Applications of xerophytophysiology in plant production – The potato crop improved by partial root zone drying of early season but not whole season

Abstract

Partial root zone drying (PRD) has been used as a technique in the production of many crops. However, the extent or duration of the drying treatment would change the effect and the mechanisms in terms of plant water relations are not clear enough. The aim of this research was to evaluate the PRD effect with shorter or longer drying duration in a potato crop and elucidate the mechanisms based on plant water relations. Potato ( Solanum tuberosum L. cv. May Queen) was grown in experimental plots under plastic rainout shelters. Three treatments: (1) whole-season PRD, (2) early-season PRD for 8 weeks and then return to normal irrigation for the remainder of the season and (3) normal irrigation as control, were arranged in a Latin square design in 9 plots. Water was supplied by drip irrigation to one side of the potato row once every 5 days on average, and the other side of the row was allowed to dry for 15 days, and then the irrigation line was moved to the dry side and the wet side allowed to dry. Pressure–volume curves were used to analyze the osmotic adjustment induced by PRD and a modified mathematic equation, − Ψ − 1 = Ψ FT − 1 − π s + a − 1 [ ζ 0 − β ( 1 − ζ ) − ζ ap ] e − α ( 1 − ζ ) + π s + a − 1 [ ζ 0 − β ( 1 − ζ ) − ζ ap ] was used to compare the pressure–volume relations. As shown by the results, tuber yield and photosynthetic activity were increased by the early-season PRD treatment, but not by the whole-season PRD treatment because the whole-season PRD treatment reduced the leaf area index. By analyzing the pressure–volume curves, it was found that osmotic adjustment occurred and the turgor potential was higher in potato leaves in the PRD treatments. The fraction of water in the cell symplasm was higher and that in apoplasm was smaller in PRD-treated potato leaves. Both the osmotic potential and relative water content at the point of incipient plasmolysis were lower in potato leaves in the PRD treatments, suggesting that the plants in the PRD plots were more resistant to water stress, which was also confirmed by the analysis of transpiration declining curve of excised leaves. In conclusion, the PRD treatment was effective in improving potato tuber yield, but early-season treatment rather than the whole-season treatment should be adopted.