Understanding Nutritive Tissue for Embryo Growth

The question asks about the tissue that provides nourishment to a growing embryo, specifically within the context of plant reproduction and seed development. Understanding the function of different parts of the flower and developing seed is key to answering this.

Analyzing the Options for Embryo Nutrition

Option 1: Ovule

The ovule is a structure in flowering plants that contains the female gamete (egg cell) and, after fertilization, develops into a seed. While the ovule contains the structures that contribute to the seed, including the nutritive tissue, the ovule itself is not the direct source of nutrition for the growing embryo.

Option 2: Ovary

The ovary is part of the pistil (female reproductive organ) of a flower and contains the ovules. After fertilization, the ovary typically develops into the fruit. The fruit's function is primarily seed dispersal, and the ovary tissue itself does not directly nourish the embryo developing inside the seed.

Option 3: Endosperm

The endosperm is a tissue produced inside the seeds of most flowering plants around the time of fertilization. It is triploid (\(3n\)) in many species, formed by the fusion of a male gamete with the polar nuclei in the embryo sac. The primary function of the endosperm is to store food, such as starch, oils, and proteins. This stored food is then utilized by the growing embryo during its development and sometimes during germination.

Option 4: Zygote

The zygote is the diploid cell formed by the fusion of the male gamete and the egg cell. The zygote is the very first cell of the new sporophyte generation, and it develops into the embryo. Therefore, the zygote is the growing embryo, not the tissue that provides nutrition to it.

Why Endosperm Serves as Nutritive Tissue

During the process of double fertilization in flowering plants, one male gamete fuses with the egg cell to form the diploid zygote, and the other male gamete fuses with the polar nuclei to form the primary endosperm nucleus, which typically develops into the triploid endosperm. This evolutionary development ensures that a dedicated tissue exists within the seed specifically for storing the energy and nutrients required by the developing embryo. In many plants (like wheat, maize, rice), the mature seed retains a significant amount of endosperm, while in others (like peas, beans, groundnuts), the endosperm nutrients are absorbed by the cotyledons of the embryo during seed development, and the mature seed lacks endosperm.

Revision Table: Key Terms in Seed Development

Additional Information on Seed Nutrition

The presence and extent of endosperm in a mature seed vary among different plant species. Seeds with a prominent endosperm are called albuminous or endospermic seeds (e.g., cereals, castor). In these seeds, the endosperm remains as the primary storage tissue. Seeds where the endosperm is completely absorbed by the developing embryo, and nutrients are stored in the cotyledons, are called non-albuminous or non-endospermic seeds (e.g., legumes, groundnuts). Regardless of whether the stored food is in the endosperm or the cotyledons, its fundamental role is to provide energy and building blocks for the embryo's growth during development within the seed and during germination before the seedling can perform photosynthesis.