The adult, or sporophyte
, phase is the main phase of an angiosperm’s life cycle. As with gymnosperms, angiosperms are heterosporous. Therefore, they generate microspores, which will produce pollen grains as the male gametophytes, and megaspores, which will form an ovule that contains female gametophytes.
What does a pollen grain represent quizlet?
A pollen-producing male reproductive part of a flower
, consisting of a filament and an anther. A sac located at the tip of a flower’s stamen; contains male sporangia in which meiosis occurs to produce spores that form the male gametophytes, or pollen grains.
What life stage does a pollen grain represent?
The
male gametophyte
, the pollen grain, has a brief free-living stage while it is carried from plant to plant by wind, water, or animals.
What are the stages in pollen grain formation?
Two distinct and successive developmental phases,
microsporogenesis and microgametogenesis
, lead to the production of the mature microgametophytes. Microsporogenesis comprises the events which lead to the formation of the haploid unicellular microspores.
What plant generation does a pollen grain represent?
In flowering plants, the
gametophyte generation
takes place in a flower, which forms on the mature sporophyte plant. Each male gametophyte is just a few cells inside a grain of pollen. Each female gametophyte produces an egg inside an ovule.
Where does the pinecone fit into the life cycle?
The pine cone life cycle starts with a group of female strobili, called an
inflorescence
. Inside the scales, the seeds develop next to each other in the inflorescence. The pine cone grows as the seeds inside grow, protecting them from predators and harsh weather along the way.
What is the life cycle of gymnosperm?
The life cycle of a gymnosperm involves
alternation of generations, with a dominant sporophyte in which reduced male and female gametophytes reside
. All gymnosperms are heterosporous. The male and female reproductive organs can form in cones or strobili.
What do the pollen sacs produce?
pollen sac The structure in seed plants in which
pollen
is produced. In angiosperms there are usually four pollen sacs in each anther; they contain the microspore mother cells. In gymnosperms variable numbers of pollen sacs are borne on the microsporophylls that make up the male cone.
Where are the pollen sacs located on a Gymnosperm?
In most gymnosperms the male pollen cones, called microstrobili, contain reduced leaves called microsporophylls. Microsporangia, or pollen sacs, are borne on
the lower surfaces of the microsporophylls
.
What signifies that the mature pollen grain is the male gametophyte?
What portion of a germinated pollen grain tells you that it is the mature male gametophyte?
Presence of sperm
.
Which of these is contained in a pollen grain?
Each pollen grain contains
vegetative (non-reproductive) cells
(only a single cell in most flowering plants but several in other seed plants) and a generative (reproductive) cell. In flowering plants the vegetative tube cell produces the pollen tube, and the generative cell divides to form the two sperm nuclei.
How many cells are present in a mature pollen grain?
Mature pollen grains contain
two cells
: a generative cell and a pollen tube cell. The generative cell is contained within the larger pollen tube cell. Upon germination, the tube cell forms the pollen tube through which the generative cell migrates to enter the ovary.
What is a mature pollen grain?
Mature free pollen grains contain
starch grains and/or lipid droplets
. … In some plants, two-celled pollen grains are shed, i.e., pollen grains contain a generative cell and a vegetative cell at anthesis. Other plants shed three-celled pollen grains that contain a vegetative cell and two sperm cells.
Where do the pollen germinate naturally?
The pollen grains germinate naturally on
the stigma of compatible flower
. They develop pollen tubes that helps to deliver sperm nuclei inside the embryo sac where fertilization takes place.
What is the function of pollen grains?
Pollen grains carry male reproductive cells (gametes) in a plant and are haploid microgametophytes. Their main function is in
the transferring of the male gametes to their female counterparts
(ovules – female reproductive cells) in the embryo sac. It thereby facilitates sexual reproduction to occur in the plant.
What are the uses of pollen grains?
Pollen can be used to determine
pollination mechanisms, foraging resources, migration routes and source zones
of insects and other pollinators.
