Question

compare the reproductive organ and Reproduction of selaginella equisetu and pteris with proper diagram

Answer 1

Answer: Selaginella shows considerable variation in size, symmetry and morphology. Mostly they are herbaceous perennials, however, a few are annu­als (Selaginella pygmaea).

Majority are dorsiventral, prostrate and creeping (Fig. 7.45) on the sur­face (e.g., Selaginella kraussiana; S. pellidissima; S. chrysocaulis), some are radial and grow erect (e.g., S. rupestris; S. viridangula; S. selaginoides) and few are scandent (e.g., 5. willdenovii; 5. adunca) and climbers (5. alligans).

Selaginella Kraussiana

Most of the species of Selaginella grow on the ground in humid, shady habitats. A few species are xerophytic and grow in arid condi­tions on exposed rock surfaces (5. pilifera; S. lepidophylla). They have the ability to survive desiccation.

Resurrection Plant:

Some xerophytic species (e.g., S. lepidophylla, S. pilifera, 5. bryopteris) rolls up into a compact ball of seeming­ly dead leaves and stems during dry seasons, but unrolls to carry on normal activities when put in water. Such plants are commonly known as the “resurrection plants” and are often sold as curiosities.

Salient Features of Selaginella:

i. The sporophyte is herbaceous and the shoot is dorsiventral and radial and creeping or erect.

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ii. The leaves are small (microphyllous) and a ligule is present at the base of each leaf and sporophyll.

iii. Rhizophore is (a leafless structure where from roots arises) present in some species.

iv. Sporophylls are usually aggregated into strobili at the apices of the branch, hetero- sporous.

v. Heterothallic (dioecious) gametophytic pro­thalli.

vi. Antherozoids are biciliate.

Structure of Selaginella:

The Sporophyte:

The plant body of Selaginella is differentia­ted into well developed roots, stem and leaves.

Besides, some species also have rhizophore (Fig.7.46A).

Portion of Sporophyte and Enlarged Part of the Stem

Hieronymus (1902) divided the genus Selaginella into two sub-genera viz., Homoeophyllum and Heterophyllum on the basis of general structure of the plant body (Table 7.4).

Distinction between Homoeophyllum and Heterophyllum

Stem:

The stem is generally erect and radially con­structed in the subgenus Homoeophyllum. The species belonging to the subgenus Heterophy­llum are prostrate and dorsiventral. The bran­ching is dichotomous in the member of Homoeophyllum and somewhat lateral in Heterophyllum.

The anatomy of the mature stem is very dis­tinct and is differentiated into an outer epider­mis, middle cortex and centrally located stele (Fig. 7.47). The outer cell walls of the epidermis are cutinised. It is devoid of stomata and hairs. In many species there are several layers of thick- walled cells (hypodermis) beneath the epider­mis, which merge gradually with thin-walled chlorophyllous cells of the cortex.

The cortex is usually made up of compactly arranged angular parenchymatous cells without intercellular spaces. The most part of the cortex of xerophytic species viz., S. lepidophylla and 5. rupestris, is comprised of thick-walled sclerenchymatous cells.

There is much variation in the vascular cylinder among the different species of Selaginella. The number of stele varies from species to species and sometimes even in the same species. This is due to the dissection of the main stele. Young plants invariably show monostelic configuration.

T.S. of Selaginella Stem

In most species the creeping stem or pros­trate rhizome is protostelic. Species with radial symmetry may have a single, cylindrical proto- stele in the stem (monostelic e.g., S. spinulosa, S. flabellata), whereas dorsiventral species may have two (e.g., distelic e.g., S. kraussiana) or more vascular strands (12-16 steles) (polystelic e.g., S. laevigata) that are either circular or ribbon-shaped.

Explanation:

Answer 2

reproductive organs are those organs which are reproduce by after birth example bones and growth of the body....

if this is in plant then it is present in stem or growing regions that is apical, lateral, intercalary etc..

here apical is present in growing regions of stem and roots..

here intercalary is present in internodes and nodes of leaves....

here lateral is present alongside of stem

hope helpfullll..........