EFFECTS OF SUBSTRATE MOISTURE CONTENT ON GROWTH AND PHYSIOLOGICAL RESPONSE OF CHILI PEPPER (Capsicum annuum L.)

Crops in semiarid ecosystems have to deal with adverse environmental factors such as water shortage. Therefore, the objective of this experiment was to evaluate growth and physiological responses of three chili pepper cultivars (Capsicum annum 'CM-334', 'Jalapefio M', and 'NuMex Heritage 6-4') under controlled drought conditions in a greenhouse. We speculated that 'CM-334', a selection from wild population, would be more tolerant to drought condition than `Jalapefio M' and 'NuMex Heritage 6-4'. The plants were irrigated at one of the four substrates volumetric water content (VWC) set points: 0.15 L.L-1(15 %), 0.25 L.L-1(25 %), 0.35 L.L-1 (35 %), and 0.45 L.L-1 (45 %) using a sensor based automated irrigation system. The experimental design was randomized complete block with three chili pepper cultivars, four VWC levels, two blocks (replicate), and four plants in each block. Two-way analysis of variance were used for data analysis, and Tukey's honest significant difference (HSD) was applied (p <= 0.05). As VWC decreased from 45 to 15 %, height, stem diameter, fruit fresh weight (wt.), leaf, stem, root and total dry wt of all three cultivars decreased, but the reductions varied according to cultivar. Growth reduction was smallest in 'NuMex Heritage 6-4', followed by 'CM-334' and 'Jalapefio M' when compared VWC of 45 with 15 %. As VWC decreased, leaf net photosynthesis (Pn), transpiration (E), and stomatal conductance (gs) of 'CM-334' and 'Jalapefio M' decreased; however, those of 'NuMex Heritage 6-4' did not change. In addition, VWC did not impact the chlorophyll fluorescence (Fv/Fm), regardless of cultivar. Based on the growth and physiological responses to four VWCs, we conclude that 'NuMex Heritage 6-4' was more drought tolerant and 'Jalapeno M' was least tolerant among the three cultivars.