Abstract
It is generally accepted that seedlings from large seeds are more tolerant to defoliation than those from small seeds due to the additional metabolic reserves present in the large seeds. However, information on the effects of amount of seed reserves (cotyledon removal) from seedlings resulting from large vs. small seeds on seedling growth and long‐term survival in the field is limited. Five legume species with different sizes of seeds were sown in the field and none, one, or both cotyledons removed 7 days after seedling emergence. Seedling biomass, relative growth rate (RGR) and survival were determined at different time. Cotyledon removal, species, and their interaction had significant effects on seedling growth and survival. During the period between 33 and 70 days, seedlings from large seeds had a significantly lower RGR than those from small seeds. Biomass, RGR, and survival of seedlings from large seeds were significantly reduced by removal one or both cotyledons, whereas those of seedlings from small seeds were not affected. Seed energy reserves are more important for the early growth of seedlings from large seeds than for those from small seeds. The overall effect of cotyledon removal on growth and survival varies with seed size (i.e., energy reserves) with seedlings from small seeds being less sensitive than those from large seeds under field conditions.
Highlights
Seed size varies from 0.0001 mg for the orchids to 20 kg for the double coconut (Harper & Moore, 1970; Moles et al, 2005), and these variations in mass have been assumed to have substantial effects on seed germination, seedling recruitment, and plant fitness (Armstrong & Westoby, 1993; Hanley & May, 2006; Leishman, Wright, Moles, Westoby, & Fenner, 2000)
We hypothesized that: (1) seedlings from large seeds are more dependent on seed reserves than those from small seeds, and growth of seedlings from small seeds is less affected by cotyledon removal than that of seedlings from large seeds; (2) seedlings from small seeds have a higher relative growth rate than those from large seeds; the initial advantage of seedling size from large seeds will decrease with seedling growth; (3) survival percentage of seedlings from large seeds is higher than that from small seeds at an early time but not in the long term
Our data clearly show that seedlings from species with small seeds were less affected by cotyledon removal than those from species with large seeds, regardless of seedling growth or their survival probability in the field
Summary
Seed size varies from 0.0001 mg for the orchids to 20 kg for the double coconut (Harper & Moore, 1970; Moles et al, 2005), and these variations in mass have been assumed to have substantial effects on seed germination, seedling recruitment, and plant fitness (Armstrong & Westoby, 1993; Hanley & May, 2006; Leishman, Wright, Moles, Westoby, & Fenner, 2000). Recent studies (Giertych & Suszka, 2011; Yi et al, 2012, 2013, 2015) on oaks (Quercus) showed that seed germination and seedling survival were little affected by cotyledon removal, suggesting that cotyledonary reserves in acorns may be not crucial for supporting seedling development and may serve as food for manipulating seed predators and dispersers These controversial results of seed size effects on seedling tolerance to cotyledon removal may be related to cotyledon type (Baraloto et al, 2005), seedling growth stage (Hanley & May, 2006; Seiwa & Kikuzawa, 1991, 1996), cotyledon removal time (Hanley & Fegan, 2007), and seedling growing conditions (Lamont & Groom, 2002). We hypothesized that: (1) seedlings from large seeds are more dependent on seed reserves than those from small seeds, and growth of seedlings from small seeds is less affected by cotyledon removal than that of seedlings from large seeds; (2) seedlings from small seeds have a higher relative growth rate than those from large seeds; the initial advantage of seedling size from large seeds will decrease with seedling growth; (3) survival percentage of seedlings from large seeds is higher than that from small seeds at an early time but not in the long term
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