## 4 Discussion  
In the presented paper, the PAS staining technique was coupled with HRGC for the precise measurement and profiling of individual monosaccharides, oligosaccharides, and polysaccharides. This integration clarified the complex carbohydrate changes induced by Cd stress, including changes in the sugar content, starch accumulation, and the dynamics of specific carbohydrate compounds, such as galactinol and raffinose. The experiment was conducted 1, 7, and 28 days after the treatment with Cd on pea plants during the transition from the vegetative phase to the generative phase of plant development. During this transition, plants undergo significant changes in their growth and development, shifting from producing leaves and stems to producing flowers and fruits. Our previous studies showed that after the fourth week of growth, pea plants start to produce flowers [14]. The present study confirmed the inhibitory effect of Cd on seed production when plants were treated with 50, 100, and 200 uM CdSO4. As described in Section 3, these plants had accumulated 11.35, 23.68, and 34.57 ug/g of Cd in the DW of the shoots and 73.50, 208.89, and 317.68 ug/g of Cd in the DW of the roots, respectively. This confirms the results of previous studies suggesting most plants show visible symptoms of Cd toxicity when the Cd concentration in the plant tissue reaches 3 to 30 mg/kg, the total Cd concentration in the soil exceeds 8 mg/kg, or the bioavailable Cd concentration becomes >0.001 mg/kg [48]. Furthermore, both the results of Cd concentration and TF (TF < 1) showed that the majority of Cd absorbed by pea plants was stored in the root system. Consistent with prior research, our findings support the classification of pea plants as excluder plants [6]. This suggests that pea plants exhibit a strategy for the accumulation of Cd within the roots or to inhibit the translocation of Cd to the above-ground parts. Interestingly, the analysis of the TI showed that the Cd stress does not have a significant impact on the biomass production of pea plants. However, as previously confirmed, Cd influences the vegetative stage of development by increasing the number of internodes per shoot length and by disturbing the root growth but also affects the transition from the vegetative to the generative stage of the development of pea plants [14]. The present study focused on the effect of Cd on the starch distribution and soluble carbohydrates concentration after 1, 7, and 28 days of Cd treatment in pea plants. Furthermore, we analysed soluble carbohydrates in the seeds and pots of control plants and plants treated with 10 uM CdSO4. We showed that Cd stress had a great impact on starch distribution patterns in leaves and stems. The PAS reaction, which is based on the oxidation of carbohydrates by periodic acid followed by their subsequent reaction with Schiff reagents, allows for the visualisation and quantification of polysaccharides such as starch and cellulose in plants during development or stress [40; 49]. To the best of our knowledge, this is the first study of Cd-induced alterations in PAS-positive deposits in higher plants (_P. sativum_ leaves and stems). However, this method was used for the analysis of Cd's effect on apical segments of _Hypnea musiformis_[37] and young gametophytes of _Gelidium floridanum_[38]. Similarly to [PERSON] et al. [37], we observed accumulation of starch grains in the leaves of control and Cd-treated plants and also in the stems of the control and 50 uM Cd-treated plants after 1 week of the treatment. Moreover, the increased number of starch grains was observed in young leaves of control and 50 uM CdSO4-treated plants 4 weeks after Cd treatment. However, it is important to notice the differences in the starch accumulation in the stems between control and Cd-treated plants after 4 weeks of Cd treatment. This characteristic accumulation of starch in the stems may suggest the disturbance of the translocation of carbon from the stems to flowers and then fruits since these plants did not produce seeds.