Because most plants grow in soil, they exist in two worlds: above ground, where shoots obtain sunshine and CO2, and below ground, where roots obtain water and minerals. Plant colonization of the land was dependent on modifications that allowed early plants to collect nutrients from these two distinct environments.

Plants' algal ancestors absorbed water, minerals, and CO2 from the water in which they lived. Because each cell was near to the source of these chemicals, the transport was very straightforward in these algae. The first plants were nonvascular, producing photosynthetic shoots above the shallow fresh water in which they thrived.

Plants have evolved a broad range of shoot designs that allow each species to compete successfully for light absorption in the ecological niche it inhabits. The lengths and widths of stems, for example, as well as the branching pattern of shoots, are all architectural elements that influence light capture.

Stems act as support structures for leaves as well as conduits for water and nutrient transfer. Tall plants escape being shaded by surrounding plants. Most tall plants require thick stems to allow for increased vascular flow to and from the leaves as well as better mechanical support.

Vines are an exception, as they rely on other items (typically other plants) to provide support for their stems Stems are seen in woody plants, get thicker as a result of secondary growth (as shown in the attached image).

In general, branching allows plants to gather more sunlight for photosynthesis. Some species, however, such as The coconut palm does not branch. What is the source of all this?

What causes diversity in branching patterns? Plants have a limited lifespan. amount of energy to invest to shot development If the majority of that because more energy is expended in branching, there is less available for growing tall, and the chance of being shadowed by higher plants grows.

In contrast, if most of the energy is used on growing tall, the plants are not being harvested optimally.

Norway spruce phyllotaxy is developing. This SEM image, obtained from above a shoot tip, depicts the pattern of leaf emergence. The leaves are numbered from one to one hundred, with one being the youngest. (Some of the numbered leaves are obscured in the close-up.)

Phyllotaxy, or the arrangement of leaves on a stem, is an architectural element essential in light capture. The shoot apical meristem (as shown in the attached image) determines phyllotaxy and is unique to each species (as shown in the attached image).

A species may have one leaf per node (alternate, or spiral, phyllotaxy), two leaves per node (opposite phyllotaxy), or several leaves per node (whorled phyllotaxy).

The majority of angiosperms exhibit alternate phyllotaxy, with leaves arranged in an upward spiral around the stem, with each succeeding leaf emerging 137.5° from the preceding one. Why is it 137.5°? One theory is that this angle reduces the shadowing of the lower leaves by those above, specifically in places where there is a lot of direct sunlight.

Plant roots also develop mutually beneficial interactions with microbes, allowing the plant to more efficiently utilize soil nutrients. For example, the development of mutualistic connections termed mycorrhizae between roots and fungus was a key stage in plant colonization of land. Mycorrhizal hyphae provide a vast surface area for absorbing water and minerals, notably phosphate, to the root systems of many plants.

When resources are collected, they must be delivered to other sections of the plant that require them. In the next part, we will look at the mechanisms and pathways that allow resources like water, minerals, and carbohydrates to be transferred.

Typically, leaves act to collect sunlight and CO2. Stems act as support structures for leaves as well as conduits for long-distance water and nutrient delivery. Roots dig the earth for water and nutrients, therefore anchoring the entire plant.

Plant designs have evolved as a result of natural selection to improve resource acquisition in the ecological niche in which the plant species naturally resides.

The plasma membrane's selective permeability regulates the flow of chemicals into and out of cells. Plants have both active and passive transport systems. Plant tissues are divided into two parts: the apoplast (everything outside the cells' plasma membranes) and the symplast (everything inside the cells' plasma membranes).

The direction of water movement is determined by the water potential, which is a number that includes solute concentration and physical pressure. Plant cells become turgid as a result of osmotic water absorption and the resultant internal pressure.

Bulk flow, the movement of liquid in response to a pressure gradient, is used for long-distance transport. Bulk flow occurs in the xylem's tracheids and vessel elements, as well as the phloem's sieve-tube components. Transpiration propels water and mineral transfer from roots to shoots via the xylem. Water and minerals from the soil enter the plant through the root epidermis, traverse the root cortex, and finally enter the plant.

Water and minerals from the soil enter the plant through the root epidermis, traverse the root cortex, and enter the vascular cylinder via the endodermis' selectively permeable cells. The xylem sap is carried great distances by bulk flow from the vascular cylinder to the veins that branch throughout each leaf.

According to the cohesion-tension theory, xylem sap flow is caused by a water potential difference produced at the leaf end of the xylem by evaporation of water from leaf cells. Evaporation decreases the water potential at the air-water contact, resulting in the negative pressure that pushes water through the xylem.

Plants lose water vapor through transpiration. Wilting happens when the water lost via transpiration is not replenished by root absorption. When there is a lack of water, plants close their stomata. Plants might suffer irreversible damage if drought conditions persist for an extended period of time.

Stomata are the primary means by which plants lose water. When guard cells surrounding the stomatal hole take up K+, a stoma opens. Light, CO2, the drought hormone abscisic acid, and a circadian rhythm all influence stomatal opening and closure.

Plants that have adapted to dry conditions are known as xerophytes.

Adaptations to dry conditions include reduced leaves and CAM photosynthesis.

The major sugar sources are mature leaves, however storage organs might be seasonal sources. The primary sugar sinks are growing organs such as roots, stems, and fruits. Phloem transport is constantly directed from sugar source to sugar sink.

The active transport of sucrose is required for phloem loading.

Sucrose and H+ are transported when they diffuse along a gradient created by proton pumps. Sugar loading at the source and unloading at the sink maintain a pressure differential, which maintains phloem sap flowing through a sieve tube.

The symplast is quite active.

Plasmodesmata's permeability and number can vary. When dilated, they allow symplastic transport of proteins, RNAs, and other macromolecules across vast distances.

The phloem also transmits nerve-like electrical impulses that aid in the integration of whole-plant activity.