Sugar Uptake and Translocation in the Castor Bean Seedling II. Sugar Transformations During Uptake.
نویسندگان
چکیده
During sucrose uptake by the cotyledons of castor bean seedlings excised from their endosperms, small amounts of glucose and fructose accumulate in the medium. When these hexoses were supplied separately, it was found that the rate of fructose uptake exceeded that of glucose at concentrations up to 0.5 m. Sucrose uptake exceeded that of both hexoses combined, particularly at concentrations greater than 0.1 m. Only minute amounts of labeled hexoses were recovered from the cotyledons after exposure to glucose-U-(14)C or fructose-U-(14)C; sucrose contained virtually all of the (14)C in the sugar fraction. The fructose and glucose moieties of the extracted sucrose were equally labeled when glucose-U-(14)C was supplied, and the glucose moiety contained 41% of the (14)C when fructose-U-(14)C was the substrate.Several considerations led to the conclusion that by far the greater part of sucrose absorbed by the cotyledons was not hydrolyzed prior to or during uptake. These included the differential responses of hydrolysis and uptake to pH, and to Tris(hydroxymethyl) aminomethane, the absence of interference of the hexoses on sucrose absorption and particularly the demonstration that when the cotyledons were supplied with fructosyl-(14)C sucrose, 90% of the (14)C was retained in the fructose residue of sucrose in the cotyledons.
منابع مشابه
Sugar Uptake and Translocation in the Castor Bean Seedling I. Characteristics of Transfer in Intact and Excised Seedlings'
sugar present in the endosperm was predominantly, and in the cotyledon almost exclusively, sucrose. Anatomical features were described which contribute to the efficiency of the cotyledons as organs of absorption and transmittal of sucrose to the embryonic axis, where hexoses are much more prevalent. The ability of the cotyledons to absorb sucrose survived removal of the endosperm from the seedl...
متن کاملSucrose synthesis from acetate in the germinating castor bean: kinetics and pathway.
During the germination of fatty seeds such as the castor bean, a rapid conversion of fat to sugar occurs (2). The fatty acids are probably broken down to acetyl units via P-oxidation (3) ; the discovery of the glyoxylate cycle enzymes (4) in the castor bean endosperm (5) provided a mechanism whereby these acetyl units could be quantitatively converted to malate. Since malate could be viewed as ...
متن کاملMonitoring sugar beet rooting depth irrigated with recycled waste water and different irrigation methods for water savings in an arid climate
ABSTRACT- A detailed understanding of crop rooting systems will facilitate water use reduction, optimized nutrient uptake and irrigation scheduling more efficiently. A field experiment was conducted during 2005-2006 to investigate sugar beet rooting depth growth, irrigated with three irrigation methods (subsurface drip, surface drip and furrow) and two water qualities (recycled wastewater: EC= ...
متن کاملInfluence of Different NO3/NH4 on Nitrate and Ammonium Uptake Kinetics of Sugar Beet (Beta vulgaris L.) Seedlings
Solution culture experiments were carried out to study the kinetics at cotyledon stage (11-day-old) and the effect of different NO3/NH4 on NO3 and NH4 uptake at seedling stage (31-day-old) with two cultivars of sugar beet, including Tianyan7 and Tianyan8. NO3 uptake by sugar beet seedlings at cotyledon stage (11-day-old) reached equilibration after 2 hours of adaptation, and NH4 uptake reached ...
متن کاملتغییر ویژگیهای کیفی و سینتیک افت قندهای احیاکننده در خلال سیبزمینی طی آنزیمبری
Due to problems in storage, transportation and price fluctuation of fresh potato, production of ready-to-use products like French fries is of particular importance. French fries quality mainly depends on the appearance, taste, color, texture and oil uptake. One of the important steps in product processing is blanching. This step improves product texture and color due to the decrease in reducing...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
- Plant physiology
دوره 42 2 شماره
صفحات -
تاریخ انتشار 1967