Salinity is a growing problem affecting soils and agriculture in many parts of the world. The presence of salt in plant cells disrupts many basic metabolic processes, contributing to severe negative effects on plant development and growth. This review focuses on the effects of salinity on chloroplasts, including the structures and function of these organelles. Chloroplasts house various important biochemical reactions, including photosynthesis, most of which are considered essential for plant survival. Salinity can affect these reactions in a number of ways, for example, by changing the chloroplast size, number, lamellar organization, lipid and starch accumulation, and interfering with cross-membrane transportation. Research has shown that maintenance of the normal chloroplast physiology is necessary for the survival of the entire plant. Many plant species have evolved different mechanisms to withstand the harmful effects of salt-induced toxicity on their chloroplasts and its machinery. The differences depend on the plant species and growth stage and can be quite different between salt-sensitive (glycophyte) and salt-tolerant (halophyte) plants. Salt stress tolerance is a complex trait, and many aspects of salt tolerance in plants are not entirely clear yet. In this review, we discuss the different mechanisms of salt stress tolerance in plants with a special focus on chloroplast structure and its functions, including the underlying differences between glycophytes and halophytes.

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In this study, four species of penaeid shrimp from Pakistan's inshore waters were studied. These were Penaeus penicillatus (Alcock), Penaeus merguiensis (de Man), Metapenaeus affinis (Milne Edwards) and Parapenaeopsis stylifera (Milne Edwards). During maturation, shrimp ovaries pass through a series of colour changes. The various colours observed in the ovaries of the four species of penaeid shrimps were translucent, white, cream, yellow, green-yellow, green-white, light green and dark green. The different type of oocytes observed in histological sections of the penaeid ovaries are as follows: chromatin nucleolar oocytes, perinucleolar oocytes, yolkless oocytes, yolky oocytes and oocytes with cortical bodies. The ovarian developmental stages recognized in these shrimps are: undeveloped, developing, nearly ripe, fully ripe, resorbing and resorbing/ developing. The ovarian developmental stages were similar in all the four species with the exception of the fully ripe stage. In the fully ripe stage of P. penicillatus and P. merguiensis, the cortical bodies were present at the periphery in two shapes; spherical as well as rod-like. On the other hand, in the fully ripe stage of M. affinis and P. stylifera, the cortical bodies were present only at the periphery and were only spherical. A relationship between colour of ovaries and histological stages of ovarian development was established. A female shrimp with a dark-green ovary is an indication of the readyto-spawn condition. In P. merguiensis and Penaeus penicillatus, respectively, 100% and 88.1% females with dark-green ovaries had oocytes with cortical bodies, whereas in M. affinis and P. stylifera, respectively, 50% and 28.6% females with dark-green ovaries had oocytes with cortical bodies.

The bay mussel Myfilits cdnlis ( Linnaeus) and the California sea mussel Mytilns calijornianus (Conrad), are polymorphic in color, shape and size. They are found intertidally on rocks, stones, or pilings and sometimes in deeper water down to 10 to 20 or 25 fathoms (Soot-Ryen, 1955). Mytilns cdnlis is found in several parts of the world and has been considered by some as a cosmopolite, although this opinion has been debated by Soot-Ryen (1955). M. cdnlis is native to the Pacific coast of North America, but may occur sympatrically with M. calijornianus which is common along the more exposed beaches in crashing waves and, indeed, occurs only where there is surf (Ricketts, Calvin, and Hedgpeth, 1968). Along the exposed beaches, the presence of M. ednlis appears to be related to the presence of fresh water streams, and at such places individuals of both species may occupy the same rocks. The two species are easy to distinguish except that very small specimens may be difficult to separate from one another.Mytilns edit I is is normally dioecious but rare hermaphroditic individuals can be found (Sagiura, 1962). While reviewing reproduction in molluscs, Eretter and Graham (1964) indicated that individuals of .17. calijornianus emitting sperms or eggs are true males and females and that there are no immature gametes of the opposite sex in the gonad. Both species broadcast their gametes and fertilization occurs externally.On the West coast of the United States, M. cdnlis commences spawning in late April or early May and continues until late August. Young (1942) indicated that in M. calijornianus, beginning in September, spawning gradually increases to reach a maximum in mid-winter and then declines to a minimum from May to August. Occasionally they will spawn in summer, but usually only to a limited extent.Both species have served as popular research material for embryological and physiological studies. However, nothing is known of their comparative cytogenetics. It is not known whether the forms of the two species are ecophenotypes or 1 Contribution No.

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