Lab Act 7 Plant Development Flashcards
modified leaves that protect the reproductive structures
Sepals and petals
The _______, which are modified leaves, form the outermost circle–or whorl. Collectively the ——- form the ______. Find the place where the —— attaches to the base of the flower. This is the _______. The petals are found just inside the sepals and the whorl of petals is called the _______.
sepals;
calyx;
receptacle;
corolla
______ are flowers whose parts occur in 3 or multiples of 3. __________ are flowers whose parts occur in 4 or 5 or multiples thereof.
Gumamela flowers are therefore…
Monocots;
Dicots
Dicots
What do you notice about the number of sepals and petals?
They are equal
Inside the corolla is a circle of ______. These are the male reproductive organs, each consisting of an ______ at the tip supported by a tubelike ______. _______ found inside the anther are the male gametophytes.
stamens;
anther;
filament;
Pollen grains
Under the stereomicroscope, the gumamela (Hibiscus spp.) stamen shows an elongated, lobed anther with a slightly rough texture, covered in fine, yellow pollen grains. The filament is long and slender, supporting the anther at the top. The pollen grains appear as tiny, round, and powdery structures, clumped together, indicating their readiness for pollination.
The pollen grains are formed from microspores in the ______.
pollen sacs
The female reproductive organ–or ______–is located in the center of the flower. The top portion of the —— is the _______. The —— is usually sticky and is where the pollen grains collect. The _____ is the stalk-like structure that supports the stigma. The enlarged structure at the base of the carpel is the ______. _______ within the ovary produce the female gametophytes.
carpel;
stigma;
style;
ovary;
Ovules
The stigma is supported by the style to improve its chances of catching pollen. Being elevated helps it come into contact with pollinators like insects or be exposed to wind for pollen transfer. The style also plays a role in filtering pollen, allowing only compatible and competent ones to grow pollen tubes and reach the ovary for fertilization.
The ovules develop into hollow compartments called ______. The outer layers of the ovule surround the ______. This sac is the female gametophyte and this is where the egg is located.
locules;
embryo sac
Stain used to view the ovules
methylene blue stain
Fertilization in angiosperms begins when a pollen grain lands on the stigma and absorbs moisture which triggers germination. A pollen tube emerges and grows down the style, guided by chemical signals from the ovule. Inside the tube, the ________ directs growth, while the two sperm nuclei travel toward the embryo sac in the ovary. Upon reaching the micropyle, one sperm nucleus fuses with the egg cell, forming a zygote, while the other fuses with two polar nuclei, creating the endosperm. This double fertilization ensures both embryo and nutrient-rich endosperm development, leading to seed and fruit formation.
tube nucleus
The _____ is a matured ovule and the final product of angiosperm reproduction.
seed
The ______ is a scar-like structure on the seed coat that marks the spot where the seed was attached to the ovary wall via the funiculus (seed stalk). It represents the point of connection between the developing seed and the parent plant, allowing the transfer of nutrients during seed formation.
hilum
The ______ is a tiny opening near the hilum that serves as the entry point for the pollen tube during fertilization, allowing sperm cells to reach the ovule. After fertilization, it remains as a small pore in the seed coat, facilitating water absorption during germination, which is crucial for activating metabolic processes needed for seed growth.
micropyle
Would you expect all seeds to have a hilum and a micropyle?
No, not all seeds will have a visible hilum and micropyle, but most do, as they are essential structures in seed development. The hilum marks the attachment point to the ovary, and the micropyle is where the pollen tube enters for fertilization. However, in some seeds, these features may become less distinct due to modifications in seed coat structure or dispersal adaptations, especially in seeds with highly specialized germination strategies.
After soaking overnight, the seed becomes swollen and softer as it absorbs water through the micropyle, triggering the initial stages of germination. The seed coat appears looser or wrinkled compared to the dry seed, which is hard and shrunken. Internally, the embryo becomes more turgid highlighting its increase in metabolic activity, preparing the seed for sprouting. The epicotyl was also observed to be much longer in the wet seeds.
The absorbed water rehydrates the seed, activating enzymes that break down stored nutrients in the cotyledons to support early growth. This process, known as _______, causes the seed to swell as water fills its cells, softening the seed coat and increasing internal pressure. These changes prepare the embryo for germination, enabling cell expansion and eventually, the radicle emerges.
imbibition
The _______ are large, fleshy, and smooth structures that make up most of the seed’s mass. They appear pale white after the testa was removed and they also feel soft due to water absorption. These seed leaves store nutrients, primarily starch, which will be used to support the seedling’s growth until it can photosynthesize independently.
cotyledons
The cotyledons serve as the seed’s nutrient storage organs, providing essential starches, proteins, and enzymes to support the early growth of the embryo. During germination, they supply energy until the developing seedling can produce its food through photosynthesis. In some plants, cotyledons may also emerge above the soil and function as the first leaves.
The epicotyl, often called the _______, consists of two, tiny leaves which enclose the terminal bud of the future plant. Below the epicotyl is the _______, the embryonic stem. The ______ is the embryonic root.
Remember that starch turns ________ in the presence of iodine.
plumule;
hypocotyl;
radicle;
purple or blue-black
We can hypothesize that the ________ contain the greatest amount of starch, as they serve as the primary nutrient storage organs for the developing seedling. If iodine is applied, the ——– will turn a deep blue-black, indicating a high starch content.
cotyledons
The cotyledons store starch as an energy reserve to support the early growth of the embryo before it can photosynthesize. The strong blue-black reaction with iodine will indicate a high starch concentration, which is gradually broken down into simple sugars by enzymes during germination. In contrast, the testa, epicotyl, and hypocotyl contain little to no stored starch, as their primary functions are protection, shoot development, and structural support rather than nutrient storage.
Examine an ear of corn. Is this the product of a single flower or a group of flowers?
group of flowers
Each kernel on the cob develops from an individual ovule within a separate flower in the inflorescence. These flowers are arranged along the cob, and after successful pollination, each forms a seed (kernel), making the ear of corn a multiple-fruit structure derived from many flowers.
The _______ is the point where the corn silk, which is the style of the flower, was once attached to the ovule. Each kernel develops from an individual flower, and its silk served as the pathway for pollen to travel down to fertilize the ovule. Once fertilization occurs and the kernel matures, the silk dries up and detaches, leaving behind the silk scar near the top of the grain.
silk scar
A corn silk represents a greatly elongated style ending in the stigma. It is attached to an individual ovary.
If an ear of corn had 250 grains, how many corn silks would there have been?
250 grains would have 250 corn silks, one for each fertilized ovule as they are individual flowers.
Each kernel on an ear of corn develops from a separate flower within the inflorescence, and each flower has its own silk that connects the stigma to the ovary. For fertilization to occur, pollen must land on the stigma of each silk, travel down the style, and reach the ovule inside the ovary. Since there are 250 grains, this means 250 individual flowers were fertilized, each originally having one corn silk, resulting in a total of 250 silks.
Would you expect to find a hilum and micropyle in the corn grain?
No, a corn grain (kernel) is a caryopsis, a type of fruit where the seed coat is fused with the fruit wall (pericarp), making structures like the hilum and micropyle less distinct or not externally visible. Unlike legumes, where the seed separates cleanly from the fruit, the corn kernel remains encased, so while the hilum and micropyle exist at a microscopic level, they are not easily identifiable on the grain’s surface. Instead, the most noticeable features are the germ (embryo) and the starchy endosperm, which provide energy for germination.
In corn, the _______ corresponds to the stalk of the bean’s flower. It is the pathway through which the grain receives nourishment.
point of attachment
The endosperm will turn blue-black if iodine is added which indicates the presence of starch.
Food in the corn grain is stored primarily in the form of starch, which serves as an energy source for the developing embryo during germination.
