Browsing by Author "J.K. Ladha"

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Effects of some amino acid analogues on growth and heterocyst formation in the blue-green alga Nostoc linckia
(1978) J.K. Ladha; H.D. Kumar
The effects of two amino acid analogues, viz., L-methionine-DL-sulphoximine and L-methyl-DL-methionine on growth, heterocyst differentiation and nitrogen fixation in the blue-green alga Nostoc linckia have been studied with special reference to heterocyst spacing pattern. L-methionine-DL-sulphoximine strongly inhibited growth but produced an unusual number of heterocysts with changed heterocyst spacing pattern in both nitrogen-free and ammonium-containing media. L-methyl-DL-methionine was less effective than L-methionine-DL-sulphoximine. An attempt was also made to counteract the toxic effects of these analogues by supplying amino acids. Glutamine and methionine reversed the inhibitory effect of L-methionine-DL-sulphoximine while only methionine reversed the inhibitory effect of L-methyl-DL-methionine. Production of changed heterocyst spacing pattern in nitrogen-free and ammonium-containing media when supplemented with L-methionine-DL-sulphioximine suggests that ammonia may not be the inhibitor of heterocyst spacing pattern. © 1978 Indian Academy of Sciences.
Genetic control of heterocyst formation in the blue-Green algae Nostoc muscorum and nostoc linckia
(Springer-Verlag, 1977) H.N. singh; J.K. Ladha; H.D. Kumar
Non-heterocystous, non-nitrogenfixing (het- nif-), heterocystous, non-nitrogenfixing (het+ nif-) and multiple heterocystous, nitrogen-fixing (M-het+ nif+) mutants of heterocystous, nitrogen-fixing (het+ nif+) wild-type Nostoc muscorum and Nostoc linckia were isolated and characterized with respect to (a) nitrogenfixing activity, (b) reversion frequency, (c) ammonium repressibility of heterocyst formation, (d) heterocyst spacing pattern, and (e) action of L-methionine-DL-sulphoximine (MSO), an inhibitor of glutamine synthetase (GS), on heterocyst regulation. The mutant and revertant results suggest: (i) either involvement of a common genetic determinant in the formation of heterocyst and nitrogenase or the organization of het genes and nif genes in a single operon prone to complete inactivation by a single polar mutation, (ii) non-participation of active nitrogenase in regulation of heterocyst spacing; (iii) involvement of genetic factor(s) in the control of heterocyst spacing pattern in N. linckia, and (iv) apparently different nature of the mechanism of heterocyst inhibition by proheterocyst from that of heterocyst inhibition by NO3-or NH4+. L-Methionine-DL-sulphoximine inhibits growth and causes heterocyst formation in chains in N. linckia growing in nitrogen-free, NO3-, NO2-or NH4+medium, thus indicating a close physiological linkage between heterocyst and inorganic nitrogen metabolism regulation. © 1977 Springer-Verlag.
Heterocyst division in two blue-green algae
(Springer-Verlag, 1975) J.K. Ladha; H.D. Kumar
The heterocysts of Camptylonema lahorense and Aulosira fertilissima have been observed to undergo division, as distinct from germination, either by the constriction of the heterocyst wall and protoplast or by the formation of a transverse furrow. A two-pored heterocyst divides in this way to form two one-pored heterocysts. © 1975 Springer-Verlag.
How extensive are yield declines in long-term rice-wheat experiments in Asia?
(2003) J.K. Ladha; D. Dawe; H. Pathak; A.T. Padre; R.L. Yadav; Bijay Singh; Yadvinder Singh; Y. Singh; P. Singh; A.L. Kundu; R. Sakal; N. Ram; A.P. Regmi; S.K. Gami; A.L. Bhandari; R. Amin; C.R. Yadav; E.M. Bhattarai; S. Das; H.P. Aggarwal; R.K. Gupta; P.R. Hobbs
The rice-wheat cropping system, occupying 24 million hectares of the productive area in South Asia and China, is important for food security. Monitoring long-term changes in crop yields and identifying the factors associated with such changes are essential to maintain and/or improve crop productivity. Long-term experiments (LTE) provide these opportunities. We analyzed 33 rice-wheat LTE in the Indo-Gangetic Plains (IGP) of South Asia, non-IGP in India, and China to investigate the extent of yield stagnation or decline and identify possible causes of yield decline. In treatments where recommended rates of N, P and K were applied, yields of rice and wheat stagnated in 72 and 85% of the LTE, respectively, while 22 and 6% of the LTE showed a significant (P < 0.05) declining trend for rice and wheat yields, respectively. In the rice-wheat system, particularly in the IGP, rice yields are declining more rapidly than wheat. The causes of yield decline are mostly location-specific but depletion of soil K seems to be a general cause. In over 90% of the LTE, the fertilizer K rates used were not sufficient to sustain a neutral K input-output balance. Depletion of soil C, N and Zn and reduced availability of P, delays in planting, decreases in solar radiation and increases in minimum temperatures are the other potential causes of yield decline. A more efficient, integrated strategy with detailed data collection is required to identify the specific causes of yield decline. Constant monitoring of LTEs and analysis of the data using improved statistical and simulation tools should be done to unravel the cause-effect relationships of productivity and sustainability of rice-wheat systems. © 2002 Elsevier Science B.V. All rights reserved.
Some characteristics of two morphological mutants of Nostoc linckia induced by nitrosoguanidine
(1977) J.K. Ladha; H.D. Kumar
The blue‐green alga Nostoc linckia was treated with nitrosoguanidine and two classes of morphological mutant clones were isolated. One class shows certain abnormal phenotypic features of vegetative cells, spores, and heterocysts. It has increased heterocyst frequency and impaired growth rate. The other class exhibits an altered heterocyst spacing pattern. Both classes of mutants have reduced nitrogenase activity. Copyright © 1977 Wiley‐VCH
Trends of climatic potential and on-farm yields of rice and wheat in the Indo-Gangetic Plains
(2003) H. Pathak; J.K. Ladha; P.K. Aggarwal; S. Peng; S. Das; Yadvinder Singh; Bijay Singh; S.K. Kamra; B. Mishra; A.S.R.A.S. Sastri; H.P. Aggarwal; D.K. Das; R.K. Gupta
Rice and wheat are the two most important cereals in the Indo-Gangetic Plains (IGP) and are responsible for the food security of the region. To understand the productivity trends in the transects of the IGP: (1) the climatic potential yields of rice and wheat were simulated using a crop simulation modeling approach and (2) the long-term trends of potential and on-farm yields were compared. The potential yields of rice and wheat in the IGP ranged from 7.7 to 10.7 and 5.2 to 7.9 Mg ha-1, respectively. The upper transects of the IGP are more productive and yield decreases by 27% for rice and by 32% for wheat from transect 2 to transect 5. The rate of change in the potential yield trend of rice from 1985 to 2000 ranged from -0.12 to 0.05 Mg ha-1 per year. Negative yield trends were observed at six of the nine sites, four of which were statistically significant (P < 0.05). The decrease in radiation and increase in minimum temperature were the reasons for the yield decline. The potential yield trend of wheat, however, appeared to be stable. On-farm yields of rice also showed a negative trend but for wheat the trend was mostly positive. The adverse changes in the weather parameters and declining trends of potential and on-farm yields of rice should be taken as an indication of a future problem. Regular on-farm monitoring of crops and climatic factors is urgently needed for predicting problems and allowing measures to be taken to improve productivity. © 2002 Elsevier Science B.V. All rights reserved.
Using remote sensing technologies to enhance resource conservation and agricultural productivity in underutilized lands of South Asia
(2012) Parvesh Chandna; J.K. Ladha; U.P. Singh; Milap Punia; Raj Gupta; B.S. Sidhu
Satisfying the food demands of an ever-increasing population, preserving the natural resource base, and improving livelihoods are major challenges for South Asia. A large area of land in the Middle and Lower Gangetic Plains of South Asia remains either uncultivated or underused following the rice harvest in the kharif (wet) season. The area includes "rice-fallow," estimated at 6.7 million ha, flood-prone riversides (" diara lands," 2.4 million ha), waterlogged areas (4.9 million ha), and salt-affected soils (2.3 million ha). Bringing these lands under production could substantially improve the food supply and enhance livelihoods in the region. This paper describes a methodological case study that targeted resource-conserving technologies in underused lands of the Ballia District of eastern Uttar Pradesh (India) using multispectral remote-sensing images. Classification of temporal satellite data IRS-P6 in combination with Spot VGT 2 permitted the identification of all major categories of underused land during the post-rainy rabi/winter season, with an average accuracy of 89%. Based on three-year averages of field demonstrations, farmers gained an additional income of $63 ha-1 by introducing raised beds in salt-affected soils; $140 and $800 ha-1 by introducing deepwater rice varieties (monsoon) and boro rice (winter) in waterlogged areas; and $581 ha-1 by introducing zero-till lentil (winter) in rain-fed fallow lowland. Timely wheat planting through zero-tillage implies an additional income of $147 ha-1 and could increase wheat production by 35,000-65,000 tons in the district. The methodologies and technologies suggested in the study are applicable to more than 15 million ha of underutilized lands of the Indo-Gangetic Plains of South Asia. If the technologies are precisely applied, they can result in more than 3000 million US $ of additional income every year to these poverty prone areas. © 2011 Elsevier Ltd.
Variability of nitrogen fixation in some isolates of Nostoc linckia
(1977) J.K. Ladha; H.D. Kumar
Four clonal isolates of Nostoc linckia isolated from different localities were compared with respect to growth, nitrogen content (cellular and extracellular), and pigment composition. A considerable range of variation was observed among these isolates. This indicates the existence of genetically distinct clonal populations of the alga in natural habitats. Copyright © 1977 Wiley‐VCH