Effects of Localized and Overall Water Stress on Assimilate Partitioning in Barley Between Shoots, Roots and Root Exudates

Abstract

SUMMARY Polyethylene glycol 4000 (PEG) at an osmotic potential of −0.3 MPa had no effect on uptake of 14CO2 and partitioning between shoots and roots in barley. When an osmotic potential of −0.8 MPa was applied to the upper zone of the root system, total 14CO2 uptake and partitioning were unaffected but assimilate accumulated in the tips of nodal roots exposed to PEG. There was a parallel accumulation of soluble sugars. Transport of assimilates to the seminal root system declined. Exudation of soluble, labelled compounds by the roots was markedly diminished. When PEG was supplied to the upper root zone at −0.8 MPa and the lower zone at −0.6 MPa total 14CO2 uptake and assimilate transport declined, but there was still some accumulation of labelled compounds and soluble sugars in the nodal root tips and root exudation was diminished. The results are discussed in relation to assimilate partitioning, growth and osmotic adjustment in nodal roots.

Role of water stress in differential aluminum tolerance of two barley cultivars grown in an acid soil

“…These findings are consistent with results reported for barley by other workers (1,2,4,9,11,27,35,37,38). Growth differences between the two cultivars were greatest when high Al stress and high water stress were combined.…”

“…The influence of water stress on root/shoot ratio has been examined by various investigators (15,17,23,36,37). In a review of 28 articles, Gales (15) found that drought increased root/shoot ratio in 19 cases, lowered it in four, had no effect in three and was variable in two.…”

Atmospheric CO2 enrichment and drought stress modify root exudation of barley

“…Similarly, Shone et al . () found higher K levels in root extracts of barley seedlings grown in nutrient solution with an osmoticum creating drought stress.…”

“…Cytokinins are known to promote movement of nutrients (Taiz & Zeiger, 2002). Similarly, Shone et al (1983) found higher K levels in root extracts of barley seedlings grown in nutrient solution with an osmoticum creating drought stress.…”

Drought stress condition increases root to shoot ratio via alteration of carbohydrate partitioning and enzymatic activity in rice seedlings

“…In contrast to an increase in R/S under drought, low humidity stress increases dry matter partitioning to shoots in rice (Hirai et al 1994). Additionally, previous studies also observed that DS had no effect on assimilate partitioning between roots and shoots (Shone et al 1983;Asch et al 2005). Collectively, these observations suggest that response of assimilate distribution and R/S to drought stress is different, depending on genotype, degree and duration of drought stress, rate of stress development, or the synergistic/antagonistic interaction of these factors.…”