Ultrastructure of Leaf Mesophyll Cells of Alyssum desertorum L. under Soil Flooding

For the first time, the effect of 5- and 10-day soil flooding on the ultrastructure of the leaf mesophyll cells of the psammophyte desert madwort (Alyssum desertorum L.) was investigated. The seeds for the experiments were collected from plants of dry sandy areas of the gully slopes of the ravine forest in the steppe zone of the Dnipropetrovsk oblast. It is shown that a characteristic feature of the leaf photosynthetic cells of this species is the presence of single and large, up to 6 pm, peroxisomes, which are in close contact with chloroplasts and mitochondria, playing a key role in photorespiration. The general organization of palisade parenchyma cells on days 5 and 10 of soil flooding is similar to that in the control. A slight decrease in the size of peroxisomes on day 5 of flooding and its increase on day 10 and more often formation of multivesicular structures (assembly of endomembranes) in the vacuole, which is considered as an autophagy enhancement of the cytoplasm under hypoxia, were noted. Differences in the ultrastructure of chloroplasts under the influence of soil flooding consisted in a significant, almost twofold increase in transient starch, the size and number of plastoglobules, especially on day 10, and swelling of granal and stroma thylakoids on day 10. Changes in the ultrastructure of desert madwort chloroplasts under the influence of soil flooding coincide with those of mesophytes studied in this respect. The obtained data on the chloroplast ultrastructure of desert madwort psammophyte prove the functioning of the photosynthetic apparatus in conditions of short-term soil flooding, which contributes to the survival of seedlings. The subsequent yellowing of leaves and death of plants indicates, as is assumed, the lack of systemic adaptation, primarily metabolic, that is, the transition to anaerobic metabolism, in this species to long-term hypoxia.