Abstract
There is large variation in seed mass within P. oreoselinum (L.) Moench selected for the present study from two contrasting habitats: roadside and oak forest. Effect of seed position within a plant and of soil nutrients on seed mass, germination and seedlings growth were studied. Within an individual plant, seed mass decreased with umbel order and seeds from the central umbellet of the umbel were lighter than those from the outer edge, suggesting that variation in seed mass within an individual plant was due to the position effect. There was a significant relationship between seed mass and total germination. Covariate analysis showed the differences between sites in seed macronutrient contents were caused by respective differences in seed mass and soil macronutrients. This indicates substantial variation in the amount of reserves initially available for seedling growth. In conclusion, phenotypically-based variation in seed mass may arise from soil conditions, maternal traits or combination of the two. High variability in seed mass of P. oreoselinum favours its widespread geographic distribution. These results suggest that with respect to germination characteristics large seeds from primary order have a competitive advantage over small seeds produced on secondary umbels because they have higher overall germination.
Highlights
Seed size can affect germination time, germination percentage, dispersal, seed water relation, as well as seedling establishment, growth, survival, and it has important ecological consequences[1,2,3,4,5]
Seeds produced by the primary umbels were significantly (p-value = 0.0217) heavier (5.8 ± 0.3 mg) than those from the secondary ones (4.8 ± 0.4 mg) (Fig. 1a)
Both shoot biomass and root biomass of the seedling from the seeds on the primary umbel were significantly higher than those of the seedlings from seeds on the secondary umbels (Table 6). These results suggests that the seedlings from seeds on the primary umbels were significantly more vigorous than those from seeds on the secondary umbels
Summary
Seed size (mass) can affect germination time, germination percentage, dispersal, seed water relation, as well as seedling establishment, growth, survival, and it has important ecological consequences[1,2,3,4,5]. An increase in the macronutrient concentration in surrounding environment has often led to the production of seeds that are heavier and have greater quantities and concentrations of N (nitrogen) and P (phosphorus)[9] This plastic response can have important fitness consequences for developing seedlings. Effects of seed position within a plant and of soil nutrients on seed mass, germination and seedlings growth were studied. The objectives of this study were the following (1) to analyze the effect of the umbel order and umbellet position on seed mass and seed germination; (2) to quantify the degree of seed mass variation in P. oreoselinum among populations and plants within populations, and within individuals plants; (3) to determine possible relation between seed macronutrient content and respective soil macronutrients content; and (4) to examine the relationship between seed mass and seed macronutrient content
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