Question

the woody covering causes sinking of seeds in water

Answer 1

Explanation:

Immature seeds (called ovules) each contain a minute, single-celled egg enclosed within a 7-celled embryo sac. The haploid (1n) egg is fertilized by a haploid (1n) sperm resulting in a diploid (2n) zygote that divides by mitosis into a minute, multicellular embryo within the developing seed. A second sperm unites with 2 haploid polar nuclei inside a binucleate cell called the endosperm mother cell which divides into a mass of nutritive tissue inside the seed. In most seeds the embryo is embedded in this endosperm tissue which provides sustenance to the embryo during germination. In exalbuminous seeds (found in many plants such as the legumes), the endosperm tissue is already absorbed by the time you examine a mature seed within the pod, and the 2 white fleshy halves in the seed are really the cotyledons (components of the embryo). The 2 sperm involved in the double fertilization process originated within the pollen tube that penetrated the embryo sac. The pollen grain (and pollen tube) come from the "male" organs (called anthers) on the same plant or different parental plants in a remarkable process known as pollination. Pollination is also accomplished by the wind (or water), and it may also involve insects in some of nature's most fascinating relationships between a plant and an animal. This is especially true of the amazing fig trees and their symbiotic wasps.

One of the important functions of seeds and fruits is dispersal; a mechanism to establish the embryo-bearing seeds in a suitable place away from their parental plants. There are 3 main mechanisms for seed and fruit dispersal: (1) Hitchhiking on animals, (2) Drifting in ocean or fresh water, and (3) Floating in the wind. This article concerns one of the most remarkable of all seed dispersal methods, riding the wind and air currents of the world.

Types Of Wind Dispersal:

Gliders

Parachutes

Helicopters (Whirlybirds)

Flutterer/Spinners

Cottony Seeds & Fruits

UbiquitousTumbleweed

Miscellaneous