Morphology of Flowering Plants Test - 10

Stilt roots occur in sugarcane. These are adventitious support roots that are common among mangroves.
They grow down from lateral branches, branching in the soil. Stilt roots arise from the first few nodes of the stem.

Stilt roots in Sugar cane:

The lateral branches in the Banyan Tree grow vertically downward into the soil and act as pillars. Prop or pillar or columnar roots are pillar-like roots that give extra mechanical support to heavy stem branches.

Growth of taproots is towards gravity.
Typically, a taproot is very thick. It is tapering in shape and grows directly downward into the soil towards the force of gravity.

Phyllode is leaf modification.
Example: Australian Acacia and Parkinsonia

The inflorescence is a collection of flowers in a particular branching pattern that does not contain full-size leaves among the flowers.

An edible inflorescence is  Brassica oleracea.

• B. oleracea is a tall biennial plant, forming a stout rosette of large leaves in the first year, the leaves being fleshier and thicker than those of other species of Brassica, adaptations to store water and nutrients in its difficult growing environment.
• In its second year, the stored nutrients are used to produce a flower spike.

• Spinose structures of plants are hard with sharp, stiff ends and perform the functions of deterring animals from the plants. These are either thorns, spines, or prickles.
• However, unlike thorns that are derived from the shoots and spines that are derived from leaves, prickles are derived from the epidermis and thus, can be found anywhere on the plant. The prickles of roses are exogenous in origin. 

Functions of Stem:

• It supports and holds leaves, flowers, and fruits.
• The stem allows the leaves to arrange in a way that they are able to receive direct sunlight in order to efficiently perform photosynthesis. The arrangement and position of leaves also allow for gas exchange.
• The xylem and phloem present in the vascular bundles of stems conduct water and minerals across the plant.
• Stems bear flowers and fruits in a position that facilitates the processes of pollination, fertilization, and dispersion of seeds.
• Some stems undergo modification to store food and water.
  Example: Succulents
• Few green stems contain chloroplasts and are capable of carrying out photosynthesis as well.
• Some stems are modified to carry out vegetative propagation which is a form of asexual reproduction seen in plants.

Pitcher of Nepenthes is leaf modification that serves as a device of insect trap to fulfill the mineral requirement of the plant.
The pitcher is actually a swelling of the mid-vein in the leaf. Insects are attracted to this because of nectar secretions and coloration.

Illustration of Pitcher of Nepenthes:

Plant make their own food in the presence of light as well as the exchange of gases also takes place.

Option A: The arrangement of veins on the leaves is known as venation.

Option B: Vernation is the phenomenon of the arrangement of leaves in the bud.

Option C: The arrangement of the flowers on a plant is known as Inflorescence.

Option D: The arrangement of leaves on the stem branches is known as phyllotaxy. Alternate, opposite, whorled, and basal are different arrangements of leaves on the stem.

Hence, option D is correct.

• Victoria is a genus of water-lilies, in the plant family Nymphaeaceae, with very large green leaves that lie flat on the water's surface.
• Victoria amazonica has a leaf that is up to 3 metres (9.8 ft) in diameter, on a stalk up to 8 metres (26 ft) in length. The genus name was given in honour of Queen Victoria of the United Kingdom.

The occurrence of more than one type of leaves is called heterophylly.

Semi-aquatic plants show heterophylly.
They have 2 different types:
(i) Underwater leaves are thin and lack cuticle and stomata.
(ii) Aerial leaves are thick and have cuticles and stomata.

Example of a semi-aquatic plant showing heterophylly:

Cyathium inflorescence is found in Euphorbia. A cyathium is one of the specialized pseudanthia forming the inflorescence of plants.

Corymb and umbel has same inflorescence i.e. racemose inflorescence and rest of all belongs to different inflorescence.

Zig-zag development of flower on inflorescence axis is Scorpioid cyme. Secondary buds develop alternately on the stem in a scorpioid cyme.

Cyathium is a special kind of inflorescence found in Euphorbia.
The involucre encloses a single female flower (reduced to a pistil) in the center, seated on a comparatively long stalk, and a number of male flowers (each reduced to solitary stamen around this, seated on short stalks).

Lotus (Nelumbo Nucifera Gaertn) is the National Flower of India. It is a sacred flower and occupies a unique position in the art and mythology of ancient India and has been an auspicious symbol of Indian culture since time immemorial.

In a flower, the arrangement of sepals and petals with respect to each other is called aestivation.

Glumes represent bracts.

► Glumes are a basal, membranous, outer sterile husk or bract in the flowers of grasses (Poaceae) and sedges (Cyperaceae).

► A bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis, or cone scale.
Bracts are often different from foliage leaves. They may be smaller, larger, or of a different colour, shape, or texture. Typically, they also look different from the parts of the flower, such as the petals or sepals.

Parts of a single grass spikelet, consisting of two glumes, four fertile florets, with one additional central floret that may or may not be sterile​:

• In Didynamous condition, related to androecium, stamens occur in two pairs, a long pair, and a shorter pair.
• The stamens in a flower are collectively known as the androecium. The androecium in various species of plants form a great variety of patterns, some of them highly complex.

Stamens attached to petals are epipetalous. The stamens in a flower are collectively called the androecium.

The thalamus or the receptacle is the condensed structure on the pedicle from which the floral organs arise. The thalamus typically has the nodes and internodes but the internodes are highly condensed or reduced. 

(A) Mother axis is the branch that bears the inflorescence or the flower.

(B) Thalamus (also called torus) is the axis of the floral shoot which is the direct prolongation of the pedicel and bears four sets of floral members.

(C) Root is the vegetative structure that arises from the radicle.

(D) Pedicel is the stalk that has thalamus at the end. It bears the flowers. It is attached to the mother axis.

Hence, option B is correct.

The androecium is the third whorl of a flower whose individual unit is called the stamen. It is the male reproductive organ whorl.

(A) Anthers are the parts of the stamen in which pollen grains are formed.
(B) Stamens are the male reproductive structures, collectively called the androecium.
(C) Filaments are the parts of stamens that connect the anthers to the thalamus.
(D) Tepals are the units of the whorl called the perianth.

Hence the correct answer is 'Stamens'

► The condition of stamens in which the stamens are united in a single bundle or group is called monadelphous. It is seen in Hibiscus.

► Polyadelphous is the condition in which stamens are united to form more than two bundles. It is seen in Ricinus.

Syncarpous gynoecium has two or more fused carpels. Flowers that bear a gynoecium but no androecium are called carpellate.
If a gynoecium has multiple carpels fused into a single structure, it is syncarpous.

A typical flower that has an ovary placed superior with respect to the other floral organs is called hypogynous. The other floral organs are attached below the ovary to the receptacle.
Example: China rose, mustard, Datura.

The part of the ovary where the funiculus attaches is referred to as the placenta.

In flowering plants, placentation occurs where the ovules are attached inside the ovary. 

The pappus is the modified calyx, the part of an individual floret, that surrounds the base of the corolla tube in flower heads of the plant family Asteraceae.

• Arrangement of ovules in the ovary is placentation.
• In flowering plants, placentation occurs where the ovules are attached inside the ovary.
• The ovules inside a flower's ovary are attached via funiculi, the plant part equivalent to an umbilical cord. The part of the ovary where the funiculus attaches is referred to as the placenta.