@entity4663 are small, ubiquitous, nitrogenous compounds that scavenge reactive @entity26 species and stabilize the structure and function of the photosynthetic apparatus in response to abiotic stresses. Molecular details underlying @entity4664 -mediated photoprotective mechanisms are not completely resolved. This study investigated the role of @entity11667 ( @entity18162 ) in the structure and function of the photosynthetic apparatus. @entity523 seedlings were subjected to salinity-alkalinity stress with and without foliar application of Spd, and photosynthetic and morphological parameters were analyzed. Leaf dry weight and net photosynthetic rate were reduced by salinity-alkalinity stress. Salinity-alkalinity stress reduced photochemical quenching parameters, including maximum photochemistry efficiency of photosystem II, quantum yield of linear electron flux, and coefficient of photochemical quenching (qP). Salinity-alkalinity stress elevated nonphotochemical quenching parameters, including the de-epoxidation state of the xanthophyll cycle and nonphotochemical quenching (NPQ). Microscopic analysis revealed that salinity-alkalinity stress disrupted the internal lamellar system of granal and stromal thylakoids. Exogenous Spd alleviated the stress-induced reduction of leaf dry weight, net photosynthetic rate, and qP parameters. The NPQ parameters increased by salinity-alkalinity stress were also alleviated by Spd. Seedlings treated with exogenous Spd had higher @entity7695 (Z) contents than those without Spd under salinity-alkalinity stress. The chloroplast ultrastructure had a more ordered arrangement in seedlings treated with exogenous Spd than in those without Spd under salinity-alkalinity stress. These results indicate that exogenous Spd can alleviate the growth inhibition and thylakoid membrane photodamage caused by salinity-alkalinity stress. The Spd-induced accumulation of Z also may have an important role in stabilizing the photosynthetic apparatus.

The Photoprotective Role of @entity11667 in XXXX Seedlings under Salinity-Alkalinity Stress.

@entity26 :: ('MESH:D010100', 'Chemical') :: ['oxygen'] @entity7695 :: ('MESH:C005881', 'Chemical') :: ['zeaxanthin'] @entity4663 :: ('MESH:D011073', 'Chemical') :: ['Polyamines'] @entity523 :: ('4081', 'Species') :: ['Tomato'] @entity4664 :: ('CHEBI:60143', 'Chemical') :: ['polyamine'] @entity18162 :: ('CHEBI:35785', 'Chemical') :: ['Spd'] @entity11667 :: ('MESH:D013095', 'Chemical') :: ['spermidine']
@entity523 :: (4081,Species) :: ['Tomato']
