Studies On Differences Of Potassium Nutrition Efficiency Between Banana Genotypes

Potassium is one of the key nutrition elements of plant growth. With the yield and quality of agricultural products rising, crop needs more K+ to meet its requirement. However, most potassium (98%) in soil is a mineral state and slowly available form. So most Potassium in soil can not be used directly by plant and often have difficult to meet the needs of crop growth. The banana is a typical hi potassium crops, in some areas the low K had affected the growth and quality seriously. So it has important theoretical and practical significance to explore plants own potential for improving soil K and fertilizer K use efficiency by biological method.This study used 13 different types of banana varieties, carried out preliminary screening on tested materials by sand culture experiment and then water culture, discussed the mechanism of different types of banana varieties adapt to low potassium soil, studied banana growth status, nutritional status and root morphological and physiological characteristics, revealed the mechanism of potassium nutrition efficiency difference of different banana varieties, provided a theoretical basis to select appropriate banana varieties and achieve high yield based on soil nutrition status. Main finding as follows:1. Under normal conditions, the 13 materials had been carried out sand culture experiment. And then four better nutrition absorption varieties were initially selected by three indicators-plant height and shoot weight and chlorophyll. They were namely'Pisang ceylan','Brazil banana','bengalese fen jiao banana','Sanya fenjiao banana'.2. The biomass, potassium content, and potassium accumulation, absorption and utilization of the four banana varieties had been researched with low potassium (-K) and normal potassium (CK) conditions by solution culture. The results showed that, banana biomass, K+ use efficiency and potassium accumulation of aboveground plant at different growth stage all had significant differences between varieties on two potassium levels The four varieties were classified as: 'Pisang ceylan'and'Brazil banana'were belonged to high efficient potassium accumulation and low inefficient use variety, while'Bengalese fen jiao banana','Sanya fenjiao banana'were belonged to low efficient potassium accumulation and high inefficient use variety. And we also found that low potassium stress could reduced biomass and aboveground K accumulation of banana significantly, but improve K utilization efficiency significantly.Therefore, screening and cultivate high K use efficiency and early growth with strong potassium accumulation characteristics of banana varieties is a effective way of relieving serious potassium shortage in the South soil.3. By solution culture with low potassium (-K)the study showed that the banana root weight and root volume were significantly reduced than under the normal potassium (CK) condition, but the decreasing range of was less than K inefficient cultivar. But root active absorption area, total surface area, root H+ secretion and the root activity of K efficient cultivars were bigger than of K inefficient cultivars. Km values of potassium uptake, Cmin, and a value of K inefficient cultivars were all less than of K inefficient cultivar, but Imax values were generally larger than the K inefficient cultivar. So this indicated the adaptability of bananas on the low potassium stress had relation with the K+ affinity for root, the critical K+concentration in growth medium and the maximum absorption rate.4. With low potassium (-K) and normal potassium (CK) conditions by solution culture, the study investigated the antioxidant enzyme activities of K efficient cultivars are'Pisang ceylan' and'Brazil banana'. And K inefficient varieties are'Bengalese fen jiao banana','Sanya fenjiao banana'.The results showed that'Pisang ceylan'and'Brazil banana'were carried out by increasing root cell membrane permeability, malondialdehyde (MDA) content and increasing soluble protein significantly, Pro, SOD activity could achieve a protective response to the use of potassium.'Bengalese fen jiao banana','Sanya fenjiao banana'all also increased than in normal potassium treatments, but the soluble protein, Pro, SOD activity increased less than'Pisang ceylan'and'Brazil banana', while the membrane permeability and MDA increased significantly more than'Pisang ceylan'and'Brazil banana'. This indicate'Pisang ceylan'and'Brazil banana' had a strong self-protection capability on low K stress, while'bengalese fen jiao banana'and 'Sanya fenjiao banana'were less capable of such self-protection, which resulted in increasing cell membrane damage. So the solubleprotein, Pro, SOD and other antioxidant enzyme activities could be used as one evaluation index for tolerance to low potassium stress e difference in banana varieties.