| In the study, three cultivars namely ‘Xingyu-2’, ‘PLRF’ and ‘Xingyu-1’, were used as test materials by pot experiment, by using DTR300 and weighing method to control soil water content and timely pay, pending the soil relative water content were 75±5%. The materials were randomly divided into two groups, one of normal water supply(CK), another group of persistent drought stress(D) and rehydrated 7d. The yield and starch quality at maturity, and the growth characteristics,photosynthetic characteristics, chlorophyll fluorescence parameters, mineral nutrition, glucose metabolism and activity of enzyme at the sub-taro forming stage were analyzed, in order to interpret the effect of drought stress on canna rhizome yield and starch quality from the physical point of view and to provide a theoretical basis for revealing physiological mechanisms of drought-resistant,water saving and good quality cultivation of canna, the results obtained are as follows:1. The yield of canna rhizome was significantly reduced and the quality of starch was affected under drought, the impact of drought on the yield was greater than the quality and on the accumulation of N, P, K was greater than on the content for rhizome. Meanwhile, the effect of drought on the accumulation of P was lsee than N and K, Drought significantly reduced the accumulation of N, P, K, amd the content of N was affected little, but the content of P increased,while the content of K and soluble sugar for three varieties significantly reduced, there were differences between the content of soluble protein and fat in the different varieties rhizome under drought. The starch granules in the rhizome reduced significantly, the proportion of small particles rose, and the swelling power with the temperature required for maximum swelling was affected also.The impact of drought on the ‘Xingyu-1’ was larger than the other two varieties.2. The content of starch for ‘Xingyu-2’ and ‘PLRF’ had affected little, but the total starch,amylose and amylopectin content of ‘Xingyu-1’ was significantly reduced under drought, and the phase transition temperature and enthalpy of gelatinization in different stage of rhizome has been significantly changed. The total ΔH for ‘Xingyu-1’ obviously reduced, and the energy of starch gelatinization required distinctly reduced under drought.3. The plant height, stem diameter, leaf area and rhizome volume of canna were inhibited under sustained drought stress at the sub-taro forming stage, But the degree of inhibition was different due to varieties of drought resistance, the degree of inhibition expressed as: ‘Xingyu2’<‘PLRF’ < ‘Xingyu-1’. The growth of morphological index for the three cultivars has been increased, but was still significantly lower than the control after rehydration 7d.4. The content of Chl.a, Chl.b, Car, total chlorophyll, and the Pn, Gs, Tr, Ls were significantly decreased, Ci was significant increased under continuous drought. Rehydration 7d, the content of photosynthetic pigment and Pn, Gs, Ci, Tr for the three cultivars was still distinctly lower than the control, but the photosynthetic pigment content of the other two varieties returned to the control,and the effect of drought on the photosynthetic pigment and photosynthetic for ‘Xingyu-1’ was greater than the other.5. The reaction centers of PSII for the three cultivars has been suffered photoinhibition. the Fo,q N was increased and the Fm, Fv/Fm, Fv/Fo, q P, ΦPSII, ETR reduced under drought. Rhydration7 d, the Fm, Fv/Fm, Fv/Fo, q P, ΦPSII and ETR were still significantly lower, while q N was higher than the control, showed that the reaction center of PSII and photosynthetic system has been suffered irreparably damaged, and the the effect of drought on the fluorescence parameters for‘Xingyu-1’ was larger than the other.6. The accumulation and content of N, P, K in different organs significantly reduced, and the effect of drought on N, K was greater than P. Rehydration 7d, the accumulation of N, P, K and the N,K content was still obviously lower than the control, while the P content was significantly higher,the impact of drought on ‘Xingyu-2’ was smaller than the other two varieties. Rehydration was more conducive to the P uptake than N and K.7. The content of glucose and fructose increased clearly among different organs, especially in the leaves, the rose expressed as: ‘Xingyu-2’ >‘PLRF’ > ‘Xingyu-1’. Drought made the content of starch distinctly decreased, while the sucrose content showed a significant increase after a significant reduction. The effect of drought on the starch was less than other organs, and effect on sucrose was greater in the rhizome. Rehydration 7d, the content of glucose and fructose in different organs decreased, the sucrose content in roots, stems, leaves and starch returned to the control,despite the rose of sugar and starch in the rhizome, but was still significantly lower.8. Drought stress made SS, SPS in leaves and AGPase, SSS, SBE, DBE in rhizome tend to increase first, and then decrease. With prolonged drought stress, the activity of SS, SPS, AGPase,SSS, SBE was lower than the control, but the activity of DBE for the three varieties and the activity of AGPase, SSS for ‘Xingyu-2’ was higher. Rehydration 7d,the activities of SS, SPS for the three cultivars and DBE for ‘Xingyu-1’ were not recovered to the control, but the enzyme activity involved in rhizome starch synthesis for ‘Xingyu-2’ and ‘PLRF’ were increased to the control. The impact of drought on the activity of enzyme for ‘Xingyu-1’ was more than ‘PLRF’ and ‘Xingyu-2’. |
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