Temperature characteristics in seed germination and growth of Zostera japonica Ascherson & Graebner from Ago Bay, Mie Prefecture, central Japan

Abstract

The optimal water temperature in seed germination and the upper critical water temperature in seedling growth were determined for Zostera japonica collected from Ago Bay, Japan. The relationship between the seed germination rates and seed storage period (0, 30, and 60 days) at 0°C was also examined. The optimal water temperature in seed germination was in the range 15-20°C regardless of the storage period, in which germination rates were up to 14%. Seedlings, grown from seeds up to 10 cm in total length, were cultured for 1 week at various water temperatures to measure their relative growth rates. The optimal water temperature in early growth was in the range 20-25°C; relative growth rates ranged from 3.8 to 4.2%. Seedlings could survive up to a water temperature of 29°C, but most seedlings withered at 30 or 35°C.The optimal water temperatures for seed germination and seedling growth were related to the seasonal changes of water temperature in the sampling site. Although seedlings were hardly observed in Ago Bay in summer, Z. japonica might extend its distribution as far as where the summer water temperature is lower than 29°C.

Effects of temperature, salinity and seed age on induction of Zostera japonica germination in North America, USA

“…In British Columbia, Z. japonica seedlings appear in March (Bigley, 1981;Harrison, 1982b). Freshly collected Z. japonica seeds from Japan exhibited low germination rates when placed in seawater at 10-23 • C without cold pre-treatment; subsequent exposure to fluctuating temperatures stimulated germination (Abe et al, 2009;Morita et al, 2011). However, a small proportion of the seeds may be non-dormant when shed and are capable of germinating in the absence of cold stratification, particularly under low salinity conditions (Morita et al, 2011).…”

“…Consequently, temperature and salinity cues may be important triggers for Z. japonica seed germination. Although Z. japonica seed germination in Japan is known to be strongly influenced by cold stratification (e.g., artificial cold exposure to mimic winter) and induction temperature (Abe et al, 2009;Morita et al, 2011), those experiments did not address salinity effects. Additionally, reviews highlighting factors known to influence seagrass seed germination call for further evaluation of the role of salinity in breaking dormancy (Orth et al, 2000(Orth et al, , 2006.…”

Coexistence between Zostera marina and Zostera japonica in seagrass beds of the Seto Inland Sea, Japan

“…Since there was no statistically significant difference by year, annual water temperature was not considered to be a factor for the decrease in shoot density, and annual water temperature was not a direct cause of the decrease in shoot density in both species after October 2011. Figure 8 shows the number of days in each year from 2010 to 2013 for which the daily mean water temperature was lower than 10°C; a temperature that may affect the germination of seagrass (Abe et al 2009;Kawasaki et al 1986). In 2011, the shoot density of Z. marina and Z. japonica was higher until June before the summer, and the number of days on which the daily mean water temperature was lower than 10°C was higher than in any other year at 43 days.…”

“…The upper part of seagrass is affected by water turbulence, and the lower part is affected by photosynthesis inhibition (Dennison and Alberte 1985;Duarte 1991;Mach et al 2010;Kendrick et al 2002). The habitats of Z. marina and Z. japonica are affected by salinity and depth (Greve and Krausen-Jensen 2005;Morita et al 2010;Abe et al 2009;Shafer et al 2011). For example, in the summer, Z. marina growth becomes difficult when the daily mean water temperature is 28°C or more.…”

Estimation of light requirement for growth of Zostera japonica cultured seedlings based on photosynthetic properties

“…Recently, it has been found that Z. japonica has expanded its distributional area to the North Pacific Coast of North America [3,4]. There have been some ecological reports on the Z. japonica populations in the subtropical and temperate areas of Asia [5][6][7][8][9] and along the Pacific Coast of North America [3,[10][11][12][13][14][15][16][17][18][19]. However, there have been few physiological reports until now [19][20][21].…”