Microgravity effects on different stages of higher plant life cycle and completion of the seed‐to‐seed cycle

Abstract

Human inhabitation of Space requires the efficient realisation of crop cultivation in bioregenerative life-support systems (BLSS). It is well known that plants can grow under Space conditions; however, perturbations of many biological phenomena have been highlighted due to the effect of altered gravity and its possible interactions with other factors. The mechanisms priming plant responses to Space factors, as well as the consequences of such alterations on crop productivity, have not been completely elucidated. These perturbations can occur at different stages of plant life and are potentially responsible for failure of the completion of the seed-to-seed cycle. After brief consideration of the main constraints found in the most recent experiments aiming to produce seeds in Space, we focus on two developmental phases in which the plant life cycle can be interrupted more easily than in others also on Earth. The first regards seedling development and establishment; we discuss reasons for slow development at the seedling stage that often occurs under microgravity conditions and can reduce successful establishment. The second stage comprises gametogenesis and pollination; we focus on male gamete formation, also identifying potential constraints to subsequent fertilisation. We finally highlight how similar alterations at cytological level can not only be common to different processes occurring at different life stages, but can be primed by different stress factors; such alterations can be interpreted within the model of 'stress-induced morphogenic response' (SIMR). We conclude by suggesting that a systematic analysis of all growth and reproductive phases during the plant life cycle is needed to optimise resource use in plant-based BLSS.

Leaf Anatomy and Photochemical Behaviour ofSolanum lycopersicumL. Plants from Seeds Irradiated with Low-LET Ionising Radiation

“…Any variations in growth parameters in Space-oriented ecologically closed systems can determine valuable changes in terms of optimisation of volume and resource recycling. These changes can be straightaway converted into economic saving or waste [9]. For example, the increase in the number and size of leaves induced in “Microtom” especially by low doses of irradiation can be beneficial to atmosphere regeneration of pressurised modules, provided that formed leaves do not show structural aberrations which reduce their function.…”

“…Focusing on Space exploration, there is common agreement that long-term human permanence in Space relies on the possibility to regenerate resources in Bioregenerative Life Support Systems (BLSSs) where plants can play a key role [6, 7]. Plant growth is not prevented in Space; however, although plants can be more resistant than other organisms to specific Space factors (including reduced gravity and cosmic radiation), there is also evidence of altered growth and reduced fitness [2, 8, 9]. Many studies have indicated the occurrence of either positive or negative phenomena in plants exposed to low-LET (linear energy transfer) (e.g., X- and gamma-rays) and high-LET (e.g., protons and heavy ions) ionising radiation [2].…”

Plant biology in space: recent accomplishments and recommendations for future research

“…New information and insights have been obtained with regard to both vegetative and reproductive growth (for review see e.g. Correll & Kiss 2008;Ferl et al 2002; see also De Micco et al 2014a;Ueda et al 2014). Major progress is coming from investigations of plant hormone signalling pathways, in particular those involved in IAA transport (Geisler et al 2014;Ueda et al 2014).…”

Plant biology in space

“…Although we are aware that seed‐to‐seed cycles can be achieved, the review from De Micco et al . () highlights some negative effects of space conditions on plant growth and the consequences for crop productivity. Generally supporting this view, Paradiso et al .…”