The Bet-Hedging Strategies for Seedling Emergence of Calligonum mongolicum to Adapt to the Extreme Desert Environments in Northwestern China

Abstract

Calligonum mongolicum is a dominant native perennial shrub on sand dunes in arid deserts of northwestern China, and is therefore widely used in sand dune stabilization in these regions. However, it remains largely unknown how seedling emergence of C. mongolicum has adapted to unpredictable sand movement and extreme drought. Here we examined effects of seed burial depth, light intensity, and seed age on seedling emergence, and considered seed germination and seedling emergence strategies for the shrub’s adaption to the desert environment. In our pot experiment, the optimum seeding depth for emergence of C. mongolicum was 2 cm, indicating that for germination and seedling emergence only moderate sand burial is required. Light intensity at the surface soil (0 cm) was important for seedling emergence, while there was no significant difference between 50 and 20% light flux density, at burial depths of 1 and 2 cm, indicating that C. mongolicum seeds had adapted to sand burial, while not exposure from sand erosion. We also found C. mongolicum seedlings emerged in spring and in late summer to early autumn. Meanwhile, seedling emergence percentage for 3-year-old seeds was similar to that of 1-year-old seeds, which meant that C. mongolicum seeds were well preserved under normal sand dune conditions, thus were capable of developing a persistent, but shallow soil seed-bank. These results indicated that germination and seedling emergence take a bet-hedging strategies to adapt to variable desert environments. Our study confirmed that C. mongolicum desert shrubs combine strategies in its adaption to arid and variable sand environments.

The risk-takers and -avoiders: germination sensitivity to water stress in an arid zone with unpredictable rainfall

“…Bet-hedging refers to a seed’s ability to remain dormant or viable in the soil across seasons without committing to germination, and allows seeds to forego synchronous recruitment until conditions are suitable for plant establishment (Simons 2009; Gremer and Venable 2014). It is commonly observed in seeds from arid zones (Gremer et al 2016; Fan et al 2018; Lewandrowski et al 2018) because, under low rainfall and high temperatures, germination is a high-risk event. These bet-hedging traits were observed in H. leucoptera ; seeds have greater moisture requirements and lower germination proportions in hot conditions, and maintain high seed viability under physiological stress.…”

Organellar protein multi-functionality and phenotypic plasticity in plants

“…A bet hedging model assumes that organisms have the capacity to suffer reduced fitness under ideal conditions in exchange for increased fitness under stressful conditions [14]. In plants, the most common examples include variation in seed germination rates, so that a smaller population number in the first year affords an opportunity for staggered multi-year germination [15]. Flower timing can also display variation to accommodate reproduction under unfavourable conditions that might improve over time [16].…”

Lower dormancy with rapid germination is an important strategy for seeds in an arid zone with unpredictable rainfall

“…rhagodioides , a small proportion of seeds germinate upon maturity, or upon seed dispersal, but germination rate and proportion improve as seeds age. This suggests that seeds can remain in the soil or canopy for years and stagger germination across seasons, which spreads the risk of recruitment failure through time and increases the probably that favourable conditions for seedling establishment will occur during the lifespan of a seed cohort [30, 68]. Physiological dormancy in A .…”