Spatiotemporal Pattern of Potassium Deficiency Symptoms and K + Concentration in Cotton Leaf

Abstract

In order to explore the physiological mechanism of an unusual phenomenon that potassium (K) deficiency symptom first occurs in medium and upper leaves rather than lower leaves of cotton plants, field experiments were conducted at Shangzhuang Experimental Station of China Agricultural University with a low K soil (64.0 to 70.9 mg kg of available K) in Beijing (40o08′N, 116o10′E) during 2013 and 2014 growing season, using CCRI 41 (Gossypium hirsutum L.; susceptible to K deficiency) as material. There were three potassium treatments: control (no potassium applied), low potassium (225 kg K2O hm) and high potassium (375 kg K2O hm). We observed potassium deficiency symptoms of the main stem leaves from squaring stage to late stage of flowering and boll period and determined the content of K + of blade. It was found that K deficiency symptoms developed upward from the leaf located at the tenth node or so of mainstem, and those leaves below this node did not show symptoms during the whole season. However, this type of upward development of K deficiency symptoms was not successive; some leaves at medium part of mainstem (the 16th node or so) were always normal or near normal. There was no necessary link between the pattern of K deficiency symptoms and K concentration in cotton leaves. The latter generally increased with the leaf position raised from bottom to top, which is in accord with the common pattern under K deficiency. However, the increased magnitude from bottom to top and the leaf position with a larger increase in K concentration were different at contrasting growth stages, as well as between 2013 and 2014. The K concentration in most leaves decreased faster or slower over time. Nevertheless, some young or functional leaves (e.g. from the 7th to 14th node in 2013, and from the 13th to 16th node in 2014) showed an in第 12期 陈 乔等: 田间条件下棉花叶片缺钾症状及钾含量的时空动态研究 1889 crease of K concentration during the period from squaring stage to peak blooming stage. In conclusion, the spatiotemporal pattern of K deficiency symptoms in cotton leaves is more complicated than expected; and according to K concentration in leaves we cannot explain it well. The further study should focus on the susceptibility to K deficiency in leaves at different positions, and K redistribution in whole plant.