Suppression of Coastal Heath Vegetation by Eucalyptus baxteri

1978 ◽  
Vol 26 (2) ◽  
pp. 203 ◽  
Author(s):  
RD Moral ◽  
RJ Willis ◽  
DH Ashton
Keyword(s):  
Triticum Aestivum ◽  
Water Potential ◽  
Similar Pattern ◽  
Dominant Species ◽  
Soil Nutrient ◽  
Direct Transfer ◽  
Eucalyptus Viminalis ◽  
Root Absorption ◽  
Coastal Heath ◽  
Chemical Inhibition

Eucalyptus baxteri produces a zone of suppression beneath its canopy when growing in coastal heath. Dominant species including Casuarina pusilla and Leptospermum myrsinoides are suppressed, but species such as L. juniperinum and Xanthorrhoea australis are not. Investigations of shoot water potential, soil nutrient levels and shading failed to suggest suppression by competition. E. nitida produces a slightly deeper shade but fails to produce a similar pattern of differential suppression. Chemical inhibition (allelopathy) of Casuarina pusilla, Eucalyptus viminalis and Triticum aestivum by E. baxteri was shown to exist under laboratory conditions. Foliar leachates of E, baxteri are inhibitory in bioassays and contain gentisic and ellagic acids. Litter leachates are also inhibitory in bioassays and contain gentisic, gallic, sinapic, caffeic and ellagic acids. Both leachates also contain several unknown phenolic aglycones, numerous glycosides, and terpenoids. Topsoil extracts are also inhibitory and contain resins and, possibly, terpenoids. The suppression zone is associated with the allelopathic ability of E. baxteri, and is maintained either through the direct transfer of foliar leachates to leaves of suppressed species, through root absorption of foliar and litter leachates, or as a consequence of mycorrhizal inhibition by such leachates.

Root Growth, Water Uptake and Canopy Development in Eucalyptus viminalis Seedlings

1994 ◽  
Vol 21 (1) ◽  
pp. 69 ◽  
Author(s):  
JG Phillips ◽  
SJ Riha
Keyword(s):  
Root Growth ◽  
Water Potential ◽  
Soil Water ◽  
Water Loss ◽  
Soil Water Potential ◽  
Water Extraction ◽  
Soil Conditions ◽  
Lower Section ◽  
Canopy Development ◽  
Eucalyptus Viminalis

A split-root experiment was conducted using Eucalyptus viminalis seedlings which were exposed to three watering regimes in order to investigate root growth and soil water extraction under conditions of a drying soil profile. Seedlings were grown in columns in which the soil was divided horizontally with a soft wax plate. Watering treatments were composed of (1) both upper and lower sections of the column well watered (W/W), (2) only the lower section well watered (D/W), and (3) water withheld completely from both upper and lower sections (D/D). Daily measurements included soil water potential (Ψs), column water loss and leaf elongation. Increase in above- and below-ground biomass was deter- mined from initial and final harvests after 25 days of treatment. Whole-column water loss and leaf extension were depressed as Ψs in the upper section of D/W and D/D decreased to -0.4 MPa over the first 8-10 days. However, water loss did not decrease significantly in the lower section of treatment D/W relative to the lower section of treatment W/W during this period. This indicated that water extraction by roots remaining in wet soil was not severely inhibited by the decrease in transpiration associated with the soil conditions in the upper profile. Root distribution at the end of the experiment indicated significant growth in the lower section of treatment D/W. There was evidence that hydraulic lifting of water between column sections may have occurred, as periodic increases in soil water potential of the unwatered upper section of D/W were observed.

Differential Absorption and Translocation of Metribuzin by Downy Brome (Bromus tectorum) and Winter Wheat (Triticum aestivum)

Weed Science ◽  
1987 ◽  
Vol 35 (1) ◽  
pp. 1-5 ◽  
Author(s):  
Daniel L. Devlin ◽  
David R. Gealy ◽  
Larry A. Morrow
Keyword(s):  
Triticum Aestivum ◽  
Winter Wheat ◽  
Bromus Tectorum ◽  
Wheat Root ◽  
Downy Brome ◽  
Fresh Weight Basis ◽  
Plant Parts ◽  
Root Absorption ◽  
Treated Leaf ◽  
Total Plant

Foliar and root absorption and translocation of metribuzin (4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one) by downy brome (Bromus tectorumL. # BROTE) and winter wheat (Triticum aestivumL.) was determined. After a 48-h absorption period, roots of three-week-old downy brome plants had absorbed two times more metribuzin on a total plant fresh weight basis than had roots of winter wheat. Root-absorbed metribuzin was translocated similarly regardless of species with 80% of absorbed14C accumulating in leaf blades, 10% in the leaf sheaths, and 10% in the roots. After 24 h, leaves of downy brome and winter wheat had absorbed, respectively, 26 and 36% of foliar-applied metribuzin, and absorption increased threefold with the addition of a nonionic surfactant. Translocation of foliar-absorbed metribuzin was primarily towards the apex of the treated leaf. No translocation from the treated leaf to other plant parts occurred with either species. The greater tolerance of winter wheat to metribuzin is due in part to less root absorption of metribuzin by winter wheat than by downy brome.

scholarly journals WHEAT CULTIVARS: RESPONSE TO IRRIGATION AND SOWING DATES

1996 ◽  
Vol 53 (2-3) ◽  
pp. 217-222
Author(s):  
A.E. Klar ◽  
T. Hossokawa
Keyword(s):  
Triticum Aestivum ◽  
Water Potential ◽  
Soil Water ◽  
Aluminium Toxicity ◽  
Triticum Aestivum L ◽  
Wheat Cultivars ◽  
Growing Seasons ◽  
Yield Level ◽  
Sowing Dates ◽  
Similar Yield

This study was carried out in an Alfisol-Oxisol transition sandy-clay texture, using six wheat cultivars (Triticum aestivum, L.): two tall and tolerant to soil aluminium toxicity (BH-1146, and IAC-18), and four semi-dwarf cultivars - Anahuac, IAC-162, IAC-24, and IAC-60 - of which only the first two are sensitive to soil aluminium toxicity. Two minimum soil water potentials (ys) levels were used: 1. watered, when Ys reached about -0.05 MPa; 2. dry, when the water potential reached around -1.5 MPa. Two sowing dates, 05/22/92 and 06/11/92, were used. The results showed that Anahuac and IAC-60 are the most indicated cultivars for the studied region; when irrigated all cultivars presented similar yield level under no irrigation conditions; the irrigation was not sufficient to avoid yield differences between the two growing seasons; differences in rainfall were important for the crop in the dry treatment for both seasons.

Differential Metabolism of Metribuzin by Downy Brome (Bromus tectorum) and Winter Wheat (Triticum aestivum)

Weed Science ◽  
1987 ◽  
Vol 35 (6) ◽  
pp. 741-745 ◽  
Author(s):  
Daniel L. Devlin ◽  
David R. Gealy ◽  
Larry A. Morrow
Keyword(s):  
Triticum Aestivum ◽  
Winter Wheat ◽  
Bromus Tectorum ◽  
Water Soluble ◽  
Chloroform Fraction ◽  
Downy Brome ◽  
Fresh Weight ◽  
Aqueous Fraction ◽  
Root Absorption

At both 15 and 25 C, following a 24-h root absorption period, absorbed14C-metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one] was metabolized approximately 30% more rapidly to water-soluble and terminal fiber metabolites by winter wheat (Triticum aestivumL.) than by downy brome (Bromus tectorumL. # BROTE). Both species metabolized a greater proportion of metribuzin in leaf sheaths and roots than in the leaf blades. This was attributed to the increased incorporation of metribuzin into fiber. After an initial leaf extraction, metribuzin and the metabolites deaminated metribuzin (DA), deaminated diketo metribuzin (DADK), and diketo metribuzin (DK) partitioned into a chloroform fraction and five unidentified water-soluble metabolites into an aqueous fraction. At both 15 and 25 C, downy brome absorbed approximately three times more metribuzin per fresh weight than did winter wheat. The mechanism of differential tolerance of downy brome and winter wheat to metribuzin was attributed to the ability of winter wheat to metabolize metribuzin more rapidly and absorb less metribuzin than downy brome.

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