of the IAA inhibitors, the
leaf explants were without roots. Humic matter, IAA and IAA-inhibitors stimulated peroxidase activity
in N. plumbaginifolia. Also, when the Nicotiana tissues were treated with the humic fraction and IAA there
was a minor polymorphism in the esterase isoenzymes. The presence of both TIBA and PCIB restored
the esterase profile obtained from control tissues. The induced root-forming activity in leaf explants and
the minor polymorphism with respect to the control in the esterase zymograms demonstrate that the humic
substance exhibited auxin-like activity.
HEf, a low molecular size fraction, was obtained from the faeces of Ailolobophora caliginosa (Sav.) and
A. rosea (Sav.) by disaggregating the humic material with acetic acid, confirmed the effectiveness of the
combination of high acidity and low molecular size in influencing the biological activity of the plant system
tested
Effetto della fosfinotricina sul grano duro (Triticum durum Desf., cv. Simeto): interazione con la glutammina sintetasi.
No full textCaratteristiche cinetiche della inibizione da fosfinotricina della glutammina sintetasi GS2 di grano duro (Triticum durum Desf., cv. Simeto). Atti del XI Congresso della Soc. Ital. di Chimica Agraria pp.
No full textThe ascorbate system during the early stage of germination in Pinus laricio seeds treated with extracts from two different sources of humus
No full textThe aims of the paper was to study how the AA biosynthetic capacity, as well as the activities of REDOX enzymes of the ascorbate systems during the early stage of pinus laricio germination, were affected by humus from two forestry sites
Effect of molecular complexity and acidity of earthworm faeces humic fractions on glutamate dehydrogenase, glutamine synthetase, and phosphoenolpyruvate carboxylase in Daucus carota alpha II cells
No full textCarrot cells were grown in cultures supplemented with two hormones [2,4-dichlorophenoxyacetic acid (2,4-D) and 6-benzylaminopurine (6BAP)] and two humic fractions extracted from earthworm faeces, one with high acidity and a low apparent molecular size (<3500) and the other with low acidity and a large molecular size. 2,4-D stimulated growth through an effect on eel enlargement, while the strongly acidic humic fraction (0.2 mg l(-1)) and the weakly acidic fraction (1 mg l(-1)) were both less effective. With 4-16 h of pre-incubation, the highly acid humic fraction, mainly alone, induced the best increase in protein content; the effect of the weakly acid humic fraction and the hormones was generally less important. The two humic fractions also differed in their influence on glutamate dehydrogenase activity. After 2 h of pretreatment, the highly acidic fraction increased glutamate dehydrogenase activity, while the other fraction did not affect it. After 4-16 h of pre-incubation, the activity of this enzyme was still not influenced by these humic fractions. The presence of the two hormones did not interfere with the humic matter effects. Glutamine synthetase activity was not affected by a pre-incubation of up to 4 h with the two humic fractions, but it was stimulated after 8-16 h of pre-incubation. A 2,4-D+6BAP mixture stimulated glutamine synthetase activity (from +12 to +50%). Again, the presence of the hormones did not interfere with the effects induced by the humic fractions. After 16 h of pre-incubation, phosphoenolpyruvate carboxylase activity was increased by the highly acidic humic fraction (+93%) and by both humic fractions together (+34%). An explanation of the different incubation times necessary for the humic fractions to exert stimulatory effects on these enzymes is proposed here. The regulatory properties of the strongly acidic humic fraction appeared to depend on the combination of high acidity (expecially carboxylic C) with low molecular size
Alteration of aminoacid metabolism by humic substances during germination of Pinus laricio seeds
No full textThe results suggest that HS inhibit seed germination by affecting metabolic processes, in particular the krebses cycle that provides the carbon skeleton necessary to synthesize aminoacids
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