Anatomical adaptations of Astragalus gombiformis Pomel. under drought stress

Abstract

The present study was designed to study the effect of drought on root, stem and leaf anatomy of Astragalus gombiformis Pomel. Several root, stem and leaf anatomical parameters (cross section diameter, cortex, root cortical cells, pith, leaf lamina and mesophyll thickness) were reduced under moderate to severe water deficit (20–30 days of withheld irrigation). The stele/cross section root ratio increased under moderate water deficit. The root’s and stems vascular systems showed reduced xylem vessel diameter and increased wall thickness under water deficit. In addition, the root xylem vessel density was increased in these drought conditions while it was unchanged in the stems. The stomata density was increased under prolonged drought conditions whereas the stomata size was untouched. The leaf vascular system showed reduced xylem and phloem tissue thickness in the main vein under moderate to severe water deficit. However, in the lamina the vascular tissue and the distance between vascular bundle were unaffected. Our findings suggest a complex network of anatomical adaptations such as a reduced vessel size with increased wall thickness, lesser cortical and mesophyll parenchyma formation and increased stomata density. These proprieties are required for the maintenance of water potential and energy storage under water stress which can improve the resistance of A. gombiformis to survive in arid areas.

Exogenously applied glycinebetaine induced alteration in some key physio-biochemical attributes and plant anatomical features in water stressed oat (Avena sativa L.) plants

“…They found that root length and number of secondary roots decreased, while number of medullary rays and vascular region increased under water deficit conditions. Boughalleb et al (2014) found that anatomical variations such as reduced vessel size, mesophyll thickness, and cortical parenchyma development were observed in Astragalus gombiformis under water stress conditions for the maintenance of energy storage and improved resistance for survival of the plants in dry areas. Vasellati et al (2001) reported that under water deficit conditions, diameter of root and metaxylem area decreased in Paspalum dilatatum, thereby lowering the risk of embolism, increasing the water-flow resistance and number of root hairs, which could increase the water uptake ability in the plant.…”

“…ecotypes. It is believed that anatomical modifications such as reduced vessel size, mesophyll, and cortical parenchyma formation are essential to survive under water deficit conditions (Boughalleb et al, 2014).…”

The Contribution of Calcium to Changes in Leaf Anatomical Character of Oil Palm Seedlings (Elaeis guineensis Jacq.) under Drought Stress

“…The changes in the lower epidermal cell length were seen in Astragalus gombiformis Pomel. under moderate drought stress (20 days) and severe drought stress (30 days) (Boughalleb et al, 2014). The decreasing of the size of leaf epidermal exposed to drought stress was an effect of decreasing water availability in the growing media so that the water needed for full cell turgor was not available.…”

“…The mesophyll thickness of Astragalus gombiformis Pomel. decreased significantly when exposed to moderate and severe drought stress ( 20-30 days) (Boughalleb et al, 2014). This is a leaf mechanism allowing CO2 to enter the chloroplast in the palisade tissue at the time of the opening of the reduced stomata and a plant strategy to protect photosynthesis when the plant is exposed by drought stress.…”

Effects of Combined High Temperature and Waterlogging Stress at Booting Stage on Root Anatomy of Rice (Oryza sativa L.)

“…This is mainly due to the fact that the root cortex hinders water transport via the roots. Therefore, the thicker the root cortex, the greater the resistance to water transport and the smaller the rate of water absorption (Wang et al, 2005;Boughalleb et al, 2014;Enstone et al, 2002;Miyamoto et al, 2001). However, the root diameter, stele diameter, and thickness of the outer root layer under high temperature and waterlogging stress showed no significant differences with those of the CK, which was attributed to different rhizosphere temperatures.…”