plant-life

Plant life

Despite the diversity that we see among plants, there is still unity that exists among them as reflected on how plants are constructed.

• • How they transport food
  • How they reproduce
  • How they grow
  • How their cells are organized

VASCULAR PLANTS

Any one of a number of plants with specialized vascular tissue

Composed of shoot and root systems

• ROOT SYSTEM – anchors the plants to the ground, to be able to absorb water and nutrients
• SHOOT SYSTEM – is the part that usually grows above the ground including the organs that may be associated with it such as the leaves, stems, and reproductive parts.

ROOT SYTEM

• The part of the plant that is anchored to the ground that serves for support and absorption of nutrients.
• They are underground structures that are devoid of nodes, internodes, and leaves.
• They are primarily for anchorage and absorption of nutrients.
• There are three types of roots:
  • Taproot
  • Fibrous
  • Adventitious

TAPROOT ( dominant central root)

• Usually bigger and grows deeper into the ground
• Usually found in dicot plants
  • DICOT PLANTS - the dicotyledons, also known as dicots, are one of the two groups into which all the flowering plants or angiosperms
• Composed of primary, secondary, and tertiary roots

FIBROUS ROOT

• Opposite of a taproot system
• Common in monocot plants
  • MONOCOT PLANTS – the monocotyledons commonly referred to as monocots, are grass and grass-like flowering plants (angiosperms)
• Located superficially on the ground
• Usually formed by thin, moderately branching roots growing from the stem

ADVENTITIOUS ROOT

• Arise from the other parts of the plant like in the main branches, twigs and leaves.
• Numerous on underground stems, such as rhizomes, corns, and tubers, and make it possible to vegetatively propagate many plants from stem or leaf cuttings.

ADVENTITIOUS ROOT

• Most roots are subterranean but there are also roots that can’t be found under the soil.
• Aerial roots – roots above the ground or non-subterranean roots
• Absorb moisture and nutrients
• The roots of more orchids

Specialized Roots

• Roots can be specialized to perform other functions than just anchorage and absorption.
• Some roots can function for storage
  • Roots of yam
  • Carrots
  • Sugar beets
  • Radish
• Other roots can also function for protection, support, reproduction, storage, and aeration.

Specialized Roots

• storage roots – specially modified for storage of starch and water
  • carrots, beets, and sweet potatoes
  • usually grow underground as protection from plant-eating animals
• Protection roots – usually grow underground as protection from plant-eating animals
  • carrots, beets, and sweet potatoes
• Aerating roots – rise above the ground, especially above water
  • are commonly seen in mangrove forests that grow along salt water

THE SHOOT SYSTEM

• Consists of the leaves and stems and other associated parts that are found above the ground.
• The leaves are arranged along the stems in such a way that each leaf gets enough sunlight.
• The flowers along with the fruits and seeds are also associated with shoot system.
• Roots are different from stems since they do not have nodes and internodes, which are common characteristics of stems.

• NODES – are points of attachment for leaves, aerial roots, and flowers
• INTERNODES – the stem region between two nodes

The Leaves

• Usually flattened, lateral, and green appendages on the stem of the plant
• Indispensable in the body since it functions as the food factory.
• This is where photosynthesis takes place since the green pigments, and other pigments abound in this organ.

• There are other anatomic parts associated with the leaf.
  • STOMATA – the primary breathing organ of the plant
  • CUTICLE and TRICHOMES – the hairy structure that prevents rapid loss of water and likewise protects the plants from predators

• Plants are photosynthetic organisms that use light energy, water, and carbon dioxide to produce organic foods for themselves and for other organisms.
• Leaves are the primary organs for this process due to the presence of chlorophyll pigments in their cells.
• Since water and minerals are indispensable in the physiology of plants, they have to be supplied by the transport system inside the plants.
• Remember that these substances are found in the soil and have to be transported upward from the roots to the tips of leaves.
• This is one of the tough jobs that plants have to do in order to survive!
• It has carry all these substances upward no matter how tall the plant is.

Nutrition in Plants

• All plants are autotrophic
  • AUTOTROPHS – organisms that make their own food
  • AUTOTROPHIC NUTRITION – production of own food

Nutrition in Plants

• Two types of autotrophic nutrition:
  1. PHOTOSYNTHESIS – a process of producing sugar from CO₂, and water using sunlight as the source of energy and chlorophyll for tapping light energy.
     • A method employed by all plants and relatively few other organisms.
  2. CHEMOSYNTHESIS – the production of organic compounds using energy derived from the oxidation of organic compounds such as hydrogen sulfide, ammonia and iron without the help of sunlight.
     • This is especially true in the deep-sea vents where sunlight can no longer penetrate, a favorable place for the existence of most chemosynthetic bacteria.

The stem

• The stem of the plant primarily serves as the main support system.
• It is usually composed of the main stem and branches.
• It is the part where the leaves are attached.
• Branching in plants may vary and is responsible for the plant form.

• Other structures associated with with stems:
  • lenticels - serve as the breathing organ
  • leaf scar - the scars left after a leaf fall
  • bundle scar - originated from the vascular bundles (xylem and phloem) that were cut off after a leaf falls.

Annual Rings

• The age of the tree may be estimated using the annual rings.
• Annual rings are circular structures that are visible in a cross section of a stem.
• The growing season that passed could also be traced from the annual rings.

Function of stem

• Some stems maybe specialized to perform other functions such as:
  • storage
  • reproduction
  • protection
  • photosynthesis

Examples of specialized stems for storage and reproduction:

• Gabi
• Ginger
• Potato
• Cactus - stems are modified for photosynthesis

Xylem and Phloem

• XYLEM - a type of tissue in vascular plants that transports water and some nutrients from the roots to the leaves.
• PHLOEM - the other type of transport tissue; it transports sucrose and other nutrients throughout the plant.

Conduction of Xylem Sap

• Xylem tissue in plants are primarily for the conduction of water and minerals from the roots, to all parts of the body.
• A number of concerted physio-chemical forces are responsible for this transport process.
  • root pressure
  • capillarity
  • pull of transpiration
  • adhesion
  • cohesion
• The greater is the pull of transpiration (loss of water in leaves), the faster is the movement of water upward.
  • water molecules tend to move from a region of greater water concentration to lesser, meaning from higher water potential to lower
• If there is a great loss of water in the leaf cells, water in the root cells will tend to rush into the leaf cells, making the transport process possible.
• During hot and dry seasons, there is always a gretaer tendency for plants to dry up, and wither due to excessive loss of water.

Translocation of Phloem Sap

• PHLOEM - the vessels where substances will pass through
• PHLOEM SAP - substances to be transported
• TRANSLOCATION – the transport process

REPRODUCTION IN PLANTS

• All plants undergo a life cycle which may differ in some groups but not in all.
• Plant life cycles are characterized by an alternations of generations
• ALTERNATION OF GENERATIONS - the diploid sporophyte gives rise to the haploid gametophyte.
  • SPOROPHYTE - the most dominant stage in higher plants and is the most abundant stage
  • GAMETOPHYTE - the most dominat stage in lower plants

ASEXUAL REPRODUCTION

• A type of reproduction that does not involve the fusion of gametes (sperm cell and egg cell)
• Results in genetically identical individuals since the offspring are produced by mitosis.
• VEGETATIVE REPRODUCTION - a very good example of asexual reproduction
• it is simply cutting a part of the adult plant and growing that part to become another plant
• examples: suckers, rhizomes, runners, tubers, other adventitious plantlets like katakataka
• CLONING - another method of asexual reproduction
  • Practiced in plant cultures like in a mass production of orchids
  • In this technology, orchids are cloned and grown by regenerating plant cells or tissues in a medium with nutrients and hormones.

• A type of reproduction that involves a complex life cycle in which a gamete with a single set of chromosomes combines with another to produce an organism composed of cells with two sets of chromosomes.
• The most common type of plant reproduction in Angiosperms (flowering plants) which is the most abudant group of plants.

• POLLINATION - is the process that brings about transfer of the pollen from the anther to the stigma of the female flower.
• Different types of pollinators:
  • wind
  • animals
  • insects
  • pollination can be done within the flower itself

LIFE SPAN OF PLANTS

• The length of time from the beginning of development to the death of a plant is called its life span.
• The life cycle, on the other hand, is the sequence of stages a plant goes through from seed germination to seed production of the mature plant.
• The life span of plants can be classified into:
  • perennial
  • annual
  • biennial

PERENNIAL PLANTS

• are those that live for several years or even after they have flowered
• most of them are woody plants and some are small flowering plants called herbaceous perennials

ANNUAL PLANTS

are those that short-lived, they only flower once and grow for only one growing season

BIENNIALS PLANTS

• are those that only complete their life cycle in two years
  • they store energy the first year
  • they flower the second year, and after which they die