Abstract
The experiment was carried out to determine the effects of heat stress on some growth parameters like shoot height, leaf area, fresh weight, dry weight as well as the accumulation of chlorophylls in Carica papaya. Seedlings of C. papaya were exposed to prior heat stress at 40 °C. A group of plants was placed in a Gallenkamp oven for four hours; another group of plants was placed in the oven for eight hours while the third group of plants was placed in a dark cupboard for the period of eight hours. Sampling was carried out at weekly intervals starting from seven days after treatment. Plants were randomly picked from each of the three treatments. Three replicates were used for each parameter. The results obtained from the study showed that there was an increment in the shoot height, leaf area, fresh weight and dry weight from the beginning to the end of the experimental period. However, the accumulation of chlorophylls did not follow a particular pattern. The analysis of variance carried out on the data obtained showed that heat stress had a significant effect on the petiole length, shoot height, leaf length, leaf width, leaf area, fresh weight and dry weight. Heat stress, however, did not produce a significant effect on the accumulation of chlorophylls a and b and total chlorophyll.
Highlights
Heat stress is often defined as the rise in temperature beyond a threshold level for a period of time sufficient to cause irreversible damage to plant growth and development
The results of the analysis of variance (ANOVA) analysis showed that there was no significant effect of prior heat stress on the shoot height of the C. papaya (p
There was no significant difference of prior heat on the leaf area (p>0.05).The fresh weight and dry weight of plants under different heat treatments are shown in Fig. 3 and 4 respectively
Summary
Heat stress is often defined as the rise in temperature beyond a threshold level for a period of time sufficient to cause irreversible damage to plant growth and development. It is a complex function of intensity (temperature in degrees), duration and rate of increase in temperature. Concern about temperature increases on a global level has sparked research in quantifying plant responses to heat stress This has become of particular interest to a wide range of scientists and disciplines as evidence suggests that increased temperatures such as that associated with global warming will have widespread adverse effects on species diversity (Davis et al, 1998), food-web and ecosystem structuring (Cao and Woodward, 1998), dominant vegetation (Harte and Shaw, 1995), plant physiology and development (Sato et al, 2000) climate (McCarty, 2001), and phenology (Menzel and Fabian, 1999). The objectives of this research work are to determine the effects of prior heat stress on some growth parameters of C. papaya and to study the response of photosynthetic pigments of the plants to prior heat stress
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