Effect of Seed Position on Parental Plant on Proportion of Seeds Produced with Nondeep and Intermediate Physiological Dormancy.

Carol C. Baskin,Dun Y. Tan,Juan J. Lu,Jerry M. Baskin

doi:10.3389/fpls.2017.00147

Carol C. Baskin, Dun Y. Tan + Show 2 more

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https://doi.org/10.3389/fpls.2017.00147

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Abstract

The position in which seeds develop on the parental plant can have an effect on dormancy-break and germination. We tested the hypothesis that the proportion of seeds with intermediate physiological dormancy (PD) produced in the proximal position on a raceme of Isatis violascens plants is higher than that produced in the distal position, and further that this difference is related to temperature during seed development. Plants were watered at 3-day intervals, and silicles and seeds from the proximal (early) and distal (late) positions of racemes on the same plants were collected separately and tested for germination. After 0 and 6 months dry storage at room temperature (afterripening), silicles and seeds were cold stratified for 0–16 weeks and tested for germination. Mean daily maximum and minimum temperatures during development/maturation of the two groups of seeds did not differ. A higher proportion of seeds with the intermediate level than with the nondeep level of PD was produced by silicles in the proximal position than by those in the distal position, while the proportion of seeds with nondeep PD was higher in the distal than in the proximal position of the raceme. The differences were not due only to seed mass. Since temperature and soil moisture conditions were the same during development of the seeds in the raceme, differences in proportion of seeds with intermediate and nondeep PD are attributed to position on parental plant. The ecological consequence of this phenomenon is that it ensures diversity in dormancy-breaking and germination characteristics within a seed cohort, a probable bet-hedging strategy. This is the first demonstration of position effects on level of PD in the offspring.

Highlights

According to the Nikolaeva-Baskin classification system, there are five classes of seed dormancy, i.e., physiological dormancy (PD), morphological dormancy (MD), morphophysiological dormancy (MPD), physical dormancy (PY), and combinational dormancy (PY + PD) (Baskin and Baskin, 2014)
Nondeep PD can be broken by high (≥15◦C) or low (0–10◦C and wet, i.e., cold stratification) temperatures, depending on the species, and it is the most common kind of seed dormancy on Earth
Exposure of seeds with intermediate PD to high temperatures for 2–3 months before the beginning of cold stratification significantly decreases the length of the cold treatment required to break dormancy (Baskin and Baskin, 2014)

Summary

Introduction

According to the Nikolaeva-Baskin classification system, there are five classes of seed dormancy, i.e., physiological dormancy (PD), morphological dormancy (MD), morphophysiological dormancy (MPD), physical dormancy (PY), and combinational dormancy (PY + PD) (Baskin and Baskin, 2014). Nondeep PD can be broken by high (≥15◦C) or low (0–10◦C and wet, i.e., cold stratification) temperatures, depending on the species, and it is the most common kind of seed dormancy on Earth. Exposure of seeds with intermediate PD to high temperatures for 2–3 months before the beginning of cold stratification significantly decreases the length of the cold treatment required to break dormancy (Baskin and Baskin, 2014). Seeds of some species, including those of Thlaspi arvense (Brassicaceae) (Hume, 1994), collected in the early part of the growing season when temperatures are relatively low, are more dormant than those collected late in the growing season when temperature are relatively high Germination percentage of early- and latecollected seeds of Brassica campestris was the same (Singh et al, 1976)

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