Root Length Production Research Articles

Allocation, within and between organs, and the dynamics of root length changes in two birch species.

Spatial and temporal dynamics of biomass allocation within and between organs were investigated in seedlings of two birch species of contrasting successional status. Seedlings of Betula alleghaniensis Britt (yellow birch) and B. populifolia Marsh (gray birch) were grown for 6 weeks at two nutrient levels in rectangular plexiglass containers to allow non-destructive estimates of root growth, production and loss. Leaf area and production were simultaneously monitored. Yellow birch responded more to nutrient level than gray birch in terms of total biomass, shoot biomass, leaf area and root length. Yellow birch also flexibly altered within-organ allocation (specific leaf area, specific root length and specific soil amount). In contrast, gray birch altered between-organ allocation patterns (root length:leaf area and soil amount:leaf area ratios) more than yellow birch in response to nutrient level. Yellow birch showed greater overall root density changes within a very compact root system, while gray birch showed localized root density changes as concentric bands of new root production spread through the soil. Species differ critically in their responses of standing root length and root production and loss rates to nutrient supply. Early successional species such as gray birch are hypothesized to exhibit higher plasticity in varied environments than later successional species such as yellow birch. Our results suggest that different patterns of allocation, within and between plant organs, do not necessarily follow the same trajectories. To characterize thoroughly the nature of functional flexibility through ontogeny, within- and between-organ patterns of allocation must be accounted for.

RELATIVE VIABILITY AND VIGOUR OF DIFFERENT GENOTYPES OF SOYBEAN (Glycine max (L.) Merril) DURING STORAGE

Seed viability and vigour studies with the twenty seven genotypes of soybean brought out the genotypic differences for germination potential, root and shoot length and dry matter production of the seedlings in storage. Large seeds retained by 15/64" (aperture width 6.00 mm) sieve maintained the viability and vigour during eight months storage period with minimum loss compared to medium and small seeds retained by 14/64" (aperture width 5.60 mm) and 13/64" (aperture width 5.20 mm) sieves.

Costs and benefits of constructing roots of small diameter

Abstract Roots represent a considerable carbon cost for plants. Furthermore, plants vary considerably in how carbon is expended for belowground processes. One attribute that varies widely among species is the investment of root biomass in the production of root length. Relatively thin roots have a high specific root length (SRL) or length: dry weight ratio. Since water and nutrient uptake is based more upon root length than mass, one might conclude that species of high SRL invest their root biomass more efficiently than species of low SRL. This, however, ignores many other functional attributes of roots that may permit coarse lateral roots to be more adaptive than fine lateral roots under certain environmental conditions. In leaves, studies on the relationship of structure and function suggest that evergreen plants with greater leaf longevity commonly have thicker leaves, lower photosynthetic capacity, and lower respiration rates than deciduous plants. These kinds of relationships may also be true for thi...

The Demography of Fine Roots in a Northern Hardwood Forest

The production, development, and mortality of fine roots in a northern hardwood forest was monitored for 1 yr using minirhizotrons. Roots were divided into two strata based upon their depth in the soil, <30 cm and >30 cm. Cohort analyses of roots produced in the spring of 1989 revealed that while almost 50% of fine roots at both depths survived after 346 d, the number of white roots in each cohort declined very rapidly. Virtually all roots had turned brown after 346 d. The probability of a surviving white root turning brown was much greater than the probability that it would die at all times of the year, and the bulk of root mortality was accounted for by brown roots. Analysis of root length production and mortality showed that total annual length mortality at the <30 cm depth was 76% of the initial standing crop and 110% at >30 cm depth. Fine root production and mortality occurred simultaneously throughout the year, and production was slightly greater than mortality at both depth. Total root length peaked in the summer at both depths, and overwinter production and mortality as rather low. Production of white and brown root length indicated that roots near the soil surface were undergoing much more rapid rates of browning than deep roots. Loss of root length between sampling dates was largely due to roots that died and rapidly decayed or otherwise disappeared.

The influence of inorganic nutrient fertilization on the growth, nutrient composition and vesicular-arbuscular mycorrhizal colonization of pretransplant rice (Oryza sativa L.) plants

The effects of P, N and Ca+Mg fertilization on biomass production, leaf area, root length, vesiculararbuscular mycorrhizal (VAM) colonization, and shoot and root nutrient concentrations of pretransplant rice (Oryza sativa L.) plants were investigated. Mycorrhizal plants generally had a higher biomass and P, N, K, Ca, Mn, Fe, Cu, Na, B, Zn, Al, Mg, and S shoot-tissue nutrient concentrations than non-mycorrhizal plants. Although mycorrhizal plants always had higher root-tissue nutrient concentrations than non-mycorrhizal plants, they were not significantly different, except for Mn. N fertilization stimulated colonization of the root system (colonized root length), and increased biomass production and nutrient concentrations of mycorrhizal plants. Biomass increases due to N were larger when the plants were not fertilized with additional P. P fertilization reduced the colonized root length and biomass production of mycorrhizal plants. The base treatment (Ca+Mg) did not significantly affect biomass production but increased the colonized root length. These results stress the importance of evaluating the VAM rice symbiosis under various fertilization regimes. The results of this study suggest that pretransplant mycorrhizal rice plants may have a potential for better field establishment than non-mycorrhizal plants.

Studies on the allelopathic effects of some agroforestry tree crops of Garhwal Himalaya

The allelopathic effects of Adina cordifolia, Alnus nepalensis, Celtis australis and Prunus cerasoides were tested by growing crops of Eleusine coracana, Glycine max and Hordeum vulgare on top soil, rhizosphere soil from the plantation of these trees, and on field soil either mulched with dry leaves or irrigated with aqueous leaf extracts of the agroforestry tree species. Germination percentage, shoot length, root length and dry matter production and pigment contents of crops were depressed by agroforestry tree crops. Maximum reduction in germination percentage, root-shoot length and dry matter production was obtained with experimental garden soil mulched with dry leaves of trees and by the effect of Adina cordifolia followed by P. cerasoides, H. vulgare proved most susceptible and E. coracana highly resistant to these tree-top interactions.

Effects of humic acid-herbicide interactions on the growth of Pisum sativum in nutrient solution

Slight increases in root length and dry matter production were measured in roots and shoots of Pisum sativum seedlings, when germinated seeds were grown for eight days in a controlled environment chamber, on Nitch nutrient solution to which 10 mg L-1 soil humic acid (HA) had been added. A concentration of 100 mg L-1 of HA produced a small reduction in dry matter production of shoots. In the presence of herbicides, 10 mg L-1 cycluron or 100 mg L-1 prometone, root elongation and shoot growth was reduced by varying degrees with respect to the control. Nutrient solutions containing 100 mg L-1 cycluron, 10 or 100 mg L-1 alachlor, or as little as 0.1 mg L-1 of 2,4-D resulted in an almost complete suppression of the growth of pea seedlings. The addition of 10 or 100 mg L-1 of HA to nutrient solution containing the herbicide was found to be either ineffective in enhancing growth, or even further reduced growth, compared to samples grown in the presence of the herbicide alone. The results of this preliminary study suggest that the generally accepted view that humic substances exert a positive effect on plant growth may not occur when humic substances interact with herbicides.

Root production and root turnover in two dominant species of wet heathlands.

Root biomass production, root length production and root turnover of Erica tetralix and Molinia caerulea were estimated by sequential core sampling and by observations in permanent minirhizotrons in the field. Root biomass production, estimated by core sampling, was 370 (Erica) and 1080 (Molinia) g m-2 yr-1. This was for both species equal to aboveground production. Assuming steady-state conditions for the root system, root biomass turnover rates (yr-1), estimated by core sampling, were 1.72 (Erica) and 1.27 (Molinia). Root length production of both species, estimated by minirhizotron observations, varied significantly with observation depth. Root length turnover rate (yr-1) of both species did not vary significantly with observation depth and averaged 0.92 in Erica and 2.28 in Molinia. Reasons are given for the discrepancy between the results of the two types of turnover measurements. The data suggest that the replacement of Erica by Molinia in a wet heathland, which occurs when nutrient availability increases, leads to an increased flow of carbon and nutrients into the soil-system. Therefore, there may be a positive feedback between dominance of Molinia and nutrient availability.

Effect of Antagonists in Combination with Carbendazim Against Macrophomina phaseolina Infection in Cowpea

Pelleting of cowpea seeds with Trichoderma viride Pers: fr. either alone or in combination with carbendazimm inhibited the growth of Macrophomina phaseolina Tassi (Gold.) in vitro . The treatment increased the germination and reduced the post emergence mortality under pot culture conditions. Carbendazim did not show any adverse effect on the antagonists T. viride and T. harzianum Rifal under in vitro and also in pot culture studies. Seed pelleting with carbendazim in combination with antagoinst reduced the seedling mortality besides enhancing the growth characteristics like shoot length, root length and dry matter production.

Root dynamics of tallgrass prairie in wet and dry years

Root dynamics were studied using root windows at Konza Prairie, a tallgrass prairie in north central Kansas, during dry (1984) and wet (1985) years. Amounts, production, and disappearance of root length decreased during drought but increased when rains resumed; however, standing crop remained low. The 1985 root lengths increased throughout the growing season, while production and disappearance remained constant. Yearly summaries of amounts, productivity, and decomposition by 10-cm increments in soil depth show that the effect of drought on these variables decreased with increasing soil depth. Turnover rates of root length averaged 564 in the dry year versus 389% in the wet year, with the largest difference noted in the 0- to 10-cm depth (800 in 1984 versus 540% in 1985). Production and decay patterns observed using root windows were also noted in root biomass data (obtained from soil cores). The average total root biomass turnover rate was 31%. Failure to sort below-ground materials into tissue types (rhizomes, roots) and live versus dead status results in reduced estimates of biomass turnover rates. The greatest possible separation of plant components presents the most comprehensive picture of (belowground) growth dynamics.

STUDIES ON THE ALLELOPATHIC EFFECTS OF SOME AGROFORESTRY TREE CROPS

SUMMARY The allelopathic influence of Eucalyptus tereticornis, Casuarina equisetifolia and Leuceana leucocephala was tested by growing crops of sorghum, cowpea and sunflower on topsoil and rhizosphere soil from plantations of those trees or on field soil either mulched with dry leaves or irrigated with aqueous leaf extracts. Crop germination, root length and dry matter production were depressed. Maximum reductions were obtained with top soil and by the effect of eucalyptus. Sorghum proved most susceptible to these influences.