| dc.description.abstract | Environmental stresses, such as water stress have a major impact on plant growth and survivaL Lack of water causes reductions in growth rate and physiological processes affecting bioproductivity, which in turn lower agricultural production thereby contributing to food insecurity. This research was designed to investigate the effects of soil water deficit on growth and physiology of two African nightshades, which are widely consumed due to their high nutritional value. The aim of the study was to determine the effects of water deficit on their growth, chlorophyll fluorescence and gas exchange parameters, and on their chlorophyll and nitrogen content. The experiment was carried out at Maseno University, Botanic Garden glasshouse at Maseno University. The experiment was laid out as a completely randomized design (CRD) two factorial, consisting of four treatments and three replications. The treatments were: Tl-watering daily (control), T2-watering after every three days (the 3rd and 6thday), T3-watering the 9thday and T4-watering the 12thday. African nightshades (S. scabrum Mill. and S. villosum Mill. subsp. miniatum, seeds were grown in 20 litre plastic pots in loam moist soils having a pH of around 4.6 to 5.4. Growth parameters measured included; plant height and the stem diameter using a meter rule and a veneer caliper respectively, and by counting the number of leaves. The root to shoot ratio was determined at the end of the experiment. Stomatal conductance and leaf temperature were determined by use of a steady-state porometer. Chlorophyll fluorescence was determined by use of a portable fluorescence monitoring system. Soil moisture content was determined gravimetrically. Chlorophyll content was determined through extraction and absorbance of chlorophyll solution read spectrophotometrically. Foliar chlorophyll content was determined using a chlorophyll meter. Statistical analysis involved analysis of variance (ANOVA) using MSTAT-C statistical computer package to determine the differences between the two species and the four treatments on the parameters using the Least Significant Difference test at 5% level. Results showed that the two species of African nightshades were significantly (p~0.05) affected by water deficit. Growth parameters slightly increased with increase in water deficit and reduced significantly (p~0.05) with further increase in water deficit. Water deficit caused a decrease in stomatal conductance and an increase in leaf temperature. The root to shoot ratio increased with increase in water deficit. Foliar chlorophyll content decreased with increasing water deficit among the treatments but also increased throughout the experimental period in all the treatments. Chlorophylls a, b and total chlorophyll also showed a general decrease with increasing water deficit. From the results obtained, it can be concluded that among the two species S. scabrum Mill. was more tolerant to water deficit and therefore it is recommended to be grown in water deficient regions as compared to S. villosum Mill. The results of this study can be used to recommend better management plant strategies to drought, as it considers effects of water deficit on the growth and physiology of the two African nightshade species. | en_US |
