Leaf leachates

Figure 8. Radish root growth bioassay of water leachate and extract of D. illinoensis. (-) leachate (-----) leaf extract.

Cabbage, potato, radish (leaf), radish (root), grape, citrus, apple, pear, strawberry, cucurbits, green pepper, eggplant, tomato, green tea (powder), green tea (leachate) and soil... 

A variety of chemicals may be leached from the aerial portions of plants by rainwater or by fog-drip (16) including organic acids, sugars, amino acids, pectic substances, gibberellic acids, terpenoids, alkaloids, and phenolic compounds. Colton and Einhellig (17) suggested that leaf leachates of velvetleaf (Abutilon theophrasti) may be inhibitory to soybean (Glycine maxT We have recently discovered specialized hairs on the stems of velvetleaf plants which exude toxic chemicals. 

Root Exudates Leaf Leachates Volatile Inhibitors Sick Soil Toxicants... 

Leaf leachates and decanposition products Inhibitors fran leaves may be washed into the soil or compounds from leachates may further decompose into toxic products which inhibit seed germination and prevent seedling establishment (46). 

Toxicity IXiring Growing Season. It was observed that the toxicity level of leaf leachates and extracts varied according to the times sampled in the field and greenhouse. To determine... 

Leaves from the five plants were combined and divided into two equal weight samples. One sample was leached in distilled water for 2 hours at a ratio of 15 gms leaf fresh weight to 100 ml water. The leaf leachate was decanted and used directly in the bioassay. The second sample was ground in a blendor with distilled water at a ratio of 1 gm leaf fresh weight to 100 ml water. After standing for 15 min, the mixture was filtered and the filtrate was used directly in the bioassay. 

Technique for Collection of Root Exudates and Leaf Leachates... 

Each system was supported on a wooden framework so that the slope from elbow end to the screened end could be adjusted to provide adequate drainage. The pipes could be rotated in the frame so that the plants lay parallel to the ground the plant tops were sprayed with water which ran into a pan under the plants. In this way "leaf leachates" were quickly and conveniently collected. 

Both root and leaf leachates reduced germination of birdsfoot trefoil seeds. The root lengths of rape seedlings were reduced by all concentrations of leachate from fescue roots and leaves. As the concentrations of fescue leachate increased, root growth of rape was reduced. The leachate had no significant effect on the root length of birdsfoot trefoil roots. 

Root and leaf aqueous leachates of Ambrosia cumanensls did indeed produce a strong inhibition on the growth of weed species. Aqueous extracts of soil collected under A.cumanensls in July (during its flowering) were strongly allelopathic to weed growth. Decomposition of leaves and roots in pots caused inhibition of some weeds also. Microorganisms have a major role in this process, as shown by results from sterile and nonsterile soils (17). 

Leucaena leaf leachate, even though the leaf juice of pudica contains a relatively high amount of mimosine. Among 84 seedlings of pudica tested only 2 seedlings survived, showing that mimosine can be practically useful to control a notorious weed such as M. pudica in the field. 

Allelopathic chemicals from plants may be released from living leaves as volatiles or leachates or from roots through exudation or sloughing off of dead tissues. They also may be leached from leaf litter on the soil surface. 

Table IV. Effect of Fescue Leaf Leachates on the Growth...

The clover plants were 1 month old when the applications of fescue leaf leachates were initiated. The leachates were applied to the soil daily for 1 month when the cover was harvested. 

Synthesis of concentrations and fluxes of DOC and DON in precipitation, throughfall, and soil organic and mineral horizons are often reported in the published literature (Willey et al., 2000 Michalzik et al., 2001 Neff and Asner, 2001 Neff et al., 2002). Dissolved organic matter from these sources contributes DOM to groundwater and surface water. Leaf litter leachate is documented as a major source of DOC in the soil water of forested watersheds (Hongve, 1999) and in surface waters (Wetzel and Manny, 1972 McDowell and Fisher, 1976). However, specific quantitative allocation of DOC and DON from roots, leaf litter, and the forest floor in soil solution remains uncertain. 

Dahm, C. N. 1981. Pathways and mechanisms for removal of dissolved organic carbon from leaf leachate in streams. Canadian Journal of Fisheries and Aquatic Sciences 38 68—76. 

Plants release allelochemicals as volatiles, leaf leachates, and root exudates. In addition, all the constituents of plant residues are eventually released into the environment through microbial decomposition. During this process, most allelochemicals lose their activity but some compounds, for example, benzoxazinoids (cyclic hydroxamic acids), can be activated after hydrolysis.1-3... 

Additional information on how leaf litter potentially interacts with acid rain was contributed by Lee V7eber (2 ). In their experiments, acid rain was simulated in a field situation on sugar maple and red alder. Rain as throughfall was allowed to interact with leaf litter and the leachate was collected. Litter leachate was found to be higher in S0 , Ca+ and Mg+, and the pH was found to have increased. Thus, they hypothesized that the litter was neutralizing the simulated acid rain, with red alder litter being more effective than sugar maple. 

Heavy rains leach out a portion of the bases in the mull layer and below, most of which are intercepted by the tree roots and returned to the surface again later with the annual leaf fall. Since the leachates are usually nearly neutral in reaction, they extract less mineral matter than where the percolating water is high in organic and nitric acids. This continuous cycling of nutrients accounts for stabilization of the soil with little tendency toward the distinct stratification and impoverishment that is characteristic of true podzols. 

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