xylem

Xylem is the complex tissue of plants, responsible for transporting water and other nutrients to the plants. Phloem is living tissue, responsible for transporting food and other organic materials.

Xylem consists of tracheids, vessels, parenchyma, and fibers.

Types of phloem – definition

• Sieve tubes: Transport sugars and nutrients up and down the plants in sieve cells.
• Companion cells: Controls the activity of sieve tube.
• Phloem parenchyma: Provides mechanical strength to the plant.
• Phloem fibres: Stores compound such as starch.

Although its primary function is transport of sugars, phloem may also contain cells that have a mechanical support function. Both cell types have a secondary cell wall and are therefore dead at maturity.

Introduction. Secondary walls are mainly found in tracheary elements (tracheids in seedless vascular plants and gymnosperms and vessels in angiosperms) and fibers in the primary xylem and the secondary xylem (wood) (Fig. 1).

All plant cells have a primary cell wall; only some plant cells have secondary walls. Secondary wall is impervious to water due to lignin: water can not flow in or out of a cell except when there is an opening. Cavities (openings) in the secondary wall, water flows through pits.

Primary memory is directly accessible by Processor/CPU. Secondary memory is not directly accessible by the CPU. The memory devices used for primary memory are semiconductor memories. The secondary memory devices are magnetic and optical memories.

Primary memory is also known as Main memory or Internal memory. Secondary memory is also known as External memory or Auxiliary memory. 7. Examples: RAM, ROM, Cache memory, PROM, EPROM, Registers etc. Examples: Hard Disk, Floppy Disk, Magnetic Tapes etc.

RAM (random access memory) and cache are both examples of a primary storage device. A primary storage device may also be referred to as internal memory, main memory, main storage, and primary memory.

Primary memory usually refers to Random Access Memory (RAM), while secondary storage refers to devices such as hard disk drives, solid state drives, removable “USB” drives, CDs, and DVDs.

Typical secondary storage devices include magnetic tape drives, magnetic disk drives, compact optical disk drives, and archival storage devices such as disk jukeboxes.

Primary storage in a form of magnetic memory, or core memory, core rope memory, thin-film memory and/or twistor memory. Tertiary (e.g. NCR CRAM) or off line storage in the form of magnetic cards. Magnetic tape was then often used for secondary storage.

In this case, primary storage typically refers to random access memory (RAM), while secondary storage refers to the computer’s internal hard drive. For this reason, RAM is used to store data loaded by active programs and the operating system.

Primary memory is the main memory of the computer system. Accessing data from primary memory is faster because it is an internal memory of the computer. Primary memory is expensive and is available in limited in size in a computer. Secondary memory is cheaper compared to primary memory.

→example:- hard disk, CD-ROM, DVD, etc. It is used for storage of the data in the computer. Computer may run without secondary memory. Slower than primary memories. These are magnetic and optical memories.

This is the storage that is inside your computer and has direct access to the CPU. It includes RAM and ROM. Primary storage is needed to boot up your computer. SECONDARY STORAGE. Secondary storage is still inside your computer but doesn’t have direct access the CPU.

External storage devices

• External HDDs and SSDs.
• Flash memory devices.
• Optical Storage Devices.
• Floppy Disks.
• Primary Storage: Random Access Memory (RAM)
• Secondary Storage: Hard Disk Drives (HDD) & Solid-State Drives (SSD)
• Hard Disk Drives (HDD)
• Solid-State Drives (SSD)

External Hard Drive. The storage capacity of storage devices varies from a few bytes to gigabytes. The three basic types of data storage devices are primary storage, secondary storage, and tertiary storage. Each device class of removable media type is associated with a single library.

A storage device is any type of computing hardware that is used for storing, porting or extracting data files and objects. Storage devices can hold and store information both temporarily and permanently. They may be internal or external to a computer, server or computing device.