I Equisetum horsetail sporophyte with whorled branches, reduced leaves, and a terminal cone; magnification x 0. J Cycas seed plant sporophyte showing leaves and terminal cone with seeds; magnification x 0. Origin of land plants.
New York: J. Wiley and Sons, All rights reserved. Part B: courtesy of M. Feist, University of Montpellier. Coleochaete orbicularis. Both the gametophyte and the background are bright green.
The gametophyte has an irregular circular shape and a scalloped edge. It is divided into many box-like segments cells , each with a visible, round nucleus inside. Panel b shows a Chara gametophyte. The organism has branching, tendril-like leaves reaching from a primary stalk. The green leaves are punctuated with small, round, yellow structures. A green liverwort gametophyte, In panel c, is protruding from the soil. Its four primary stems each diverge into two halves and then branch again at their termini, so that each has a forked end.
Panel d shows a hornwort gametophyte. Each green stem resembles a single blade of grass. Panel e shows moss gametophytes with sporophytes protruding from the ground. The gametophytes have small green leaves, and the sporophytes are thin, unbranched, brown stalks. Each sporophyte has a fluorescent orange, oviform capsule called a sporangia perched on top of its stalk. Panel f shows six clubmoss sporophytes emanating from the ground.
Some stand vertically out of the soil, and some curve or have fallen horizontally. They have many stiff, protruding, spine-like, green leaves. The sporangia are small yellow balls at the base of the leaves. Panel g shows fern sporophytes with many stems covered with small, elongated, symmetrical green leaves. Panel h shows a whisk fern sporophyte with long, straight, green stems beaded with yellow, round synangia along their lengths.
In panel i, a horsetail sporophyte is shown. It has a single long stem, which is surrounded by a skirt of green leaves at its base and an elongated, yellow cone at the top. In Panel j, a large Cycas seed plant sporophyte is shown. Long fronds emanate upwards from the plant's trunk, and in the center of them there is a large mass called the cone. Panel a is a photomicrograph of a gametophyte of a microscopic green alga called Coleochaete orbicularis.
Most living things depend on photosynthetic cells to manufacture the complex organic molecules they require as a source of energy. Photosynthetic cells are quite diverse and include cells found in green plants, phytoplankton, and cyanobacteria. During the process of photosynthesis, cells use carbon dioxide and energy from the Sun to make sugar molecules and oxygen. These sugar molecules are the basis for more complex molecules made by the photosynthetic cell, such as glucose.
Then, via respiration processes, cells use oxygen and glucose to synthesize energy-rich carrier molecules, such as ATP, and carbon dioxide is produced as a waste product. Therefore, the synthesis of glucose and its breakdown by cells are opposing processes. Figure 2 2 in the sky represents the process of photosynthesis. Two arrows are directed outwards from the trees towards the atmosphere. One represents the production of biomass in the trees, and the other represents the production of atmospheric carbon dioxide CO 2.
Arrows emanating from a tree's roots point to two molecular structures: inorganic carbon and organic carbon, which may decompose into inorganic carbon.
Inorganic carbon and organic carbon are stored in the soil. This CO2 can return to the atmosphere or enter rivers; alternatively, it can react with soil minerals to form inorganic dissolved carbonates that remain stored in soils or are exported to rivers. B The transformations of organic to inorganic carbon through decomposition and photosynthesis continue in rivers; here, CO2 will re-exchange with the atmosphere degassing or be converted to dissolved carbonates.
These carbonates do not exchange with the atmosphere and are mainly exported to the coastal ocean. Organic carbon is also exported to the ocean or stored in flood plains. C In the coastal ocean, photosynthesis, decomposition, and re-exchanging of CO2 with the atmosphere still continue. Solid organic carbon e. The reactions that make up the process of photosynthesis can be divided into light-dependent reactions, which take place in the thylakoids, and light-independent reactions also known as dark reactions or the Calvin cycle , which take place in the stroma.
Understanding what the inside of a chloroplast looks like is key to visualizing where the different reactions of photosynthesis occur. Surrounding the chloroplast is a double membrane, consisting of an outer membrane and an inner membrane. This is similar in structure to the double membrane of mitochondria.
The light-independent reactions of photosynthesis take place within the stroma. The interior of the chloroplast contains another membrane—the thylakoid membrane—which is folded to form numerous connected stacks of discs. Each disc is a thylakoid and each stack is a granum pl.
The light-dependent reactions of photosynthesis take place within the thylakoids. These reactions occur when the pigment chlorophyll, located within the thylakoid membranes, captures energy from the sun photons to initiate the breakdown of water molecules. These two energy-storing molecules are then used in the light-independent reactions.
Within chloroplasts, chlorophyll is the pigment that absorbs sunlight. It is stored in the thylakoid membranes in protein complexes called photosystem I and photosystem II. The series of light-dependent reactions begins when sunlight hits a molecule of chlorophyll, located in photosystem II. This excites an electron, which leaves the chlorophyll molecule and travels along the thylakoid membrane via a series of carrier proteins known as the electron transport chain.
Each water molecule breaks down into two hydrogen H atoms and one oxygen O atom. The oxygen is released as a waste product—oxygen atoms from disassembled water molecules join up in pairs to form oxygen gas O 2. The hydrogen ions build up in high concentration in the lumen of the thylakoid. Save Cancel. Share Cancel. Revoke Cancel. Flag Inappropriate The Content is. Flag Content Cancel. Delete Content. Delete Cancel. The chloroplast is involved in both stages of photosynthesis.
The light reaction takes place in the thylakoid discs. There, water H 2 0 is oxidized, and oxygen O 2 is released. The dark reaction occurs outside of the thylakoids.
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