J Plant Ecol ›› 2020, Vol. 13 ›› Issue (3): 256-265.doi: 10.1093/jpe/rtaa008

• Research Articles •     Next Articles

Dynamics in the emergence of dormant and non-dormant herbaceous species from the soil seed bank from a Brazilian dry forest

José Djalma de Souza1, *, Bruno Ayron de Souza Aguiar1, Danielle Melo dos Santos2, Vanessa Kelly Rodrigues de Araujo1, Júlia Arruda Simões1, Juliana Ramos de Andrade1 and Elcida de Lima Araújo1   

  1. 1 Departamento de Biologia, Universidade Federal Rural de Pernambuco, Recife, Pernambuco, Brazil, 2 Universidade Federal de Pernambuco – Centro Acadêmico de Vitória, Pernambuco, Brazil

    *Corresponding author. E-mail: jdds.djalma@hotmail.com
  • Received:2019-11-10 Revised:2020-02-11 Accepted:2020-02-28 Online:2020-03-04 Published:2020-06-01

Abstract:

Aims

In dry tropical forests, herbaceous species may have dormancy mechanisms and form persistent and transient seed banks in the soil. Evolutionarily acquired, these mechanisms are efficient for the establishment and survival of these herbs, especially in forests with unpredictable climates, such as the Caatinga. Thus, our objective was to verify whether the studied herbaceous species adopt the physical dormancy mechanism and how these natural barriers are overcome, to understand the temporal dynamics existing in the soil seed bank from a Brazilian dry tropical forest.

Methods

Seeds of five native herbaceous species from the Caatinga forests were selected and submitted to pre-germinative treatments for verifying the presence of physical dormancy. We collected soil samples in the rainy and dry seasons for four consecutive years and monitored the emergence of the selected herbaceous in the greenhouse. We verified the differences in germination and seed bank emergence in the soil by generalized linear models.

Important Findings

The presence and absence of physical dormancy were observed in seeds from Caatinga herbaceous species. We found intraspecific and interspecific differences in the herbaceous emergence from soil seed banks between years and climatic seasons. In perennial herbs, consecutive lack of emergence between seasons and years was frequent, which suggests a direct relationship with the mechanism of physical dormancy and the environmental conditions necessary to overcome integument barriers. In these species, seed dimorphism and dormancy may confer additional advantages to their survival. Moreover, presenting intermediate levels of physical dormancy in an annual species may be an evolutionary adjustment to rainfall unpredictability. In contrast, we found that the annual herb without dormancy is more sensitive to seasonal and interannual climate changes, as evidenced by the increase and significant reduction of its emergence in the soil seed bank. These differences acquired evolutionarily are advantageous for the establishment of herbaceous populations, mainly in semiarid regions with an unpredictable climate.

Key words: establishment, herbaceous species, physical dormancy, seed bank, seed germination, semiarid

摘要:

在干旱的热带森林中,草本植物可能具有休眠机制,并在土壤中形成持续和短暂的种子库。这一由进化而获得的机制对草本植物的建植和生存,特别是在气候不可预测的森林生态系统中,具有重要生态适应意义。因此,本研究的目的是验证草本植物是否具备物理休眠机制,以及这些植物是如何克服这些自然屏障的,并最终理解巴西干旱热带森林土壤种子库中种子萌发时间动态。本研究选择巴西 Caatinga 森林中的5种本地草本植物的种子,经过发芽前处理来验证是否存在物理休眠。连续4年在雨季和旱季收集土壤样品,并监测这些草本植物种子在温室中的萌发动态。利用广义线性模型验证种子萌发和出苗率的差异。研究结果表明Caatinga森林中的草本植物种子存在着物理休眠和非物理休眠;而且草本植物从土壤种子库中出苗的种内和种间存在着年份和季节的差异。对于多年生草本植物,不同季节和年份频繁出现不出苗的现象,这可能与物理休眠机制和克服种皮障碍所需的环境条件有关。在这些物种中,种子的二态性和休眠可能给它们的生存带来额外的优势。此外,在一年生植物中出现中等水平的物理休眠可能是对降雨不可预测性的进化调整。相比之下,我们发现没有休眠的一年生草本植物对季节和年际气候变化更敏感,这可以从土壤种子库中其出苗率的增加和显著减少得到证明。这些通过进化获得的种子休眠差异有利于那些分布在气候变化无常的半干旱地区草本植物种群的建立。

关键词: 草本植物, 半干旱, 种子萌发, 植株建立, 物理休眠

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