Preface

Abiotic stresses such as salinity, drought, and temperature greatly affect seed physiology, plant growth, and plant development. Drought and heat stress represent some of the main abiotic constraints faced by plants. Any increase in the incidence and strength of these stressors, either individually or in combination, significantly decreases crop productivity, thus putting future global food security at risk.

One of the most critical stressors is temperature since it can cause huge economic and agricultural losses. The temperature has a great influence on seed physiological processes such as seed filling, embryo development, reserve compound synthesis and storage in the endosperm, and so on during the vegetative and reproductive stages.

Drought and heat stress significantly affect seed yields by reducing seed size, number, and quality. High temperatures can reduce the period of grain development, causing huge repercussions in grain filling and yield reduction in many crop plants. For example, the increase of 1 °C in average temperature can result in a 10% reduction in crop yield for species such as rice. Increased temperature also reduces crop quality. The extent of impairment during the reproductive phase of crop growth, largely affecting the seed-filling process, is a key cause of significant yield losses. Seed filling is influenced by some metabolic pathways, particularly the production and translocation of photoassimilates from leaves to seeds, such as importing precursors of reserves biosynthesis. The metabolic control of these processes is very sensitive to water deficiency and high temperatures due to enzymes and protein transports involved in metabolism and located in leaves and seeds. Moreover, the combination of stressors is tremendously unfavorable for seed yield and quality. This book highlights potential markers of target sites for regulating seed-filling events and how they are affected by abiotic stresses.

It also discusses primary dormancy, which is strongly influenced by environmental factors during seed development. Seed dormancy is controlled by several environmental factors such as temperature, light, and duration of seed storage. Understanding how these factors affect seed dormancy and germination during seed maturation is necessary for crop production. For example, an appropriate level of seed dormancy is needed to produce cereal crops. Humidity and low temperature throughout seed maturation are associated with a lack of seed dormancy in various cereal cultivars. The oilseed is affected by high temperatures during seed filling, which reduces seed dormancy. High temperature during early endosperm development leads to seed germination and seedling growth in rice.

This book presents comprehensive information on the genetic mechanisms and biochemical and physiological cues that govern seed filling, seed development features under stress environments, seed dormancy and germination, and agronomic management to help crops develop resilience to climate change.

> **Jose C. Jimenez-Lopez** Estacion Experimental del Zaidin, Spanish National Research Council (CSIC), Granada, Spain

**Chapter 1**

**Abstract**

Seed Filling

*and Murat Mutlucan*

hormones, storage reserves

**1. Introduction**

*Sercan Önder, Sabri Erbaş, Damla Önder, Muhammet Tonguç* 

The synthesis of seed storage reserves occurs during seed filling, and many seeds contain large and characteristic levels of polymeric reserves. Storage reserves are found in the endosperm of cereal seeds and in the endosperm and/or cotyledons of dicot seeds depending of the plant crop species. Recently progress has been made in understanding the complex network of genetic regulation associated with seed filling. These advances in storage reserve quantity and nutrient quality contribute to a comprehensive understanding of reserve composition, synthesis, and regulation. Phytohormones such as abscisic acid (ABA), cytokinin, gibberellic acid, Indole-3-acetic acid (IAA), ethylene and their interactions play critical roles in seed filling and development. At different stages of seed development, the levels of different hormones such as ABA, IAA zeatin and zeatin riboside changes gradually from the beginning of the process to maturity. In addition, the quality and yield of seed storage reserves are significantly affected by the environmental conditions before and during the synthesis of the reserves. Given the fateful importance of seed storage reserves for food and feed and their use as sustainable industrial feedstock to replace dwindling fossil reserves, understanding the metabolic and developmental control of seed filling will be an important focus of plant research.

**Keywords:** early maturation, environmental factors, genetic regulation, plant

Seed development is divided into three stages: embryogenesis, which includes embryo development, early maturation, or seed filling, which includes the accumulation of storage reserves; and late maturation, which includes seed desiccation and the transition to dormancy. After seed filling and desiccation, seed longevity increases up to 30-fold and places the embryo in a dormant state. The seed filling period accounts for between 10 and 78% of the total seed development period, but its importance during seed filling is still overlooked. Seed filling is a crucial stage for all seed plants, involving the synthesis of carbohydrates, lipids, and proteins, as well as the mobilization and accumulation of various components in the developing seeds. Although the metabolic pathways responsible for the synthesis of storage molecules are well known, their regulation is not well understood. Although seed filling is under genetic control, these developmental processes are influenced by the environmental factors, such as heat and drought stress. Therefore, environmental factors have major impacts on the qualitative and quantitative characteristics of seed development and
