Hormonal and genetic control of leaf and vein development in maize

[EMBARGOED UNTIL 8/1/2023] Grasses (Poaceae) have successfully colonized diverse terrestrial ecosystems and impacted human civilization by producing the bulk of world food supply. The grass leaf is distinct for having a sheathing base and strap-like blade -- an evolutionary modification from the petioled leaf of eudicots. A further innovation in the grass leaf is the venation pattern composed of parallel longitudinal veins (long veins) interlinked by transverse veins. The long veins are formed as the leaf grows wide early in the development. The small indolic plant hormone, auxin, controls leaf and vein development in plants. However, how it controls leaf and vein development in grasses is not wellunderstood. In Chapter 1, I review the literature on leaf vein development and highlight the knowledge gap on the role of auxin in the regulation of vein formation in grasses. In Chapters 2 and 3, I address two important aspects of grass leaf and vein research using Zea mays as the model system: 1) to develop a tool that will enable high-throughput analysis of vein number and morphology; and 2) to investigate the roles of auxin and two other plant growth hormones, gibberellic acid (GA) and cytokinin (CK), in regulating the leaf width and long vein number in grasses. Through collaboration, I helped develop the first image analysis framework dedicated for the parallel venation in grasses which can quantify vein traits and detect vein patterning defects. In Chapter 2, I describe the first detailed spatial-temporal map of auxin, CK, and GA during early leaf development in a grass species. I propose a conceptual model for hormonal regulation of medial-lateral growth and vein proliferation. This model can be used to develop testable predictions about hormonal regulation of leaf phenotypes altered by mutation or environmental response in maize and other grass species. Finally, in Chapter 4, I offer future perspectives about decoupling leaf growth and vein formation by focusing on spatialtemporal auxin response, which will be important for the targeted improvement of vein density to increase productivity in grass crops. Therefore, this thesis contributes technical innovations, advances the understanding of plant development, and provides new insights for future work.Includes bibliographical references

Comparative morpho-anatomy of Medinilla magnifica Lindl. and Medinilla sp. (Melastomataceae)

Medinilla Gaud. (Melastomataceae) is a genus of tropical plants that has been extensively studied in terms of taxonomy and systematics. However, information about its functional morpho-anatomy is very limited. This study aimed to compare the morpho-anato

Growth and immune response of giant freshwater prawn Macrobrachium rosenbergii (De Man) postlarvae fed diets containing Chlorella vulgaris (Beijerinck)

A 50‐day growth trial was conducted to evaluate the efficacy of Chlorella vulgaris (Beijerinck) as an ingredient in the diets of giant freshwater prawn Macrobrachium rosenbergii (De Man) postlarvae (PL30). Immune response (total haemocyte count and prophenoloxidase activity) was also assessed by subjecting postlarvae to a challenge test against Aeromonas hydrophila (Chester) for 14 days. Iso‐nitrogenous and iso‐lipidic test diets were prepared using a fishmeal‐based‐positive control diet (D0) and four basal diets with inclusion levels of 2% (D2), 4% (D4), 6% (D6) and 8% (D8) C. vulgaris. Postlarvae of M. rosenbergii were randomly stocked (mean initial body weight of 0.19 ± 0.02 g) in 30‐L tanks in three replicates per dietary treatment for evaluation of growth performance. Another set of postlarvae (mean initial body weight of 1.25 ± 0.02 g) was randomly distributed in 95‐L tanks in three replicates per dietary treatment for the assessment of immune response. Results showed that specific growth rate was significantly higher (P \u3c 0.05) in postlarvae fed D4 and D6. Variations in values for carcass protein, lipid, moisture and ash were also evident. Postlarvae fed diets with Chlorella showed increased prophenol oxidase activity and total haemocyte counts. Moreover, survival rate after challenge with A. hydrophila was significantly increased (P \u3c 0.05). Inclusion of C. vulgaris in diets enhanced immune response and resistance of M. rosenbergii postlarvae against A. hydrophila infection