Differential Salt Tolerance and Similar Responses to Nitrogen Availability in Plants Grown from Dimorphic Seeds of Suaeda salsa

Seed heteromorphism is a phenomenon in which a single plant produces two or more types of seeds with different mor-phophysiological characteristics. Plants grown from different seed morphs also display differences in biomass, photosynthesis and plant fecundity. Seed heteromorphism is common in halophytes, which may experience temporal and spatial variation in the salinity of their growth environment. The ability to produce different types of seeds enables the halophyte to respond to saline environment by either varying salt tolerance or different dormancy status.

Several species of Suaeda can simultaneously produce brown and black seeds. Evidence showed that brown seeds are able to germinate at higher salinity and usually germinate faster than the black seeds. Many studies focused on the effects of environmental factors (salinity, temperature, etc.) to the dormancy and germination of heteromorphic seeds of halophytes. However, research of the differential growth of plants derived from heteromorphic seeds and their physiological mechanisms is less. 

Salinity and nitrogen are two important environmental factors that affect plant growth, photosynthetic pigment content, photosynthesis and chlorophyll fluorescence of halophytes. Suaeda salsa (L.) Pallas is an annual halophyte that produces two distinct types of seeds that differ in morphology, dormancy and germination. In order to investigate the growth responses of S. salsa to different levels of NaCl and nitrate nitrogen, and its significance from the viewpoint of photosynthetic physiology, Dr. JIANG Li et al. sowed S. salsa seeds belonging to the two morphs into a substrate with three salinity and three nutrient levels in a pot experiment in 2011.

The results showed that the shoot weight of plants from black seeds gradually decreased with the increase of salinity. Plants derived from both seed morphs had the same growth rates under similar nitrogen levels. Plant growth status was generally related to chlorophyll content and photosynthetic rates. Their study indicated that plants grown from the two different seed morphs of S. salsa exhibit different salt tolerance, but have similar responses to nitrate nitrogen. This is the first report on different responses to salinity and nitrogen availability in plants with heteromorphic seeds.

The result has been published on Flora, 2012. The paper can be downloaded from http://www.sciencedirect.com/science/article/pii/S0367253012000813.