Botany and Plant Science

The response of an organism or its part is termed 'positive' if the growth is towards the stimulus or 'negative' if the growth is away from the stimulus. An example of chemotropic movement can be seen during the growth of the pollen tube, where growth is always towards the ovules.

Stigma serves as the receptive structure for pollens.

Chemotactic movement is performed by pollen tube towards embryo sac.

A pollen tube usually enters the embryo sac through one of the synergids.

This is the characteristic of angiosperms, and not gymnosperms. Here, the xylem is made up of xylem parenchyma, tracheids and fibres only.

There are two forms of polyembryony with respect to the origin of the embryos: simple, due to the fertilisation of several eggs and cleavage, and due to the splitting of products of zygote. This is common in pinus.

Each microsporophyll has two attached microsporangia. Microsporangia are organs that contain microsporocytes (immature pollen grains).

Duramen is the name given by botanists to the central wood or heart wood in a tree trunk.

Pollination in Cycas occurs at three celled stage (prothalial cell, generative cell and a tube cell).

Double fertilisation is a complex fertilisation mechanism of flowering plants (angiosperms). This process involves the joining of a female gametophyte (megagametophyte, also called the embryo sac) with two male gametes (sperm). It occurs in angiosperms.

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Potatoes are underground stem tubers. Underground stems are modified plant structures that derive from stem tissue but exist under the soil surface.

Each androcyte metamorphoses into a coiled (2-3), multi-flagellate and multiciliate antherozoid or spermatozoid.

In open vascular bundles, a layer of cambium will be present between the xylem and phloem. This enables secondary growth in it.