Showing papers by "Alexander Lux published in 1999"

Rooting, Water Uptake, and Xylem Structure Adaptation to Drought of Two Sorghum Cultivars

Abstract: Several mechanisms have been proposed to explain the high tolerance of sorghum [Sorghum bicolor (L.) Moench] to drought. This paper reports a field study on the effects of soil moisture stress on the rooting habits, transpiration rate, and xylem anatomy of two sorghum cultivars, Tabat (drought susceptible) and Gadambalia (drought tolerant). Two levels of water stress, -0.02 MPa (wet) and -0.75 MPa (dry), were applied. Tabat had a higher root length density (RLD), higher late metaxylem (LMX) vessels per nodal root, higher leaf area, and higher transpiration rate than Gadambalia. In Tabat, soil moisture stress reduced RLD by 30%, nodal roots by 31%, number of LMX vessels in the root by 42%, leaf area by 13%, and transpiration rate by 11%. In Gadambalia soil moisture stress did not affect RLD at depths ≥0.2 m, number of nodal roots, or number of LMX vessels per nodal root. However, leaf area and transpiration rate were reduced by 3 and 11%, respectively. Under dry conditions, Gadambalia displayed a higher water extraction efficiency than Tabat throughout the profile (0-0.9 m). In Gadambalia, unlike Tabat, the stem was highly sclerified. A 1- to 3-cell-thick layer of schlerenchyma was observed beneath the epidermis. The peripheral vascular bundles were surrounded with a 3- to 6-cell-thick schlerenchyma sheath. However, in roots anatomical differences were less prominent. Drought tolerance in Gadambalia is associated with higher water extraction efficiency, fewer nodal roots per plant, fewer LMX vessels per nodal root, a smaller leaf area, and a well developed sclerenchyma.

Endodermal silicification in developing seminal roots of lowland and upland cultivars of rice (Oryza sativa L.)

Abstract: Silica deposition in two upland rice cultivars, IRAT 109 and Moroberekan, and one lowland rice cultivar, Koshihikari, were compared. X-ray microanalysis coupled with environmental scanning electron...

Karwinskia Species (Buckthorn): In Vitro Culture, Micropropagation, and the Production of Toxin Anthracenone

Abstract: The genus Karwinskia (buckthorn family, Rhamnaceae) was named after the Bavarian botanist Wilhelm Frederick von Karwinski, who collected plant material for herbaria in Mexico in the first half of the last century. Medicinal use of some species of this family, mainly Rhamnus spp. and Frangula spp., are well known in Europe, some of them being used since Ancient Greek times, or even earlier.