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) −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 LMXve ssels in the root by 42%, leaf area by 13%, and transpiration rate by 11%. In Gadambalias oil moisture stress did not affect RLD at depths >‐0.2 m, numbero f nodal roots, or numbero f LMXve ssels per nodal root. However, leaf area and transpiration rate were reduced by 3 and 11%, respectively. Under dry conditions, Gadambaliad isplayed a higher water extraction efficiency than Tabat throughout the profile (0‐0.9 m). In Gadambaliau, nlike Tabat, the stem was highly sclerified. A 1‐ to 3‐cell‐thick layer of schlerenchymaw as observed beneath the epidermis. The peripheral vascular bundles were surrounded with a 3‐ to 6‐ceil‐thick schlerenchyma sheath. However, in roots anatomical differences were less prominent. Drought tolerance in Gadambaliias associated with higher water extraction efficiency, fewer nodal roots per plant, fewer LMXv essels per nodal root, a smaller leaf area, and a well developed sclerenchyma.

Development and Distribution of Root System in Two GrainSorghum Cultivars Originated from Sudan under Drought Stress

“…hydraulic conductivity (Sperry et al, 2002). Salih et al (1999) reported that Gadambalia took up more water from deep soil layers despite its lower RLD than Tabat. Furthermore, Gadambalia, unlike Tabat, was not affected by drought stress in cross sectional area and capacity of late metaxylem vessels, which implied high hydraulic conductive potential of the nodal roots of Gadambalia.…”

“…These results indicated that Gadambalia extracted more water, especially from deep soil, under drought stress. Salih et al (1999) reported that Gadambalia had higher effi ciency in extracting soil water from 0-0.9 m depth than Tabat although Gadambalia had a lower RLD. The present study indicated that Gadambalia extracted more water than Tabat from deeper soil layers (Fig.…”

“…Seeds of both cultivars were provided by the Agricultural Research Corporation (ARC), Sudan. Gadambalia is a local drought-resistant cultivar, and Tabat is an improved cultivar released for irrigated cultivation (Salih et al, 1999;Tsuji et al, 2003). Root distribution in the soil profi le and rooting pattern of the axile and lateral roots were separately examined in a plastic greenhouse, under two contrasting soil water regimes (wet and dry), at the Arid Land Research Center, Tottori University, Japan.…”

Internode Characteristics of Sweet Sorghum (Sorghum bicolor (L.) Moench) during Dry and Rainy Seasons in Indonesia

“…Basal stem diameter at 50 DAS was 14.5 mm in the dry season and 74.5% of that in the rainy season. Salih et al (1999) conducted fi eld tests of sweet sorghum with irrigation totaling 700 mm and 300 mm by 50 mm in 5-day and 12-day intervals; they reported morphological differences in vascular bundles, etc. The total precipitation during the growth period of this experiment was 260 mm in the dry season and 1,190 mm in the rainy season, suggesting that different interior morphological characteristics were discernible between the two conditions.…”

“…The sweet sorghum stems, containing high concentrations of sugar, are the most important product for use as a raw material for fermentation in MSG factories. Considering the operating effi ciency of MSG factories, sweet sorghum would ideally be harvestable throughout the year, but it was reported that stem length and stem diameter are affected by the amount of irrigation (Salih et al, 1999). The sweet sorghum stem consists of internodes, similarly to other gramineous crops.…”