Root Elongation In Response Research Articles

Seedling responses to band applied NH4OH rates and to N form in two maize hybrids

Growth of maize seedlings can be improved by enhanced ammonium nutrition, but placing fertilizer anhydrous ammonia close to seedlings introduces the risk of ammonia toxicity. In this study, growth and root elongation response to rates of closely placed NH4OH bands were investigated in two contrasting maize hybrids. Seven rates of NH4OH, ranging from 0 to 200 mg N kg-1 soil were injected into the center of each pot. A single rate of Ca(NO3)2-N was included to compare hybrids for N form preference at a moderate N rate. Three seedlings per pot were planted 5.7 cm from the injection point.

ROOT AND SHOOT GROWTH AS INFLUENCED BY OVERHEAD AND FLOATATION IRRIGATION IN JALAPENO PEPPER TRANSPLANTS

This study was conducted to investigate how irrigation systems alter root elongation, root morphology, shoot growth characteristics and yield of `TAM-M' jalapeno pepper seedlings. Transplants were grown in containerized trays (18 cm3/cell) for 6 weeks in a greenhouse in Spring 1991. Irrigation systems were: a) floatation (FI), b) 4-week floatation plus 2-week overhead (FI+OI); c) alternate floatation and overhead (FI/OI), and d) overhead (OI). The growing media was maintained between 50 and 20% of its water holding capacity. Between 20 and 41 days after seeding (DAS), FI and FI/OI transplants maintained a constant lateral root length increase. In both FI+OI and OI transplants, lateral root elongation response tended to a `plateau' at ≈ 31 DAS. However, between 31 and 41 DAS, OI transplants had a root growth compensation, increasing the number and length (33%) of basal roots. In FI+OI transplants, basal root growth compensation occurred later in the field. At planting, OI transplants had higher shoot/root ratio (S:R=5) and maintained a higher shoot water potential (ψ= -0.58 MPa) than FI transplants (S:R=3; ψ= -0.69 MPa), respectively. Overhead-irrigated transplants had higher early fruit yields than floatation-irrigated transplants, but total yields were unaffected.

Promotion of root elongation by phosphorus deficiency

Decrease of culture solution pH and increase in cation/anion ratio in the plant were observed when horsegram (Macrotyloma uniflorum (Lam.) Verdc.) was grown in solution culture deficient in phosphorus. The effux of H+ from the roots of −P plants was observed in bromocresol purple agar. The length of root cells was considerably increased by −P treatment. Thus a close correlation between H+ excretion, length of the root cells and root elongation in response to P deficiency was established.

Day-neutral flowering in some Desert Blepharis spp.

In the desert areas of Israel, Sinai and the neighbouring countries, there are three species of Blepharis. In addition at least six different populations of types not yet classified were also found in various locations and habitats. Differences such as rates of root elongation in response to temperature, structure of inflorescences and spiny bracts, and mechanisms of seed dispersal were found in these species and types. In all of them, irrespective of the growing conditions, three pairs of leaves and one terminal inflorescence develop above the cotyledons. A lateral branch from the axil of each of the pairs of upper leaves bears two pairs of leaves and a terminal inflorescence. From these branches, additional lateral branches sometimes appear in the axil of two upper leaves, again bearing two pairs of leaves, and a terminal inflorescence, and so on. Flowering in these plants was found to be day-neutral. The quantity and distribution of rain, soil humidity and temperature seem to regulate the age of the plant at flower-bud appearance and flowering. The ecological importance of this behaviour is discussed.

Dynamics of root growth and decay in two grasses native to semi‐arid Argentina

AbstractThe pattern of root growth and decay in Stipa tenuis Phil, and Piptochaetium napostaense (Speg.) Hack, was examined under field conditions in root observation chambers. The roots of both species grew uninterruptedly throughout the whole year. Root elongation during spring, summer, and early autumn can be six and five times as high as that in the late autumn to winter period for S. tenuis and P. napostaense, respectively. Root decay was a continuous process in both species throughout the year, with maximum decay rates occurring from late spring through to the middle of autumn. Comparison of minimum and maximum values registered during the year showed a root decay ratio of about 4:1 for S. tenuis and one of 5:1 for P. napostaense. During the period of maximum root growth, both species showed a pulse‐like pattern of root elongation in response to rapid changes in water availability. In a semi‐arid region in which the soil is notably shallow, root growth behaviour of this kind should allow these species to respond opportunistically to water.

Genotypic Differences in Aluminium Tolerance of Soybean ( Glycine max L.) as Affected by Ammonium and Nitratenitrogen Nutrition

Soybean ( Glycine max L.) genotypes differed considerably in response of root elongation to aluminium supply in solution culture. Root elongation was more sensitive to Al than nitrate and ammonium net uptake rates, which were higher in Al treated plants. Nitrate reductase activity, which was also higher in Al treated plants in more basal root zones, was unaffected on a much higher activity level in the apical 2 mm root zone. Genotypic differences in Al tolerance were not related to differences in NH 4 + versus NO 3 - uptake, nitrate reductase activity and related changes of pH in the rhizosphere. This was confirmed by a sand culture experiment comparing NH 4 + and NO 3 - nutrition and direct measurement of pH at the root surface along the roots.

Aluminium tolerance and calcium efficiency of cowpea genotypes

Abstract Cowpea (Vigna unguiculata) seedlings were grown in solution culture for 4 days in a growth chamber at different levels of Ca and Al. Increasing the Ca supply completely eliminated inhibition of root elongation by Al. This was mainly due to decreasing Al concentrations especially in the root tips. Increasing Al supply depressed Ca concentrations in all root tissue uniformly. Inhibition of root elongation by Al could be explained by induction of Ca deficiency as indicated by the Ca concentrations of the root tips compared to plants with limited Ca supply. Fifty‐five cowpea genotypes differed considerably in response of root elongation to Al. When 10 genotypes were cultivated with high and low Ca supply, important genotypical differences in Ca requirements for dry matter production were observed. A positive relationship between Al tolerance and Ca efficiency of the genotypes was generally noted. Even though Ca efficiency appeared to be a prerequisite for Al tolerance, Ca efficiency did not guarantee...