NaCl胁迫对续随子离子吸收及荧光特性的影响

以续随子为材料采用温室盆栽法,研究了NaCl胁迫处理对其生长发育、离子分布和叶绿素荧光特性的影响。结果表明：(1) 25mmol•L-1 NaCl胁迫时续随子幼苗的鲜重、干重和株高比对照略有下降,但不显著;随着NaCl浓度的继续增加,三指标均显著降低。(2)盐胁迫影响植物组织的离子分布,Na +浓度增加时,K+、Ca2+和Mg2+浓度均持续下降,K+/ Na+、Ca2+/ Na+、Mg2+/ Na+ 也急剧下降。(3) NaCl胁迫下,续随子幼苗叶片的初始荧光(Fo)、最大荧光(Fm)、PSⅡ实际光化学效率均降低。但在0～25 mmol•L-1NaCl浓度下,Fo、Fm与对照差异不显著。可见,NaCl胁迫下,续随子产生了光合作用的光抑制伤害。     

续随子辐射效应研究及适宜辐射剂量预测

采用7种不同剂量的60Co γ射线辐照续随子干种子，观测射线辐射对M1种子萌发进程中植物形态及生理指标的影响，并对供试材料的适宜辐射剂量进行预测。发芽势及发芽率的调查结果显示，低剂量辐射对发芽势及发芽率有促进作用，剂量大于450Gy时，逐渐转化为抑制作用；幼苗生长量、活力指数及田间出苗率随辐射剂量加大表现出明显的下降趋势；SOD、CAT、APX活性及MDA含量随辐射剂量的增加表现出先升高后降低的变化趋势。研究结果表明，辐射对续随子M1的抑制效应主要表现在发芽整齐度及幼苗生长量上，对发芽率影响较小；SOD、CAT、APX活性及MDA含量变化均可反应材料的辐射诱变效应；500Gy是供试材料一个敏感剂量点；450～500Gy为辐射育种的适宜诱变剂量范围。     

Effects of soil applications of gibberellic acid on the yield and quality of tubers ofSolanum tuberosum L. cv. Bintje

Summary In two outdoor pot experiments with potato (cv. Bintje) gibberellic acid (GA) was applied to the soil on different dates at 25 (Exp. 1) or 12.5 (Exp. 2) mg/pot. Dry-matter yields were reduced by early treatments in Exp. 1. In both experiments fresh yields were increased by an application about 40 days or later after planting (DAP). GA increased the number of tubers, especially when applied 38 or 40 DAP, treatments which also induced the largest shift in size distribution towards the smaller grades. GA reduced the dry-matter content of the tubers, especially when applied 60 (Exp. 1) or 48 (Exp. 2) DAP. Because the development over time of sensitivity to GA was not similar for all yield and quality variables, GA can be used to alter tuber-size distribution without greatly affecting other quality characteristies or yield.     

A review of the biology and control of selected weed species in the genus Oxalis: O. stricta L., O. latifolia H.B.K. and O. pes-caprae L.

This review considers the distribution, weed problems, biology and control of Oxalis stricta, O. latifolia and O. pes-caprae. The rhizomatous O. stricta is a persistent seed-producing weed which invades horticultural crops in North America. Chemical control is generally most effective in situations where soil-applied residual herbicides can be used; in turfgrass however, foliage-applied herbicides provide suppression only. O. latifolia is widely distributed in a range of annual and perennial crops growing in temperate and tropical locations. This pernicious perennial weed reproduces exclusively by asexual structures, underground bulbs, stolons and tubers. The complexities of the perennating system have rendered ineffective a wide range of herbicide families as a means of restricting the spread of O. latifolia. Similarly, cultural methods of control have not been successful. O. pes-caprae also grows and perennates from bulbs. This weed is essentially a problem in cereal crops in Southern Australia and Mediterranean fruit orchards. Cultural and chemical control difficulties and inadequacies are similar to those in O. latifolia. Future research strategies involving weed physiology, herbicide action and cultural control including biological control are discussed in relation to obtaining improved control methods for the selected Oxalis species.     

Timing and propane dose of broadcast flaming to control weed population influenced yield of sweet maize (Zea mays L. var. rugosa)

Farmers are interested to produce sweet maize under organic production systems and propane flaming could be a potential alternative tool for weed control in organic sweet maize production. Therefore, the objective of this study was to investigate the response of sweet maize to broadcast flaming as influenced by propane dose and crop growth stage. Field experiments were conducted at the Haskell Agricultural Laboratory of the University of Nebraska, Concord, NE in 2008 and 2009 using five propane doses applied at three different growth stages of V2 (2-leaf), V5 (5-leaf) and V7 (7-leaf). The propane doses were 0, 13, 24, 44 and 85 kg ha⁻¹. The response of sweet maize to propane flaming was evaluated in terms of visual crop injury, effects on plant height, yield components (plants m⁻², tillers plant⁻¹, number of ears plant⁻¹, cob length and number of seeds cob⁻¹) and fresh marketable yield. The response of different growth stages of sweet maize to propane doses was described by log-logistic models. Based on most parameters tested, V7 was the most tolerant while V2 was the least tolerant stage for broadcast flaming. The maximum yield reductions with the highest propane dose of 85 kg ha⁻¹ were 22%, 12% and 6% for V2, V5 and V7 stages, respectively. Furthermore, a 5% yield reduction was evident with 23, 25 and 36 kg ha⁻¹ of propane for V2, V5 and V7 growth stages, respectively, suggesting that plants flamed at V7 stage can tolerate higher dose of propane for the same yield reduction compared to the other growth stages. We believe that flaming has a potential to be used effectively in organic sweet maize production if properly used.