Biological World

Comparison between Normal and Coralloid Root:   Normal root:   Coralloid root:   1. Develops from the radicle, tap root system   2. Geotropic   3. Such characters are absent   4. Such infection is absent     5. Root hairs are present   6. Cortex is smaller   7. Such division is absent       8. Secondary growth present   9. Main functions are: fixation of plant, absorption of water and mineral nutrients   1. Develops from the normal roots   2. Apogeotropic   3. Develops from the normal roots   4. Dichotomously branched and appears like coral   5. Gets infected with algae, bacteria   6. Cortex is wider in comparison   7. Due to presence of the algal zone in the cortex, it is differentiated into outer cortex and inner cortex   8. Xylem ver...

Significance of coralloid root Coralloid roots are a fascinating adaptation in certain plant species that enables them to thrive in nutrient-poor soils by forming a symbiotic relationship with nitrogen-fixing cyanobacteria. This type of root is found in Cycas . This unique root structure helps these plants access essential nitrogen, contributing to their survival and ecological significance.   Symbiotic relationship : Coralloid roots are primarily associated with a symbiotic relationship between the plant and nitrogen-fixing cyanobacteria, specifically species of the genus Nostoc. This relationship is mutualistic, benefiting both the plant and the cyanobacteria.   Nitrogen fixation : Cyanobacteria living within the coralloid roots are capable of fixing atmospheric nitrogen into a form that can be readily absorbed by the plant. This process provides the host plant with a vital source of nitrogen, an essential nutrient for plant growth.   Unique appearance : Corall...

  Coralloid roots : Coralloid roots, also known as "coral-like roots," are specialized root structures found in some plants, particularly certain species of cycads and gymnosperms. These roots have unique features and functions that set them apart from typical plant roots. Here are some important notes on coralloid roots: Structure : The transverse section of the coralloid root is similar to that of normal root and it can be differentiated into epidermis, cortex and vascular tissue. a. Epidermis : In young root, it is similar to normal root. However, in old root the outermost tissue is periderm. It consists of 2 to 5 layers of dead cells. b. Cortex : The cortex is wider in comparison with the normal root. A greenish algal zone is present almost in the middle of the cortex and divides it into outer cortex and inner cortex. The algal zone consists of loosely co blue green algae ( Anabaena cycadae, Nostoc punctiforme, Oscillatoria , Pseudomonas radicicola ) and som...

Transverse Section of Leaflet of Cycas Cycas is a perennial, slow-growing evergreen gymnospermic plant.  It looks like a palm tree. Its main plant body is sporophytic, diploid, dominant and can be differentiated into three parts – roots, stem and leaves. leaves are also produced in a crown at the apex of the stem. A single foliage leaf is pinnately compound. It is unipinnate and paripinnate. Each leaf has 80-100 pairs of leaflets which are arranged on both the sides of adaxial groove of the rachis in opposite or alternate manner.   The leaflets are tough, thick, and leathery. A transverse section of the leaflet of Cycas shows the following structures : (1) Cuticle: The upper surface of the leaf is covered with a thick cuticle. It serves to check excessive transpiration. (2) Epidermis : The leaflet is surrounded by an upper and lower epidermis. the single-layered epidermis is made up of thick-walled parenchymatous cells. both the lower and upper epidermis are covered external...

  Clam Connection  Clam Connection  একধরনের কোশ বিভাজন যা ব্যাসিডিওমাইসিটিস ছত্রাকে ডাইক্যারিওটিক অনুসূত্রে দেখা যায় । এখানে শীর্ষ কোশের পার্শ্ব প্রাচীর থেকে একটি বাঁকানো উপবৃদ্ধি শীর্ষকোশের তলার দিকে যুক্ত হয় । একটি ) নিউক্লিয়াস এই ক্ল্যাম্পে প্রবেশ করে বিভাজিত হয় , অন্য নিউক্লিয়াসটি শীর্ষ কোশ লম্বতলে বিভাজিত হয় । এরফলে ক্ল্যাম্পের উপরে শীর্ষ কোশে দুটি নিউক্লিয়াস থাকে এবং ক্ল্যাম্পের ভিতরে একটি নিউক্লিয়াস ও শীর্ষ কোশের তলায় অন্য নিউক্লিয়াসটি থাকে । ক্ল্যাম্পের গোড়াতে ব্যবধায় তৈরি হয় এবং ক্ল্যাম্পের পার্শ্বে শীর্ষকোশের প্রস্থে একটি ব্যবধায় তৈরি হয় ফলে দুটি কোশ দুটি নিউক্লিয়াস যুক্ত হয় । চিত্রঃব্যাসিডিওমাইসিটিসের ক্লাম্প কানেকশন । ভূমিকা  ঃ সব কোশেতে দুটি নিউক্লিয়াস যাতে থাকে তার ব্যবস্থা করা সেই সব অনুসূত্রে যেখানে নিউক্লিয়াস দুটি পাশাপাশি না থেকে উপর - নীচে থাকে !

Differences between Gymnosperms and Pteridophytes .  The plant bodies of pteridophytes are provided with well developed true roots , stems and leaves . They possess vascular or conducting tissues such as xylem and phloem and so they are known as vascular cryptogams. They never produced seeds at all. The plant bodies of gymnosperms are provided with true roots , stems , leaves and vascular bundles. Their seeds are exposed and remain in naked condition simply on the surface of the megasporophylls . The main points of differences between Gymnosperms and Pteridophytes are given below : ( 1 ) The majority of pteridophytes are homosporous whereas all gymnosperms are heterosporous . ( 2 ) The roots are adventitious in pteridophytes whereas in most of the gymnosperms , the roots are tap roots . ( 3 ) The stems are mostly underground rhizomes in most of the ferns , wheras in gymnosperms , the stems are aerial .  ( 4 ) The gymnospermous stems have a eustelic organisation whereas in the ...

Affinity of Gymnosperms with Pteridophytes :  The gymnosperms resemble the pteridophytes by the following features : (1) Both possess independent sporophytes which are differentiated into root , stem and leaves . Both the groups exhibit heterosporous life cycle . (2) The sporophytes possess a well developed vascular system such as xylem and phloem . The xylem in most of the members of groups lacks vessels and the phloem lacks companion cells . (3) Many Cycads resemble the ferns in possesing large compound leaves and the in the circinate ptyxis of the leaves . Dichotomous venation in Ginkgo  and ferns . (4) The female sex organs are archegonia in both the groups . (5) The male gametes of Cycads and Ginko are motile , like the pteridophytes .  (6) Many pteridophytes like Marselia,Salvinia , Azolla, Isoetes and Selaginella are heterosporous like the gymnosperms . ( 7 ) Some of the heterosporous pteridophytes possess one megaspore in the megasporangium , like the gymnosperms ...