EFFECT OF POTASSIUM NITRATE AND ADENOSINE TRIPHOSPHATE ON PRE- AND POST-HARVEST GERBERA (GERBERA JAMESONII L.) PLANTS

The pot experiment was conducted during the two consecutive seasons of 2016 and 2017 in plastic house at Horticulture Research Station, Mansoura, Dakahlia Governorate, Egypt as pre-harvest treatments. The main objective of the first experiment was to study the effect of two rates of adenosine triphosphate(0.0 and 7.0 g/l) alone or combined with potassium nitrate at the dose of 2.5, 5.0, 7.5 and 10.0 g/pot, on vegetative growth, flowering and chemical constituents of gerbera (Gerbera jamesonii). The highest values of plant height, number of leaves per plant, leaf area, number of flowers per plant, flower diameter, stalk length as well as the contents of total chlorophyll, carbohydrates, N, P, and K in plants were achieved with adenosine triphosphate(ATP) at 7 g/l as weekly foliar spray with significant difference compared to control. Also, increasing potassium nitrate from 2.5 up to 10.0 g/pot gradually increased the above mentioned parameters during both seasons. Furthermore, using the highest doses of potassium (7.5 and 10.0 g/pot) in interaction with ATP at 7 g/l significantly increased gerbera growth, flowering and chemical constituents compared to untreated plants and the other interaction treatments. From the first experiment the best interaction treatments were 7.5 and 10.0 g potassium nitrate/pot plus1 7 g ATP/l, these treatments were in the second experiment to study the effect of different pulsing solutions on flower vase life, solution uptake and flower fresh weight of gerbera. The obtained results revealed that, the longest vase life of gerbera and the highest quality cut flowers were obtained by using the combination treatments between (7.5 g potassium nitrate/pot + 7 g ATP/l) combined with 3% sucrose + 8-HQS at 200 ppm as holding solution. By studying simple correlation coefficients, gerbera cut flowers vase life exhibited strong positive relationship with each of water uptake and flower fresh weight which, indicated that the increase in these parameters was accompanied by increasing vase life of gerbera cut flowers under the effect of interaction treatments of pre and postharvest.