| Calcium(Ca), as an essential nutrient element for the growth of pineapple, is an important component of cell wall and membrane system. The level of Ca content of peduncle is closely related to the stability of the membrane system, the mechanical strength of the cell wall and the soundness of the cell structure with the result that impacts physiological diseases of peduncle.The study, was carried out by field investigation, analyses the main occurred time of peduncle cracking and influence factors on 'TN17' pineapple; furthermore, to analyze effects of Ca on peduncle cracking and its efficiency,the characteristic of pineapple on the absorption of Ca accumulation was combined with fertilizer external Ca; at the same time, the differences of Ca concentration in D-leaf and peduncle, and enzyme activities in peduncle were analyzed between the relation of Ca and peduncle cracking and its physiological mechanism under different Ca treatments. Its aimed to provide technical support and basic theoretical basis for the high yield, the high efficiency cultivation and the mechanism of deep exploration on peduncle cracking of'TN17'pineapple.The results of investigation and analysis indicated that the phenomenon of peduncle cracking on 'TN17' pineapple mainly occured in peduncle smoking period(SPP) to harvest period,and the easily happening time slot was SPP to the period of small fruiting. The characteristic of pineapple variety, active accumulated temperature of pineapple growth period, P, K, Ca nutrition and the content of zeatin(ZT) and gibberellin(GA3) on peduncle were the four important factors influencing peduncle cracking of 'TN17'Tpineapple. Among them, the peduncle cracking rate(PCR) was negatively correlated with the active accumulated temperature. Being increased application of K and Ca fertilizers can significantly reduce the pineapple PCR, and the efficiency of fertilizer Ca is significantly better than that of fertilizer K. The content of protopectin(PP) and ZT and GA3, catalase (CAT) activity on peduncle were reduced,and the activity of cellulose(CX), polygalacturonase(PG) and polyphenol oxidase(PPO) were increased, these were the main physiological causes for 'TN17' pineapple peduncle cracking.Under the condition of the conventional fertilization in Hainan, the apparent recovery efficiency of applied nutrient (RE) of N, P, K, Ca and Mg were 16.28%,11.66%, 35.76%, 36.49% and 25.37% on 'TN17', respectively. The average of RE of the total fertilizer was 26.02%. To compared with free control fertilization treatment(FFT), fertilization could significantly increase the yield of pineapple and increased by 45.47%. The accumulation of N, P, K, Ca and Mg were 232.07 kg·hm-2, 47.56 kg·hm-2, 512.54 kg·hm-2, 207.95 kg·hm-2 and 20.36 kg·hm-2 in 'TN17'pineapple,respectively. The requirement for Ca was third after K and N, and the accumulation of Ca was only 10.39% lower than that of large element N. On the nutrient absorption,Ca nutrient requirement for 1000 kg fruit (NRFca) of 'TN17' was 5.25 kg,which significantly higher than the NRFca of S C and MD-2. There was good economic benefit of 'TN17', and the ratio of output to input was 2.97:1, and the net income increased by 54.82%, higher than traditional pineapple variety, and there has been an ever-growing market demand.Field experiment results showed that applying Ca fertilizer could significantly increase yield of 'TN17', and the content of Ca in D-leaf and peduncle were directly increased significantly, and that the correlation between the PCR and Ca content in D-leaf and peduncle were highly significant negative. The mechanism of action of Ca can significantly reduce the PCR might look as follows: High concentration of Ca in peduncle after fertilizer external Ca source resulted in increase of PP increased significantly, and that increased pineapple peduncle strength and resistance to stress;the activities of CAT and superoxide dismutase(SOD) which both belong to radical scavenging enzyme system were increased significantly; meanwhile, the activities of PPO, CX and PG in cell-wall metabolism were decreased, and both processes of cellular senescence and cell-wall hydrolysis under adversity were got effective regulate and control, thereby the mechanical strength of the peduncle was increased,and the PCR was reduced. Moreover, there was a significant negative correlation between the PCR and the content of PP and CAT activity on peduncle respectively,and a significant positive correlation between the PCR and PPO activities.Overall, these results indicated that reduction of PCR by Ca application was obtained through increasing pectin content and activities of SOD and CAT,but reducing activities of PPO, CX and PG, and thus to maintain mechanical strength of peduncle. Ca application could be an important measure to reduce PCR in 'TN17',with optimum application rate being 300 kg·hm-2, and optimal application time from fast growth period ? to 10 days after flower forcing. |
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