**2.3 Effects of drought on influence on photosynthetic pigments synthesis**

The content analysis of chlorophylls and carotenoids in the amaranth leaves showed that some changes were associated with drought (**Figure 4**). An increase of Chl a, b and Car was observed in the leaves of drought-affected amaranth species. In the leaves of *A. tricolor* L. cv. Valentina, the content of Chl a doubled; on the other hand, a slight decrease in the content of Chl b was noted. In the leaves of *A. cruentus* L. cv. Krepysh, the content of Chl b increased slightly in comparison with the content of Chl a. The content of carotenoids in the amaranth leaves increased in the conditions of

#### **Figure 2.**

*The protrusions of crystals (a) and Mineral inclusions in the cross-section leaves* Amaranthus tricolor *cv. Valentina.*

*Metabolite Profile of* Amaranthus tricolor *L. and* Amaranthus cruentus *L.… DOI: http://dx.doi.org/10.5772/intechopen.102375*

**Figure 3.**

*Mineral inclusions in the cross section of amaranth leaves and EDS crystal alalysis. SEM micrographs and corresponding EDX spectra of elements in the cross-section leaves* Amaranthus tricolor *cv. Valentina., sample 2000 X. The energy spectrum of the X-rays character emitted from the element of K, P and Ca.*

moisture deficiency: in the leaves of *A. tricolor* L., it increased 2.5 times, and in the leaves of *A. cruentus* L.—1.5–2.0 times compared with the control. These results are consistent with the data received from the testing on Choy sum in the dry season [25], which reported an increase in total carotenoid content under drought stress.

A high correlation was found between Chl a and Car (r = 0.985) and Chl b and Car (r = 0.977) in the leaves of *A. tricolor* L. and *A. cruentus* L., respectively. The observed changes in photosynthetic pigments of the leaves in drought are probably associated with free-radical-induced oxidation of Chl pigment [26], the destruction of some chloroplasts, and an increase in the activity of Chl catabolizing enzyme of chlorophyllase [27]. The increase in chlorophyll concentration under drought stress can be determined as an indicator of the plant tissues' resistance to abiotic stress under the drought conditions, which is fully consistent with the data of Jain et al., [28], who reported similar observations. Carotenoids are involved in drought stress resistance due to their ability to capture singlet oxygen. They can also inhibit lipid peroxidation

#### **Figure 4.**

*The content of chlorophyll* a *(Cla), chlorophyll* b *(Clb) and carotenoids (Car) in the leaves of amaranth (C4) under stress conditions of drought. Data are the mean SE of three replicates.*

and superoxide formation by dehydrating factors. Carotenoids and beta-carotene may play the main protective role in photosynthetic tissue as they directly help plants resist drought [29].
