T. V. R. Nair

Nitrate reductase activity in developing wheat ears

Die Fruchtstände der Weizenpflanzen reduzieren während ihrer Entwicklung beachtliche Mengen von Nitratstickstoff.

Impact of Arbuscular-Mycorrhizal Fungi on Phosphorus Efficiency of Wheat, Rye, and Triticale

ABSTRACT Genotypic variation and mycorrhiza play an important role in plant uptake of phosphorus (P). A pot experiment was conducted with three cereals, wheat (Triticum aestivum L. cv. PBW-34), rye (Secale cereale L. cv. R-308), and triticale (Triticale octoploide L. cv. DT-46), a hybrid of wheat and rye, to examine the genetic variation in the degree of arbuscular-mycorrhizal (AM) infection and its inheritability from parents (wheat and rye) to their progeny (triticale). The soil used for pot culture was low in available P (7.8 mg P kg−1soil). Inoculation with AM fungi showed a significant increase in extent of root colonization for all three cereals (average 70%) compared with their performance without AM (average 19.1%). However, among the three cereals, this increase was significantly greater in rye than in the other two crops, while wheat and triticale did not differ significantly. Mycorrhizal infection resulted in 1.6, 1.7, and 1.8-fold increases in shoot, root, and total plant dry matter, respectively, compared with the un-inoculated treatment. Among the three cereals, rye recorded maximum shoot, root, and total plant dry mass and P content with AM inoculation. The P uptake by wheat, rye, and triticale was 10%, 64%, and 35%, respectively, higher with rather than without mycorrhizal infection. Rye was most responsive to AM inoculation, with mycorrhizal dependency of 193%; here again, triticale followed wheat, with similar mycorrhizal dependency. Rye showed an increase in P utilization efficiency (PUE) without AM inoculation while the PUE of triticale was intermediate between wheat and rye. High efficiency of AM symbiosis in terms of P uptake exists in rye and most of these traits in triticale seem to be inherited from wheat rather than rye.

Effect of photorespiratory metabolites, inhibitors and methionine sulphoximine on the accumulation of ammonia in the leaves of mung bean and Amaranthus

Abstract The free ammonia (NH3) level, and its accumulation in the presence of methionine sulphoximine (MSO) were investigated in the leaves of a C3 (Vigna radiata) and a C4 (Amaranthus edulis) plant, both in the presence and absence of photorespiratory inhibitors, isonicotinyl hydrazide (INH) or α-hydroxypyridine methane sulphonate (α-HPMS) as well as when fed with photorespiratory intermediates, glycolate or glycine. The endogenous level of free NH3 was slightly greater in the C4 than in the C3 plant in control treatments but when NH3 assimilation was blocked with MSO, the difference was reversed. The inhibition of MSO-induced accumulation of NH3 by INH and α-HPMS was four times more effective in Vigna (C3) than in Amaranthus (C4). Glycine feeding enhanced the NH3 accumulation with MSO and the enhancement was similar in both C3 and C4 plants. However, NH3 accumulation with MSO and glycolate feeding was more in the C3 than in the C4 plant. The increase in MSO-induced NH3 accumulation on glycine or glycolate feeding were inhibited ny INH or α-HPMS, respectively.

Carbon dioxide assimilation in urea-treated wheat leaves

Abstract Application of 10 mM urea to the flag leaf of wheat plants enhanced in vivo urease activity several fold. Photosynthetic rate was also increased considerably. There were significant differences in the leaf internal carbon dioxide (CO2) concentrations between the urea‐treated and untreated leaves. The finding that carbon (14C) was detected in the ethanol extract of the leaves fed with 14C‐urea suggests that CO2 released from urea is re‐fixed by the leaves.

Effect of exogenous supply of amino acids, amide, urea and ureide on free NH4+ level in mung beans

The results of experiments on the possible source(s) of ammonia for the mung bean are reported. Different nitrogenous metabolites were fed to primary leaves of mung bean seedlings with and without methionine sulphoximine (MSO), an inhibitor of glutamine synthetase (GS). Their role in foliar ammonia loss is discussed.