Contribution of Sugars to Osmotic Adjustment in Elongating and Expanded Zones of Wheat Leaves During Moderate Water Deficits at Two Light Levels

Abstract

Water was withheld from wheat seedlings grown at two light levels, so that the soil water content was reduced by 50% and the leaf water potential of treated plants was about 0.5 MPa below that of controls. Growth was initially reduced but recovered after about 4 days of the water deficit treatment. Osmotic adjustment (calculated as the difference between the osmotic potential at 100% relative water content of the treated and controls plants) occurred in both the elongating and expanded zones of leaves. In plants grown at a very high irradiance, an increase in sugars accounted for 70-100% of the osmotic adjustment of 0.12-0.34 MPa in the elongating and expanded zones of leaves sampled both at dawn and at midday. The increased amounts of sugars were approximately equivalent to the decreased consumption of carbohydrate during the initial reduction in growth. Glucose was the main component of the increase in sugars in the elongating regions, while sucrose was more important in the expanded laminae. During the morning, sugars increased to similar extents in controls and treated plants. In plants grown at a moderate irradiance, sugars did not account for the osmotic adjustment of 0.10-0.21 MPa in the expanded laminae at dawn or at midday. At dawn, sugars were much lower in treated than in control plants but, during the morning, sugars accumulated more in the treated plants and sugar levels of the two groups at midday were similar. In contrast, sugar levels in the youngest elongating leaf of the treated plants were the same as in the controls at dawn, and were double those in the controls at midday.

Reduced light and moderate water deficiency sustain nitrogen assimilation and sucrose degradation at low temperature in durum wheat

“…NL also enhanced the activity of invertase in MvTD10-10 under both water regimes, which reflects its light dependency. A higher level of sucrose hydrolysis was also found in water-stressed wheat plants under NL (Munns and Weir, 1981). In this connection, it seems that both mild water deficiency and NL are able to compensate for the reducing effect of cold on sugar remobilisation in these durum cultivars via the higher activity of invertase.…”

The effect of salinity stress on ions and soluble sugars distribution in leaves, leaf sheaths and roots of rice (Oryza sativa L.) seedlings

“…Kerepsi and Galiba (2000) reported that carbohydrates changes are important because of their relationship with such physiological processes as photosynthesis, translocation and respiration. Some studies reported that plants sugars content rose (Munns and Weir 1981) or remained constant (Morgan 1992) under salinity.…”

Accumulation and consumption of solutes in swards of Lolium perenne during drought and after rewatering

“…Drossopoulos, Karamanos & Niavis (1987) compared irrigated and rainfed wheat and found that sucrose accumulated in laminae under stress whereas monosaccharide contents were low and unaffected. On the other hand, Munns & Weir (1981) exposed pot-grown wheat plants to moderate water stress over periods of several days and found that glucose was the predominant sugar in the leaves, and accumulated most rapidly during drought. Riazi, Matsuda & Arslan (1985) described yet another pattern of response when barley seedlings were exposed to brief (up to 7 h) osmotic stress: sucrose contents decreased and glucose increased.…”