Plant building material Thousands of glucose molecules can be linked together to form the complex carbohydrate cellulose. Production of other types of food Glucose is an example of a carbohydrate - it contains the chemical elements carbon, hydrogen and oxygen.
Higher Subjects Higher Subjects up. This is the reason why, after a few seconds of chewing, a piece of relatively tasteless bread develops a certain sweet taste. This hydrolysis by amylase continues all the way to the stomach, then the m altase present in the small intestine splits the maltose molecules into two glucose molecules and completes the hydrolysis. The glucose is then actively absorbed by the cells of the intestine and enters the bloodstream.
When it arrives in the liver, part of it is used to synthesise glycogen, an energy reserve in the form of a polysaccharide made up of tens of thousands of glucose units. This glycogen can then be converted back into glucose released into the bloodstream as and when the body needs it. This mechanism determines the level of glucose in the blood and is carefully controlled by two hormones, insulin and glucagon. These hormones inform the cells if they need to store or release glucose into the bloodstream to enable the body to function properly.
The concentration of glucose in the blood plasma is called glycaemia. In a healthy person, blood glucose concentration is between 0. Glucides Vevey. Home Glucose. Glucose was then added at concentrations of 0, 1. The seedlings were cultured as described for 15 d with sufficient nutrient supply, after which shoots and roots were harvested separately.
The roots were washed in 50 mM CaCl 2 in an ultrasonic bath for 1 min and then washed three more times in purified water. The N content was determined in six replicates from each treatment using the Micro-Kjeldahl method. Seventy-two similar seedlings were pre-cultivated for 15 d, after which the roots and centrifuge tubes were washed with sterilised purified water.
The seedlings were cultivated in 1 mM Three seedlings were pooled to account for variation between plants in each treatment, and each treatment was replicated three times. The roots were washed and the shoots and roots were freeze-dried separately and ground into a powder as described above. This control design was the same in Experiments 2 and 3 as well. The variation in the growth between the different treatments can affect the natural 15 N abundance in tissues; therefore, we detected N content for each treatment, and three seedlings were pooled and treated as one replicate.
Pakchoi was pre-cultivated as described in Experiment 1 for 6 d, and 81 similar seedlings were selected. The shoots and roots were harvested separately and three seedlings were pooled into a single sample. The samples were washed, dried, ground, and the 15 N content was detected as described in Experiment 1. Pakchoi seedlings were pre-cultivated for 25 d and similar seedlings were selected. The glucose concentration in this experiment was determined based on the N source. The optimal glucose concentration for pakchoi growth was 4.
Therefore, 45 seedlings were cultivated in 1 mM Simultaneously, the protonophore carbonyl cyanide m-chlorophenylhydrazone CCCP [ 30 ], that inhibits the active uptake of glycine was used to examine the effect of glucose on the active and passive uptake of glycine. The uptake tests for CCCP-treated and untreated specimens were conducted simultaneously with three replicates per treatment. The roots and shoots were harvested separately and five seedlings were pooled as one sample for each experimental replicate.
The roots were washed, dried, and analysed as described in Experiment 1. The 15 N values obtained from CCCP-treated samples represented the passive uptake of glycine in pakchoi. After root N uptake, several enzymes metabolise glycine; is the metabolism of glycine changed by the uptake of glycine? Ninety-six seedlings were pre-cultured for 22 d and then starved overnight as previously described in Experiment 3.
Forty-eight seedlings were cultivated for 4 d in 1 mM glycine in glucose concentrations of 0, 4. The nutrient solution was changed every 2 d.
The seedlings were harvested and six seedlings were pooled to represent one sample in each of the four experimental replicates.
The activities of glutamine synthetase GS [ 31 ], glutamic-pyruvic transaminase GPT , and glutamic oxaloacetic transaminase GOT [ 32 ] were measured in roots and shoots. Pakchoi seedlings were pre-cultured for 25 d and the 72 uniform seedlings were washed and N-starved overnight. The shoots and roots were harvested separately and the roots were washed as described in Experiment 1. The experiment included six replicates with four seedlings in each replicate to reduce individual plant variation.
Amino acid content was measured with an automatic amino-acid analyzer L, Hitachi, Japan. Pakchoi seedlings were pre-cultured for 25 d and 96 similar seedlings were selected for further cultivation. The roots were washed several times with purified water and the seedlings were N-starved for 12 h. The pakchoi roots and shoots were harvested separately; eight seedlings per treatment were pooled and each treatment had 6 replicates.
The roots were washed, dried, and ball milled as previously described. The 15 N-labelled amino acids were detected by gas chromatography—mass spectrometry GC-MS as previously described [ 15 ] with minor modifications. The extraction and centrifugation of these samples was repeated once more.
The cation exchange columns were washed with 20 ml ultrapure water, and 20 ml of 4 M ammonia solution was used to wash out the amino acids. The proportion of total N taken up from different sources was calculated using the following equation:. All statistical analyses were performed using SAS 8. Figures were created using Origin 8. When glycine was supplied as the sole source of N, the optimal glucose concentration for pakchoi growth and 15 N-glycine uptake was 4. These results indicate a preferential increase in pakchoi N-assimilation and growth in the presence of low levels of glucose.
Pakchoi biomass and N uptake under different glucose concentrations. Experiment 1 showed that glucose had a significant effect on the growth and N uptake in pakchoi, but how do different levels of glucose affect the uptake of glycine, nitrate, and ammonium? Externally supplied glucose had a significant effect on the relative uptake of N from mixed N sources Fig.
The uptake and contribution of 15 N-ammonium to the overall N uptake was highest in the absence of glucose. These results are evidence that glucose can alter N uptake from preferred nitrogen sources, providing a potential tool for supporting amino acid supplementation in pakchoi cultivation.
Furthermore, the N contribution from glycine in the shoots and roots of plants grown in the three glucose levels was Effects of glucose on 15 N uptake under mixed N source conditions. The uptake of glycine, nitrate, and ammonia in a shoots and c roots. Glucose changed the uptake and N contribution of glycine whether in single or mixed N sources Experiment 1 and 2 , but was this great difference was caused by root uptake?
In roots, glucose had a significant effect on only the active uptake of glycine under both mixed N and single N source conditions Fig. Under single N source conditions, the active uptake of 15 N-glycine in the roots at the optimal glucose concentration 4. Moreover, in mixed N source conditions, the uptake of 15 N-glycine with the high glucose concentration was Effects of glucose on the short-term uptake of glycine- 15 N.
The Glycine- 15 N uptake was measured in a shoots and b roots in single N glycine source conditions, and in c shoots and d roots in mixed N conditions. Under mixed N source conditions, the N contribution of glycine decreased under high glucose level in the long-term N uptake test Experiment 2 , but the glycine short-term N uptake amount in high glucose conditions was similar with the optimal glucose level, which prompts the question of whether glycine metabolism inhibits the N contribution of glycine rather than root uptake under high glucose level.
Using glycine as a single N source identified no significant differences in the activities of GPT, GOT, and GS in the roots between plants that received the optimal or high glucose treatments Table 1. However, when supplied with mixed N sources, the GS activity in the shoots and roots were significantly lower at high glucose concentrations than at the optimal glucose concentrations.
The content of amino acids and ammonia in pakchoi were significantly affected by a 12 h glucose treatment Fig. While the content of total amino acids in shoots showed little difference in optimal and high glucose treatment levels, it was significantly higher in roots of plants that were supplemented with the optimal glucose concentration compared to that of the high glucose treatment. In addition, the content of glycine in roots treated with the high glucose concentration was much higher, and the content of serine was significantly lower than that of plants treated with the optimal glucose concentration, respectively.
Experiment 5 shows that glycine root content in high glucose was higher than in the glucose optimal level; serine was much lower under the same glucose conditions, indicating that the metabolism of glycine compared to serine inhibited the N contribution of glycine at high glucose levels. However, the data collected by the amino-acid analyser has two disadvantages: 1 the amino-acid analyser cannot detect asparagine and glutamine, which are important in glycine metabolism; and 2 whether the detected amino acids are from root uptake of glycine or from the metabolism of nitrate and ammonium cannot be determined.
To explore the effect of high glucose levels on the metabolism of glycine, 15 N labelling and GC-MS were used to detect the 15 N-labelled amino acids in the pakchoi shoots and roots. Glucose treatment had a significant effect on the 15 N-labelled amino acid content in pakchoi Fig. The 15 N-amino acids varied greatly between shoots and roots. In roots the main 15 N-labelled amino acids were glycine, serine, glutamine, and glutamic acid; in shoots, the major labelled amino acids were glutamine, glutamic acid, asparagine, and gamma-aminobutyric acid.
In roots, 15 N-glycine was significantly higher in plants cultivated in the high glucose treatment, while serine, gamma-aminobutyric acid, and asparagine levels were significantly lower than those measured in plants treated with the optimal glucose concentration Fig. In shoots, asparagine, glutamic acid, and glutamine were significantly higher in the optimal glucose treatment than in the high glucose concentrations Fig. The results of this study indicate that relatively low concentrations of glucose accelerated pakchoi growth, while excessive glucose levels retarded both growth and N accumulation Fig.
A previous study showed that high glucose in plants reduced the rates of photosynthesis and sugar transport, and low glucose in plants led to increased sugar transport activities [ 34 ].
In our study, we found that glucose levels alter N uptake, indicating that its regulation is another example of how glucose affects pakchoi growth. This result indicates that the effect of glucose on pakchoi growth is related to the N supply. Similarly, nitrate levels affected the glucose sensitivity of wild-type Arabidopsis during germination [ 35 ].
This large discrepancy may be caused by differences between the plant species and the glucose availability dissolved in water versus that in agar. Plants possess the ability to take up sugars, which can regulate plant growth and N uptake. Massive amounts of sugar were detected in the xylem sap, which indicated that the glucose in roots might be acropetally transported to the shoots and leaves [ 37 , 38 ].
Glucose is not only regarded as an energy and carbon resource for biomass production, but it also acts as a rapid molecular signal to coordinate root and shoot development [ 37 ]. We show that the optimal concentrations of glucose 4. Karen Gardner is a freelance writer and editor based in Maryland.
She has more than 20 years of experience writing and editing health, home and gardening stories. Without glucose, plants won't grow or reproduce. Ideal Conditions for Photosynthesis.
What is Glucose Made Of? When Does Respiration Occur in Plants? Six Basic Parts of a Plant. Why Do Plants Need the Sun? The Effect of Darkness on Photosynthesis. What Are Light Dependent Reactions? Importance of Pigments in Photosynthesis. Solar Energy Facts for Kids.
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