Abstract
Anatomical and histochemical studies of ovary and caryopsis of sorghum reveal the importance of the chalazal complex in transporting nutrients from maternal sources to the filial diploid embryo and triploid endosperm. The presence of starch, protein, lipid, Ca, K, Mg, and Fe in various tissues at different stages of development can be revealed by a variety of histochemical techniques. Vascular supply ends at the base of the ovary and transport occurs through vascular parenchyma, pigment strand and nucellar projection where symplastic continuity is broken. Nutrients unloaded into an apoplastic placental sac then enter the endosperm and embryo through the aleurone transfer cells. The later possess characteristic wall ingrowth. The single layer of aleurone surrounding the endosperm may also help in transport during later stages of grain-filling. Grain-filling in C4 sorghum is compared with other C4 and C3 grasses showing the variety of strategies evolved to transport nutrients into filial tissues. Standardization of terminologies to describe the tissues of the crease region will help in further research and communication.
Highlights
The fruit of sorghum, as those of all cereals, is known as a caryopsis
Morphology and development of ovary The sorghum caryopsis develops from an ovary of a sessile and fertile spikelet associated with one or more pedicellate spikelets but without functional ovaries
During early stages of development, the ovary is still protected by glumes, lemma and palea at later stages the caryopsis is partially exposed from the sterile coverings
Summary
The fruit of sorghum, as those of all cereals, is known as a caryopsis. A mature caryopsis consists of a crushed pericarp and integuments derived from maternal tissues, and two filial structures: a diploid embryo and a triploid endosperm. As an extra-embryonic tissue and a product of an independent event of fertilization the endosperm has evolved to provide nourishment to its sibling embryo during germination (Becraft and Gutierrez-Marcos, 2012). Both the endosperm and the embryo store carbohydrates, proteins, lipids and minerals; their importance in human nutrition and growth of civilizations since the domestication of cereals, more than ten thousand years ago. The role of tissues associated with grain-filling in sorghum was investigated by Quinby (1972) and Received: 24 Apr 2020. Received in revised form: 10 Dec 2020.
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