|Keywords (Extracted from title, table of contents and abstract of thesis)
groundnut, growth-regulators, drought, arachis hypogaea l, swat phalli-96, abscisic acid groundnut, growth-regulators, drought, arachis hypogaea l, swat phalli-96, abscisic acid
This research project investigated the physiological and biochemical basis of drought stress in groundnut (Arachis hypogaea L.) plants. The project was divided into two parts. In first part of the project, field experiments were conducted at three different locations in northern NWFP Pakistan having diverse agro-c1imatic conditions (Swat, Qaldara and Timargara) to evaluate the performance of various groundnut genotypes and varieties under drought stress conditions. Data was recorded on various morphological, yield and yield components. Statistical analysis of the data suggested that drought stress had a detrimental effect on the performance of the various genotypes and varieties under study. Among the tested genotypes and varieties, Swat Phalli-96 performed better when compared with the other genotypes and varieties under study.
In the second part of the research project, pot experiments were carried out to further evaluate the performance of groundnut variety Swat Phalli-96 (preliminary screened under field condition) under drought stress with or without foliar application of growth-regulators (abscisic acid (ABA), gibberellic acid (GA) and Indole-3-acetic acid (IAA) applied as seed treatment and as foliar spray at 10-4 M). A range of growth parameters (i.e., number of pods plant-l, kernel pod-1, shelling percent, 100-kernel weight, 20-pod length, sound mature kernel, haulm yield, days to flowering, maturity, plant stand and pod yield (kg plot-1) were measured from these plants. Furthermore, the pot experiments were used to investigate the proline contents as osmoprotectant and endogenous abscisic acid (ABA) level under drought stress. Drought stress significantly (p â‰¤ 0.05) reduced all the growth and yield parameters (i.e., relative water content (RWC), dry weight of root, stem, peg, number of pods plant-l, kernel pod-1, shelling percent, 100-kernel weight, 20-pod length, sound mature kernel, haulm yield, days to flowering, maturity, plant stand and pod yield (kg plot-1). Analysis of the data also indicated that gibberellic acid (GA) and Indole-3-acetic acid either applied as seed treatment or foliar spray had no significant (p â‰¤ 0.05) effect on various growth and yield parameters under drought stress condition but the foliar application of abscisic acid (AB A) (10-4 M) partially ameliorated the adverse effect of drought stress on growth and yield components. Exposure of plants to drought stress and abscisic acid (AB A) foliar application both resulted in elevated levels of endogenous ABA and proline, which presumably is involved in cell signaling processes to combat drought stress. The endogenous abscisic acid (ABA) in shoot showed early response to applied abscisic acid (ABA) than that of root abscisic acid (ABA). Plants exposed to water stress + abscisic acid (AB A) can tolerate drought in better way than that of exposed to water stress alone.
However, proline is unlikely to be the sole marker for abscisic acid (ABA) dependent drought tolerance in groundnut as minor increase in proline level had been observed following abscisic acid (ABA) application. But it appears that abscisic acid (ABA) acts as a signal (messenger) that induces a cascade of acclimation response in groundnut.