Department of Plant Sciences

Factors that inhibit the growth of plants in strongly acidic soils include low pH and aluminum excess. We evaluated two Myrtaceae species (Melaleuca cajuputi and Melaleuca bracteata), which are useful trees in tropical regions due to their resistance to low pH and excessive aluminum, to determine their response characteristics to environmental stresses. The results revealed that M.cajuputi, the growth by the aluminum concentration was not inhibited. However, the root growth of M.bracteata, by the aluminum treatment was inhibited remarkable, and 83.2% inhibited the maximum more than aluminum free. The pH of rhizosphere of both plants has decreased by the BCP plate. However, the pH decrease has decreased as for M. bracteata with high concentration of aluminum, but M.cajuputi is not changed. Next, it was able to be confirmed of aluminum accumulated in the root M.bracteata more than M.cajuputi by hematoxylin and aniline blue dyeing. At the result, it was able to be confirmed of aluminum accumulated in the root M.bracteata more than M.cajuputi. As for M.bracteata, aluminum was absorbed in the inner-cell of the root tissue. On the other hand, M.cajuputi had aluminum only in the surface of the root. We concluded that M.cajuputi was an aluminum tolerance because the mechanism that aluminum doesn't invade the internal tissue of the root was possessed.

Boron (B) is an essential trace element for higher plants yet it becomes toxic when present at high concentrations. The site of B toxicity in plant roots is located in the root tip, and B tolerance is associated with the concentration of reducing sugars (RS) in this region. In the study reported here, we aimed to detect and map loci associated with this trait using a barley doubled-haploid population derived from a cross between Clipper (B sensitive) and Sahara 3771 (B tolerant). The population was screened at high B supply using solution culture, with the RS concentration measured in the root tip. The RS concentration varied widely in the parents and DH lines, ranging from 14 to 141 mg g-1. Using a linkage map of 420 molecular markers, quantitative trait loci (QTL) were detected on chromosomes 2H, 3H, 5H and 6H. Of these, the QTL on 2H had the largest effect, explaining 16% of the phenotypic variance, with the (high RS) allele contributed from Sahara 3771. QTLs detected here were co-located with reported loci for other B tolerance traits, including leaf symptom, relative root elongation and B uptake, indicating a role of RS in physiological pathways associated with B tolerance.

Acacia mangium Willd. is a highly Al-resistant leguminous tree with modest organic anion exudation from roots. We have recently found the root apices of A. mangium to be surrounded by detached tissues with a unique structure under hydroponic conditions. To understand high Al tolerance mechanisms, we examined the roles of a cap-like structure on the Al-resistant root growth in A. mangium. The structures were autonomously sloughed off the root, and redeveloped within a week. Al only slightly inhibited the elongation of roots both with or without a cap-like structure. However, the removal of a root caplike structure facilitated Al-inducible root bending that only occurs immediately after the exposure. This facilitated root curving appears to be a major factor in slight enhancement in Al-induced root elongation inhibition in roots without a cap-like structure. The anchor position of a whole root cap-like structure to the root was limited to the columella cap region, where their connection became more rigid with longer Al-exposure periods. These results suggest that cap-like structures around the root may play a role in protecting root cap cells from the immediate impact of Al.

Most of plants uptook NO3--N faster at the low pH 4.0 than at pH 6.0 and uptook NH4+-N slower, but few experimental plants showed different tendency. The exceptions probably due to excessive nitrate outflux of some maize and wheat varieties (Suyu 19. Zhendan958 and Yangmai12) at low pH. Some other experimental plants (Huaidao 8. Nongda108 and Yangmai12) even show no obvious NH4+ toxic symptoms at pH 4.0. The effect of low pH on uptake rate of NH4+-N and NO3--N varied with plant species, varieties, and the difference increased with the growth age of seedlings.

An experiment was undertaken at District Seed Farm of Bidhan Chandra Krishi Viswavidyalaya, Mohanpur, Nadia, West Bengal, India to evaluate the F1 hybrids of okra under reduced level of chemical fertilizers (50% of recommended dose of fertilizers) with two sources of organic manures (Cow-dung manure @ 25 t/ha and neem cake @ 2.5 t/ha). The results indicated significant differences among the hybrids and between the sources of organic manures for both vegetative growth characters such as plant height, number of primary branches/plant and nodes/plant; reproductive behaviour of the plant, i.e. days to 50% flowering as well as fruit characters like fruit length, girth, weight, fruits/plant and marketable fruit yield. Based on the results it may be concluded that under the agro climatic conditions of West Bengal, the hybrids NOH-15, Makhamalli, Sun 40, Sun 08, Mahyco Bhendi No.12, Mahyco Bhendi No.10, Mahyco Bhendi No.1 as well as Vijaya (99.36 – 107.43 q/ha) can be recommended for commercial cultivation under reduced level of chemical fertilizers during summer. Application of neem cake @ 2.5 t/ha along with reduced level of fertilizer (50% RDF) is very much beneficial for better vegetative growth with increasing the yield in okra.

The efficiency with which cotton plants redistributed N from the vegetative to the reproductive organs in three cotton crops in north-west NSW, Australia that differed in yield potential was examined. It is generally assumed that differences in boll numbers result in corresponding changes in the demands placed on leaves and stems for the supply of the N required for boll production. Cotton plants were partitioned into leaves, stems and fruit every ten days from flowering to maturity. The N content of these fractions differed between the crops: the lowest-yielding crop (2130 kg lint/ha) had the highest proportion of N in the fruit (74%), whereas the highest-yielding crop (3270 kg lint/ha) had the lowest (64%). The lowest-yielding crop redistributed 55% of its leaf-N and 7% of its stem-N to the fruit, while the highest-yielding crop redistributed 24% of leaf-N and 8% of the stem-N. These findings indicated that higher boll loads (increasing the demand for N) in situations where nitrogen is a non-limiting factor will not necessarily equate to a higher N-use efficiency. Differences in redistribution of N are more likely caused by complexities of water, other nutrients and environmental conditions. This information can be used to better understand the way high yielding crops use N, and to aid in optimising the N use efficiency of high yielding cotton crops.

The cultivation of maize is one of the most important crops for the the Brazilian Agribusiness, representing 6.4% of world production. It should be noted that world production is almost 800 million tons and the United States is responsible for 42% of total production. Nitrogen fertilization is a very important step for the production system of maize, both in the aspect of quantification of doses, and in defining the time of application. The use of portable chlorophyll meter has been widely used, especially in tests of calibration and evaluation of deficiency, on the other hand, there is no literature on using the chlorophyll meter to indicate the amount of N to be applied. The experimental design was the randomized completely blocks with four replications and 6 treatments with nitrogen fertilization by coverage (0, 60,100, 120, 140 and 160 kg N ha-1) using urea. There is verified positive relationship between N rates and nitrogen content and it was affected by increasing doses of this nutrient, until 120 kg N ha-1. The curve of nitrogen fertilization using the Chorophyll meter was possible by the excellent correlations between doses and readings, doses and N content, and doses and grain yield. It was concluded that there was a good correlation between levels of nitrogen applied in coverage, with ICF readings, nitrogen content and and grain yield. Is possible to establish a curve for the nitrogen fertilization by the ICF readings at the time of covering.

The growth and mineral nutrition were investigated in seedlings of four varieties of commercial tomato Marmande, Coeur de Boeuf, Roma and a “cherry”- type tomato variety Cocktail, in nutritive solutions containing 0 or 100 mM NaCl. Salt decreased total dry weight of all varieties but with different degrees. Cocktail was the most tolerant whereas Coeur de Boeuf the most sensitive. Na+ and Cl- uptake and transport increased by the presence of NaCl. Na+ accumulation varied among the varieties as follows: Roma< Coeur de Boeuf

A pot culture experiment was conducted at the College of Horticulture, Kerala Agricultural University, India, to study the effect of potassium- magnesium interaction in plants using okra (Abelmoschus esculentus Moench) as the test crop. The experiment was conducted on an alluvial soil, sandy clay in texture, acidic (pH- 4.9), high in organic carbon, and medium in available phosphorus (P) and potassium (K). The treatments included factorial combinations of four levels of potassium from K0 to K3 (0, 15, 30 and 45 kg K2O ha-1 as muriate of potash) and four levels of magnesium (Mg) from Mg0 to Mg3 (0, 10, 20 and 30 kg MgO ha-1). At all K levels, combined with Mg application at 10 kgha-1, an increase was observed in dry matter production but at higher levels of Mg a decrease occured. Increasing the level of K from K0 to K3 in the presence of low levels of Mg caused a progressive increase in the yield while at higher Mg levels increasing K reduced the yield. Increased addition of K without Mg significantly increased the crude protein contents. Application of Mg generally decreased the crude protein content of harvested fruits. Increasing the rate of K application also progressively and significantly decreased the crude fibre. The magnitude of decrease was increased in the presence of Mg. At all levels of Mg, as the K application rates increased, the ascorbic acid content also showed a significant increase.

Addition of Mg caused a significant increase in the nitrogen (N) uptake at each level of K though the magnitude of increase diminished as levels of Mg increased. The application of high rates of Mg decreases the favorable effect of K on P uptake and hence Mg is seen to have an antagonistic effect on P uptake. A positive interaction existed between K and Mg on the uptake of K. At higher levels of K, a significant increase in K uptake was noticed as Mg levels were increased. Calcium (Ca) uptake was significantly reduced with increasing K levels especially in the absence of Mg. Though K application up to K2 caused a non significant increase in Mg uptake, further increase to K3 reduced the uptake. In the presence of a particular level of Mg, increasing the K levels did not bring about a significant variation in the sulphur uptake by the plant.

To avoid iodine toxicity in crops and to make iodine-biofortified crops, it is important to study iodine uptake and metabolism in plant depending on its chemical forms. Using ion chromatography and inductively coupled plasma-mass spectrometry system (IC-ICP-MS) for the determination of form of iodine, plant uptake and metabolism of inorganic iodine and the behavior in the rhizosphere were studied. Iodide was detected in plant body, xylem sap and culture media of Iodate treated plants. Iodate would be reduced to Iodide by roots or in the rhizoshere readily, and rice plants would absorb the reduced Iodide. Higher plants would have the ability to reduce iodate to iodide.