**Seed Priming: New Comprehensive Approaches for an Old Empirical Technique**

Stanley Lutts, Paolo Benincasa, Lukasz Wojtyla, Szymon Kubala S, Roberta Pace, Katzarina Lechowska, Muriel Quinet and Malgorzata Garnczarska

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/64420

#### **Abstract**

Advanced molecular tools applied to translational research programs in seed science are ex‐ pected to address key societal challenges in agriculture and industry while ensuring envi‐ ronmental protection. Kanai et al. extensively described how the available fundamental knowledge on lipid biosynthesis could be used for increasing oil production in crops. Gó‐ mez-Maqueo et al. highlighted the potentialities of modulating cell wall properties to en‐ hance seed germination traits. On the other side, Ruiz-Téllez et al.reviewed the potentialities of seed technology for helophyte production to be used in green wetlands with horizontal

We hope that this book, which combines different aspects of basic and translational research in seed biology, will attract the attention of researchers and technologists from academia and industry, providing points for interactive and fruitful discussion on this fascinating topic.

This work was supported by grants from the University of Pavia. During this book edition, SSA has been awarded by a research contract funded by CARIPLO Foundation (Action 3, Code 2013-1727)—Integrated Project "Advanced Priming Technologies for the Lombardy Agro-Seed Industry (PRIMTECH)." The financial support from Fundação para a Ciência e a Tecnologia (Lisbon, Portugal) is acknowledged through research unit "GREEN-it: Bioresour‐ ces for Sustainability" (UID/Multi/04551/2013) and presents SSA postdoctoral grant

[1] Araújo SS, Paparella S, Dondi D, Bentivoglio A, Carbonera D, Balestrazzi A. Physical methods for seed invigoration: advantages and challenges in seed technology. Frontiers in

[2] Paparella S, Araújo SS, Rossi G, Wijayasinghe M, Carbonera D, Balestrazzi A. Seed pri‐ ming: state of the art and new perspectives. Plant Cell Reports 2015 34: 1281–1293. DOI:

[3] Ragonnaud M. The EU seed and plant reproductive material market in perspective: a focus on companies and market shares (2013). Policy Department B: Structural and Cohe‐ sion Policies. European Parliament Committee on Agriculture and Rural Development.

**Dr. Susana Araújo**

Oeiras, Portugal

**Alma Balestrazzi**

Pavia, Italy

Plant Cell Biotechnology Laboratory

Universitá degli Study di Pavia,

surface for wastewater treatment.

**Acknowledgments**

VIII Preface

(SFRH/BPD/108032/2015).

10.1007/s00299-015-1784-y

Brussels: European Commission

Plant Science 2016 7: 646. DOI: 10.3389/fpls.2016.00646

**References**

Seed priming is a pre-sowing treatment which leads to a physiological state that enables seed to germinate more efficiently. The majority of seed treatments are based on seed imbibition allowing the seeds to go through the first reversible stage of germination but do not allow radical protrusion through the seed coat. Seeds keeping their desiccation tolerance are then dehydrated and can be stored until final sowing. During subse‐ quent germination, primed seeds exhibit a faster and more synchronized germination and young seedlings are often more vigorous and resistant to abiotic stresses than seedlings obtained from unprimed seeds. Priming often involves soaking seed in predetermined amounts of water or limitation of the imbibition time. The imbibition rate could be somehow controlled by osmotic agents such as PEG and referred as osmopriming. Halopriming implies the use of specific salts while "hormopriming" relies on the use of plant growth regulators. Some physical treatments (UV, cold or heat,..) also provide germination improvement thus suggesting that priming effects are not necessarily related to seed imbibition. A better understanding of the metabolic events taking place during the priming treatment and the subsequent germination should help to use this simple and cheap technology in a more efficient way.

**Keywords:** germination, omics approaches, priming, seedling growth, stress resist‐ ance

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

### **1. Introduction**

Efficient seed germination is important for agriculture. Successful establishment of early seedling indeed requires a rapid and uniform emergence and root growth. Germination of orthodox seeds commonly implies three distinct phases (**Figure 1**) consisting in (1) Phase I: seed hydration process related to passive imbibition of dry tissues associated with water movement first occurring in the apoplastic spaces; (2) Phase II: activation phase associated with the re-establishment of metabolic activities and repairing processes at the cell level; and (3) Phase III: initiation of growing processes associated to cell elongation and leading to radicle protrusion. Phases I and III both involve an increase in the water content while hydration remains stable during Phase II. It is commonly considered that before the end of Phase II, germination remains a reversible process: the seeds may be dried again and remain alive during storage and able to subsequently re-initiate germination under favorable conditions.

**Figure 1.** Seed hydration curves and germinating phases in unprimed and primed seeds.

Water-based seed priming is defined as a pre-sowing treatment that partially hydrates seeds without allowing emergence [1]. Various treatments may indeed be applied during the reversible phase of germination (point 3). They widely differ according to the osmotic potential of the priming solution, the duration, the external temperature, and the presence of specific chemical compounds. The efficient treatments trigger metabolic processes activated during the phase II of germination, which are then temporally stopped before a loss of desiccation occurs (**Figure 1**) [2].

The overall consequence of seed priming consists in an increased seed vigor defined as the whole set of properties conditioning seed lots performance in a wide range of environment [3]. Priming strategies may afford several economic and agronomic advantages to cultivated plants (point 4). Numerous data published in the literature indeed reported an improvement in the rate and uniformity of germination but also an obvious improvement in the behavior of the obtained seedlings in terms of plant growth and stress resistance.

Although priming is used since decades by farmers and seed companies to improve germi‐ nation, it can also occur under natural plant conditions. This is more especially the case in serotinous plants growing in deserts and able to retain their seeds for a long time. These seeds indeed undergo several hydration-dehydration cycles enhancing subsequent germination after final seed dispersion caused by heavy rain [4]. From a general point of view, the priming process not only concerns seeds but also the whole plant system itself and may be defined as an induced state whereby a plant reacts more rapidly and more efficiently to a stress [5]. In this acception, plants exposed to a primary constraint are triggering a set of temporary metabolic adaptation leading to a stress memory and allowing them to adapt more efficiently to subsequent episodes of stress [6, 7].

Although the interest of seed priming has been demonstrated since a long time, the underlying physiological and biochemical basis of this fascinating process remain poorly understood. Holistic approaches related to omics tools now provide new opportunities to elucidate the molecular components of the priming phenomena. Similarly, nondestructive and noninvasive methods such as digital image technology may be used in a more precise way to study the kinetics of imbibition in relation to the modification of the seed ultrastructure. This chapter reviews the most recent progresses accomplished in the understanding of the seed priminginduced modifications.
