Shoot and root residues

To determine the respective importance of shoot and root residues in regulating early broadleaf weed seedling emergence, and... 

Determine the Respective Importance of Shoot and Root Residues in Regulating Early Broadleaf Weed Seedling Emergence (Blum et al. (2002) Summarized with Permission of International Allelopathy Foundation)... 

Figure 10.4 Residue patterns in alfalfa and rye grass shoots and roots from the microcosm after chemical applied as a seed treatment. [Reproduced with permission from J. D. Gile and...

Since for the 1992 and 1993 no-till field studies (Blum et al. 1997) both root and shoot residues of rye, wheat, crimson clover, and subterranean clover were present in each no-till plot, the role of shoot or root residues alone on weed seedling emergence could not be determined. Thus for the 1996 and 1997 field studies, sets of no-till plots with only root residue (i.e., shoots removed), only shoot residue (i.e., cut shoots from root plots placed on no-till reference plots), and shoot (uncut and cut but left in place) and root residues were included in the experimental design (Blum et al. 2002). However, to make the 1996 and 1997 field studies more manageable, only one cover crop, wheat, was utilized. 

In summary, organic no-till systems are recommended only where high-residue cover crops can be grown and managed properly, and when productivity of cash crops is favourably affected by root and shoot biomass (surface residue mulch) of the cover crops. Research and grower experience have shown that organic no-till systems are most likely to succeed ... 

Plants. Absorbed by the roots and translocated to the shoots. The major residue in rice was carpropamid... 

In a series of studies by Cataldo et al. [64] and Harvey et al. [65], the uptake and fate of TNT was evaluated for plants grown in three types of soils (Table 10.3) amended with unlabeled and radiolabeled TNT. Plant tissues and soil were evaluated by chemical extraction and analysis methods that permitted resolution of parent TNT and more polar components. Bush bean, blando brome, and wheat shoot tissues accumulated an average of 27%, 37%, and 17% of the plant accumulated radiolabel of [14C]TNT, respectively. Plant uptake was inversely proportional to soil organic matter. Analysis of TNT and TNT-derived residues show that >80% of all accumulated and transported residues were either polar or conjugated metabolites of TNT-derived compounds [66], Table 10.4 presents the range of detectable TNT concentrations in the root and shoot sections of wheat and blando brome in the three various soil types. 

Soil extractions cannot differentiate between sources of phenolic acids, e.g., are they from shoots or roots of the putative allelopathic plant or the receiving plant, are they from plant residues on or in the soil, are they from faunal and microbial activity on new or old organic residues in the soil, etc. 

Petri dish bioassays of residues in soil—(1) segments of ground dried shoots cut from the soil surface 35 days after planting, (2) 2-cm segments of roots rinsed free of soil, and (3) aqueous extracts of shoot segments, 50 g extracted with 1 L distilled H2O—confirmed phytotoxicity. Petri dishes were filled with oven-dried sterile soil or nonsterile soils, and dried residues were uniformly spread and watered with distilled water, or in the case of extracts, added directly. Dishes were incubated for 72 h at 27°C in a growth chamber. 

TABLE VI. Residues (ppm on Fresh Weight Basis) of Glyphosate and N-Nitrosoglyphosate in Roots and Shoots of Oat Plants Grown in the Treated Soil ... 

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