scholarly journals Effect of Heat Stress on Enzymes that Affect Sucrose Levels in Potato Shoots

1996 ◽  
Vol 121 (6) ◽  
pp. 1152-1156 ◽  
Author(s):  
James H. Lorenzen ◽  
Abbas M. Lafta
Keyword(s):  
Heat Stress ◽  
Sucrose Synthase ◽  
Sucrose Phosphate Synthase ◽  
Sink Strength ◽  
Mature Leaves ◽  
Neutral Invertase ◽  
Young Leaves ◽  
Genotype Interaction ◽  
Activity Of Enzymes ◽  
Sucrose Phosphate

Potato (Solanum tuberosum L.) responds to heat stress with a shift in partitioning from tubers to shoots. Enzymes responsible for sucrolysis previously have been used as indicators of sink strength and are likely involved in controlling flow of carbon into developing organs. Changes in activity of enzymes involved in sucrose metabolism were investigated in shoots of two potato cultivars that previously were characterized as susceptible and tolerant to heat stress. Enzyme activity of sucrose synthase (SS) and invertases was determined for mature leaves, young leaves, and stems of plants adapted to 21/19 °C, or after transferring plants to 29/27 °C for 3 days. High temperatures resulted in a nonsignificant increase in activities of SS, acid, and neutral invertase in young growing leaves but not in stems or mature leaves. The combined activity of the two invertases was ≈40 times higher than SS activity in young leaves. There was no temperature genotype interaction with regard to these enzymes in the tissues investigated. A previously reported increase in activity of sucrose-phosphate synthase in mature leaves of plants subjected to high temperature was reversed after these plants were returned to a normal growing temperature.

scholarly journals Seasonal Fluctuations of Some Enzymes Relating to Sucrose and Sorbitol Metabolism in Peach Fruit

1990 ◽  
Vol 115 (2) ◽  
pp. 278-281 ◽  
Author(s):  
Takaya Moriguchi ◽  
Tetsuro Sanada ◽  
Shohei Yamaki
Keyword(s):  
Sucrose Synthase ◽  
Prunus Persica ◽  
Early Stage ◽  
Sucrose Phosphate Synthase ◽  
Acid Invertase ◽  
Peach Fruit ◽  
Development Activity ◽  
Stage Of Development ◽  
Sugar Levels ◽  
Sucrose Phosphate

Sugar levels and composition were determined in developing `Hakuto' peach (Prunus persica Batsch var. vulgaris Maxim.) fruit. Glucose and fructose in nearly equal amounts were the predominant sugars detected during the early stage of development. Sucrose subsequently began to accumulate and was the predominant sugar in mature fruit. Sorbitol remained at a low level throughout development. The large increase in the amount of sucrose was accompanied by a rapid increase in sucrose synthase (EC 2.4.1.13) activity. Sucrose phosphate synthase (EC 2.4.1.14) was also detected in flesh extracts, but the activities were low throughout development. Acid invertase (EC 3.2.1.26) activity was highest in young fruit and declined with development. Activity, however, increased again at a later stage of development. Peach fruit contained appreciable sorbitol oxidase activity, while other sorbitol-related enzymes were barely detectable, suggesting that transported sorbitol was predominantly converted to glucose. These results suggest that the supply of glucose and fructose depends on acid invertase and sorbitol oxidase, and that accumulation of sucrose depends on-sucrose synthase.

Carbohydrate Storage and Mobilisation by the Culm of Wheat Between Heading and Grain Maturity: the Relation to Sucrose Synthase and Sucrose-Phosphate Synthase

1994 ◽  
Vol 21 (3) ◽  
pp. 255 ◽  
Author(s):  
IF Wardlaw ◽  
J Willenbrink
Keyword(s):  
Sucrose Synthase ◽  
Flag Leaf ◽  
Sucrose Phosphate Synthase ◽  
Leaf Sheath ◽  
Water Soluble ◽  
Soluble Carbohydrates ◽  
Carbohydrate Storage ◽  
Stem Reserves ◽  
Sucrose Phosphate ◽  
Phosphate Synthase

Wheat plants grown under non-stress conditions at a dayhight temperature of 18/13�C under glasshouse conditions from head emergence to maturity showed a maximum accumulation of water-soluble, non-structural carbohydrates 20-25 days after anthesis. This storage was largely as fructans with the timing and amount of storage and mobilisation varying between cultivars, although the maximum concentration (fructose equivalents per unit stem fresh weight) was similar in all cultivars. The main storage in the culm was located in the lower part of the peduncle enclosed by the flag leaf sheath, in the penultimate internode and for one cultivar also in the flag leaf sheath. 14CO2 pulse-chase studies showed that there was a considerable delay in the incorporation of flag leaf assimilates into stem fructans, a delay probably associated with transfer and metabolic processes in the stem itself. At anthesis, when soluble carbohydrates were rapidly accumulating in the culm, the level of activity of sucrose synthase (SS) in the penultimate internode was much greater than that of sucrose phosphate synthase (SPS). The activity of SS declined rapidly as active storage ceased. This pattern was the reverse of that found in the leaf where SPS, rather than SS, was initially high and declined towards maturity. These changes are discussed in relation to the possible role of sucrose synthesising enzymes, particularly SS, in the accumulation and mobilisation of stem reserves in wheat.

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