Daytime Dynamics of the Photosynthetic Apparatus’ Structural and Functional Parameters in Wild Halophytes

Dynamics of the photosynthetic apparatus' (PA) structural and functional parameters during the day was investigated in euhalophyte Salicorniaperennans Willd., crynohalophyte Limoniumgmelinii (Willd.) O. Kuntze, and glycohalophyte Artemisiasantonica L. The greatest PA activity judging from the rate of СО₂ consumption/release by the leaves was observed in the morning. In salt-accumulating (S. perennans) and salt-eliminating (A. santonica) species, the rate of photosynthesis was greater than in L. gmelinii plants possessing the systems of salt excretion. In A. santonica and S. perennans, the content of green pigments decreased during the day, while it remained permanent in L. gmelinii. During the day, the ratio between plastid lipids and pigments increased in A. santonica and S. perennans. In chloroplast lipids from S. perennans, a decrease in the relative content of monogalactosyldiacylglycerol (MGDG) was compensated for by a rise in relative content of digalactosyldiacylglycerol (DGDG), with the contribution of sulfoquinovosyldiacylglycerol (SQDG) and phosphatidylglycerol (PG) remaining the same. In the chloroplasts from L. gmelinii, the proportion of neutral lipids MGDG and DGDG did not change in contrast to the level of anionic lipids SQDG and PG. In A. santonica, we detected changes in both neutral and anionic lipids. A high proportion of unsaturated FA (UFA) (over 70%) in the total pool of FA was mainly accounted for by α-linolenic acid. It was found that the proportion of saturated FA tended to increase in the evening. All the revealed structural and functional reorganizations of PA associated with fluctuation of pigment-lipid resources of thylakoid membranes were adaptive and aimed at optimization of photosynthesis under specific environmental conditions.