GENERAL EFFECTS OF SALINITY ON PLANT GROWTH (Mostly NaCl)

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INTRODUCTION

The disposal of large amounts of gypsiferous water, generated in coal mining operations in the Mpumalanga Highveld region in South Africa, has become a problem of increasing importance. This water is unsuitable for direct uncontrolled discharge into watercourses where it may become a threat to the environment and a problem to potential users. There are several different approaches to this problem. One alternative approach currently being investigated is the use of these waters for the irrigation of agronomic crops and pastures. In this way, large amounts of waste water could become economically useful for irrigation.

LITERATURE SURVEY

This chapter deals with plant response to salinity in the root growth zone. A brief introduction is followed by the general literature which pertains mostly to the influences of NaCl-dominated salinity on plant growth. The influence of salinity on the morphological aspects of growth is first discussed, followed by the physiological responses of the possible sensitivity and tolerance mechanisms.

GROWTH RESPONSES

Plants differ in their ability to grow under saline conditions. Greenway & Munns (1980) suggested four groups of plant species according to their growth under saline conditions. They are halophytes, where growth is optimal under sodic and/or saline conditions; a few crop species termed halophylics, where growth is slightly stimulated by low salinity levels and two groups which are non-halophytes (glycophytes) that range from moderately salt-tolerant to salt-sensitive. Most crop species fall under the last two groups which are, however, not clearly defined.

Root growth

Generally root growth is affected less by salinity than is shoot growth. At low salinity it may not be influenced or may even show an increase. These observations are, however, mostly based on root dry mass; root length, which is important for nutrient and water uptake, has been shown to be a more sensitive parameter than root dry mass for the influence of salinity on root growth (Shalhevet, Huck & Schroeder, 1995).

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ACKNOWLEDGEMENTS
ABSTRACT
CHAPTER 1 INTRODUCTION
CHAPTER 2 LITERATURE SURVEY
2.1 INTRODUCTION
2.2 GENERAL EFFECTS OF SALINITY ON PLANT GROWTH (Mostly NaCl)
2.3 SULPHATE SALINITY
2.4. FACTORS THAT INFLUENCE SALT TOLERANCE
2.5 EVALUATION OF CROP SALT TOLERANCE
2.6 SALT TOLERANCE OF AGRONOMIC GROUPS
CHAPTER 3 EXPERIMENTAL MATERIALS AND METHODS
3.1 MATERIALS
3.2 METHODS
3.3 STATISTICAL ANALYSES
3.4 UNITS AND TERMS
CHAPTER 4 SEEDLING GROWTH AND CULTIVAR DIFFERENCES
4.1 INTRODUCTION
4.2 RESULTS AND DISCUSSION
4.3 CONCLUSION
CHAPTER 5 SEEDLING GROWTH WITH INCREASING CONCENTRATI MINE WATERS
5.1 INTRODUCTION
5.2 SAND CULTURE EXPERIMENTS
5.3 SOIL VERSUS SAND EXPERIMENT
5.4 DISCUSSION
5.5 SUMMARY AND CONCLUSIONS
CHAPTER 6 TOLERANCE TO GYPSIFEROUS MINE WATERS AT THE GERMINATION, SEEDLING AND VEGETATIVE GROWTH STAGES
6.1 INTRODUCTION
6.2 GERMINATION
6.3 VEGETATIVE GROWTH
6.4 CHEMICAL ANALYSES OF TOP GROWTH
6.5 COMPARISON OF THE SEEDLING AND VEGETATIVE GROWTH STAGE WITH GYPSIFEROUS MINE WATER
6.6 CONCLUSION
CHAPTER 7 GENERAL DISCUSSION AND CONCLUSIONS