Growth, development and nutritional value of Amaranthus tricolor L. as affected by salinity and harvesting procedure

[摘要] ENGLISH ABSTRACT:Low crop productivity in arid and semi-arid regions is aproblem caused by water stress as well as associated high levelsof soil and water salinity. An increased demand for salttolerant crops is experienced in these regions. Amaranth is aglycophyte and C4 dicotyledonous crop, well adapted to arid andsemi-arid regions. Previous studies on the physiologicalresponse of salt-stressed amaranths have indicated that thiscrop is salt tolerant. As vegetable, amaranths can be harvestedby uprooting and by topping. The most common harvesting methodis by topping, allowing repeated harvesting. When harvested bytopping, the cutting height is an important parameter that maybe manipulated to optimise growth rates. In this study, plantswere exposed to different salt stress levels and harvestingprocedures while yield and quality of Amaranthus tricolor wereinvestigated. Nutrient solutions at four different electricalconducti vi ty (EC) levels were used to fertigate the plants. Athigh EC levels (4 mS cm-l and 8 mS cm-lj, the length and diameterof main stems, internode lengths, stem weights as well as rootweights were reduced, especially with a longer growth period.However, the shoot: root ratio and leaf protein yields increasedand flowering was delayed. The best leaf yield was obtainedwhere plants were fertigated at an EC of 4 mS cm-l for 45 days.The cutting height did not affect leaf yield, growth rates andleaf protein yield in plants fertigated at EC levels of 1, 2 and4 mS cm-l. At an EC of 8 mS cm-l, the growth rate recovered to avalue similar to that of plants fertigated with an EC of 2 mS cmonlywhere plants were topped at 25%. With this lessdestructive cutting height (topped at 25%), leaf yields, growthrates and ·leaf calcium and protein yields at an EC of 8 mS cmwere superior to that of plants topped at 50%. In plants toppedat 25%, the recovered growth rates at EC 8 mS cm-l was probablydue to more photosynthetic active tissue left after cuttings, resulting in the accumulation of compatible solutes for osmoticadjustment.

[发布机构] Stellenbosch University