Pollen tube growth is one of the most fascinating—and essential—phenomena in the life cycle of flowering plants. After a compatible interaction between pollen grains and the stigma surface, the pollen germinates and forms the pollen tube, which grows through the stigma, style, and transmitting tract to deliver the sperm cells to the ovule."
2) Although pollens of many species germinate in simple aqueous media, stigmas do not provide satisfactory sites for the germination of most foreign pollen... Stigmas not only provide the proper conditions for the germination of pollen from their particular species, they actively inhibit the germination of pollen of many unrelated species.
Answer: An essay is a common type of academic writing that you'll likely be asked to do in multiple classes. Before you start writing your essay, make sure you understand the details of the assignment so that you know how to approach the essay and what your focus should be. Once you've chosen a topic, do some research and narrow down the main argument(s) you'd like to make. From there, you'll need to write an outline and flesh out your essay, which should consist of an introduction, body, and conclusion. After your essay is drafted, spend some time revising it to ensure your writing is as strong as possible.
Vascular plants<span> have two distinct organ systems: a </span>shoot<span>system and a </span>root<span> system. The </span>shoot<span> system consists of two portions: the vegetative (non-</span>reproductive<span>) parts of the plant, such as the leaves and the stems; and the </span>reproductive<span> parts of the plant, which include flowers and fruits.</span>
Stem cells<span> are a class of undifferentiated </span>cells<span> that are able to differentiate into specialized </span>cell<span> types. Commonly, </span>stem cells<span> come from two main sources: Embryos formed during the blastocyst phase of embryological development (embryonic </span>stem cells<span>) and. Adult tissue (adult </span>stem cells<span>).
hope this helps!</span>
I believe it would be number 4
