Rajasthan BoardEnglish MediumSTD 11 ScienceBIOLOGYMODEL PAPER 93 Marks
Question
Describe the important characteristics of gymnosperms.
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Answer
Characteristics of Gymnosperms: The gymnosperms (gymnos: naked, sperma: seeds) are plants in which the ovules are not enclosed by any ovary wall and remain exposed, both before and after fertilization. The seeds that develop post-fertilization are not covered, i.e. are naked. Gymnosperms include medium-sized trees or tall trees and shrubs. The roots are generally tap roots. Roots in some genera have a fungal association in the form of mycorrhiza while in some others small specialized roots called coralloid roots are associated with $N _2$ fixing cyanobacteria. The stems are unbranched (Cycas) or branched (Pinus, Cedrus). The leaves may be simple or compound. In Cycas, the pinnate leaves persist for a few years. The leaves in gymnosperms are well adapted to withstand extremes of temperature, humidity and wind. In conifers, the needle-like leaves reduce the surface area. Their thick cuticle and sunken stomata also help to reduce water loss.
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