## 4 Discussion
It was shown that the starch is required for pollen maturation [50]. [PERSON] and [PERSON] [51] showed no definitive pattern of changes in the starch content in the two rice cultivars, while [PERSON] and [PERSON] [30] showed a significant accumulation of starch in three rice cultivars after Cd treatment. Moreover, Cd-induced starch accumulation was also observed in the common reed [52], _Phylanthus amarus_[53], and _Lemma minor_[54]. [PERSON] et al. [52] proposed that the common reed may preferentially allocate absorbed carbon as the carbon source for the synthesis of Cd and \(\alpha\)-glucan complexes in its stem, followed by the suppression of Cd transfer to the leaves, which operate as the photosynthetic organ. These responses may allow the common reed to grow successfully even in conditions of severe Cd stress. Starch-sugar interconversion in source and sink tissues plays a substantial physiological role in all plants [24]. The presented results confirmed that the inhibitory effect of Cd stress may be caused by energy allocation. During abiotic stress, plants prioritise energy allocation towards stress response mechanisms rather than reproductive processes [55]. These results and our previous study [14] showed that 50, 100, and 200 \(\upmu\)M Cd-treated plants do not produce seeds. This indicates that the shift in resource allocation can affect the supply of sugars to develop flowers and seeds, potentially impacting the seed development and yield. The accumulation of starch in the stems and changes in soluble carbohydrates in Cd-treated plants suggest that the impact of Cd is critical for the transport of sugars from leaves to flowers and the development of seeds. Cd-induced accumulation or steady concentrations of fructose, glucose, _myo_-inositol, sucrose, and maltose were observed in plants 4 weeks after Cd treatment at concentrations greater than 50 \(\upmu\)M CdSO\({}_{4}\), while in control plants and plants treated with 10 \(\upmu\)M CdSO\({}_{4}\), they decreased. This can be a confirmation that, in plants producing flowers and pods, soluble sugars are transferred to the flowers/fruits. The effect of sugar on vegetative development and floral transition has been discussed [56; 57; 58]. Previous studies showed Cd-induced increases in the levels of soluble and reducing carbohydrates [31; 59] or a decrease in the content of reducing sugars [20; 60]. Analysis of the Cd effect on maize varieties suggests that sucrose metabolism may be a secondary Cd response, and that the Cd-sensitive variety used more carbohydrates to defend against Cd stress rather than to support the growth of the Cd-tolerant variety [59]. Moreover, similar to the presented results, the effect of Cd and the accumulation of sucrose or fructose changed during the Cd treatment [61]. [PERSON] et al. [61] also suggested that changes in the sucrose metabolism were induced to maintain the osmotic balance in damaged cells and to protect the plant from Cd stress. The decrease in the water content is described as one of the effects of Cd stress on plants [60; 62]. Interestingly, the Cd-induced accumulation of galactinol in the shoots and raffinose in the shoots and raffinose in the shoots and roots was also observed. Raffinose accumulation after Cd treatment was first noted by [PERSON] and [PERSON] [26] in in vitro cultured _Lupinus albus_. [PERSON] et al. [32] also observed an increased level of raffinose in two-week-old _Arabidopsis thaliana_ seedlings after exposure to Cd. Since then, similarly to our results, Cd-induced expression of genes encoding galactinol synthase (GolS) and raffinose synthase (RS) has also been noted in rice [63]. The involvement of the galactinol synthase gene (_GolS_) in heavy metal stress was reported recently by [PERSON] et al. [64]. There are numerous data showing stress-induced expression of _GolS_ and/or _RS_. Induction of the expression of the _PsGolS_ and _PsRS_ genes during dehydration and osmotic stress in pea seedlings was also observed [44; 65]. Moreover, [PERSON] et al.