Correlation of Leaf and Root Senescence During Ripening in Dry Seeded and Transplanted Rice

Dry seeding is a resource-saving rice establishment method. With an equivalent yield, dry seeded flooded rice （DSR） has been considered as a replacement for traditional transplanted flooded rice （TFR）. However, the differences in leaf and root senescence during grain filling between DSR and TFR were seldom identified. In this study, the root length, root tip number and leaf senescence of rice varieties Huanghuazhan and Yangliangyou 6 during ripening were compared between DSR and TFR. Results showed that top three leaves in DSR had the characteristics of relatively lower SPAD value, lower N content and premature leaf senescence. In addition, both the total root length and total root tip number of DSR were significantly lower than those of TFR. In conclusion, premature and quick leaf senescence was related with inadequate root length and root tip number during ripening, which might result from the deficiency of nitrogen supply in DSR. Techniques on improving leaf nitrogen status and delaying the leaf senescence during grain-filling in DSR should be developed in future researches.

Effects of Different Potassium (K) Fertilizer Rates on Yield Formation and Lodging of Rice

As one of the most important nutrients for plants,potassium(K)has substantial effects on growth and development of crops.Present study was conducted in three different sites in South China in late season in 2019 with the objective to study the effects of different applied amounts of K fertilizer on yield formation and lodging of rice.Four K fertilizer treatments,K_(0):0 kg potassium oxide(K_(2)O)ha^(−1)(control);K_(1):64.20 kg K_(2)O ha^(−1);K_(2):128.55 kg K_(2)O ha^(−1) and K_(3)153.90 kg K_(2)O ha^(−1) were applied in the field experiment.The results showed that K_(2) and K_(3) treatments significantly increased panicle number per unit area,grain number per panicle,seed-setting rate and the grain yield of rice compared with K_(0) treatment.Higher net photosynthetic rates were recorded in K_(2) and K_(3) treatments than K_(0) treatment at tillering stage,heading stage and maturity stage.K fertilizer treatments also increased the chlorophyll content and dry matter accumulation by 6.16–23.52%and 21.32–64.59%compared with K_(0) treatment,respectively.Moreover,the total N and K accumulation in the aboveground tissues of rice significantly increased under K_(2) and K_(3) treatments compared with K_(0) treatment.Furthermore,compared with K_(0) treatment,K fertilizer treatments significantly enhanced the breaking-resistant strength by 40.94–144.24%and reduced the lodging index of rice by 13.14–36.72%.

Effects of Intelligent Irrigation on Photosynthetic Characteristics of Citrus Leaves and Fruit Quality

[Objectives]This study was conducted to improve the water use efficiency and fruit quality of citrus,and realize the automatic irrigation and standardized production in citrus orchards.[Methods]With Orah as the research object,the effects of intelligent irrigation management in citrus orchards on citrus leaf chlorophyll content,photosynthetic characteristics and fruit quality were investigated by comparing with conventional farmer management.[Results]The smart irrigation measure in citrus orchards significantly increased the SPAD value of leaves at the maturation stage of citrus,and simultaneously significantly improved the photosynthetic rate,transpiration rate and stomatal conductance at the flower bud differentiation stage,as well as the photosynthetic rate,transpiration rate,stomatal conductance and intercellular CO_(2) concentration at the maturation stage.However,the effects on the photosynthetic characteristic indexes in the rainy season were not significant.Compared with conventional experience management,the smart irrigation management measure of citrus orchards increased the edible rate and juice rate of citrus by 4.53 and 3.69 percentage points,respectively,and increased soluble solids,total sugar,vitamin C and sugar-acid ratio by 16.75%,20.86%,24.10%and 13.17%,respectively.[Conclusions]The smart irrigation management fully met the water demand for citrus growth due to timely irrigation,significantly improved the photosynthesis indicators of citrus leaves during drought,and significantly improved the quality of citrus.