Germination Response of Four Alien Congeneric Amaranthus Species to Environmental Factors

Abstract

Seed germination is the key step for successful establishment, growth and further expansion of population especially for alien plants with annual life cycle. Traits like better adaptability and germination response were thought to be associated with plant invasion. However, there are not enough empirical studies correlating adaptation to environmental factors with germination response of alien invasive plants. In this study, we conducted congeneric comparisons of germination response to different environmental factors such as light, pH, NaCl, osmotic and soil burials among four alien amaranths that differ in invasiveness and have sympatric distribution in Jiangsu Province, China. The data were used to create three-parameter sigmoid and exponential decay models, which were fitted to cumulative germination and emergence curves. The results showed higher maximum Germination (Gmax), shorter time for 50% germination (G50) and the rapid slope (Grate) for Amaranthus blitum (low-invasive) and A. retroflexus (high-invasive) compare to intermediately invasive A. spinosus and A. viridis in all experimental regimes. It indicated that germination potential does not necessarily constitute a trait that can efficiently distinguish highly invasive and low invasive congeners in four Amaranthus species. However, it was showed that the germination performances of four amaranth species were more or less correlated with their worldwide distribution area. Therefore, the germination performance can be used as a reference indicator, but not an absolute trait for invasiveness. Our results also confirmed that superior germination performance in wide environmental conditions supplementing high seed productivity in highly invasive A. retroflexus might be one of the reasons for its prolific growth and wide distribution. These findings lay the foundation to develop more efficient weed management practice like deep burial of seeds by turning over soil and use of tillage agriculture to control these invasive weed species.

Effect of Soil pH on the Growth, Reproductive Investment and Pollen Allergenicity of Ambrosia artemisiifolia L.

“…IAPs usually possess broader tolerance to environmental conditions, including pH (Dassonville et al, 2008 ; Hao et al, 2017 ), than crop and native plants, which have an optimum for pH mostly ranging from 5.5 to 6.5 (Islam et al, 1980 ; Köpp et al, 2011 ). This characteristic allows them to adapt to a great variety of soil types and thus to spread vigorously, also colonizing environments not suitable for native species (Sǎrǎteanu et al, 2010 ).…”

“…In this study, we aimed to investigate how pH affects germination, growth-related traits, reproductive investment, pollen production and allergenicity of A. artemisiifolia . We grew plants in controlled conditions in a replicated experimental design and used prediction models to accurately estimate the species performance in relation to pH values (Mohebbi and Mahler, 1989 ; Robson, 1989 ; Kidd and Proctor, 2001 ; Hao et al, 2017 ). In particular, we used nonlinear models following a sigmoid pattern (i.e., logistic curves) to determine how soil pH affects the germination, growth rate of vegetative traits and reproductive investment of A. artemisiifolia (Yin et al, 2003 ; Sun and Frelich, 2011 ; Paine et al, 2012 ; Chen et al, 2014 ) and if soil pH has an effect on the pollen allergenicity of the species.…”

Persistence and Changes in Morphological Traits of Herbaceous Seeds Due to Burial in Soil

“…The morphological changes and changes in seed mass over time spent in soil can also be well described by logistic regression in many species, and it seems plausible that this approach will find wide application in seed ecology studies. In addition to seed persistence [17,42,49] and morphology (this study), logistic models were recently applied for describing germination response to environmental conditions [50]. Thus, we propose using these models in situations in which the response of this type of seed to a focal variable can be expected.…”

Environmental factors effecting the germination and seedling emergence of two populations of an aggressive agricultural weed; Nassella trichotoma

“…The size of a seed may determine the depth from which it emerges; large seeds may have greater energy reserves, allowing emergence from greater depths than smaller seeds. The effect of seed size on emergence was observed in four species of Amaranthus, with the lightest species ( Amaranthus spinosus) having significantly shallower optimal burial depth compared to the denser species ( Amaranthus viridis) [ 28 ]. Germination of photoblastic seeds decrease with an increase in burial depth.…”

“…However, it generally does not affect their viability when these seeds were alleviated from the salinity stress, and normal germination was observed. It is common for weeds to tolerate a wide range of soil pH levels [ 4 , 28 , 33 , 34 ] which is a key trait of an invasive generalist species. However, by identifying if particular soil factors, such as pH and salinity enhance germination, regions at risk will be easier to identify.…”