不同海拔下玉米生物学干重的动态变化研究

以紧凑型玉米郑单958、半紧凑型玉米东单60和平展型玉米长玉13为试验材料,分别在重庆海拔220、530、1 300 m地区种植,测定玉米叶片、茎秆、叶鞘以及果穗干重的动态积累,研究不同株型玉米在不同海拔高度地区生物学干重的形成规律,并结合产量进行差异分析。结果表明,3种株型玉米的叶片干重均表现为高海拔地区持续上升至峰值,而在中海拔和低海拔地区均先上升后下降,各时期变化总趋势为中海拔地区>低海拔地区>高海拔地区;玉米茎秆和叶鞘干重的动态变化趋势基本一致,郑单958干重受海拔的影响较小,东单60干重达最大值的时期各不相同,长玉13在散粉期或灌浆期达最大值;果穗干重随生育时期推移呈直线上升至最大值,且随海拔高度的升高而增加;子粒产量随海拔升高而增加,但平展型玉米以中海拔地区最高。因此,应重视玉米育种和生产上海拔高度对玉米生物学干重的调控作用。     

Do strain differences in microalgae alter their relative quality as a food for the rotifer Brachionus plicatilis?

Brachionus plicatilis is used in aquaculture to feed larval fish and crustaceans. It is well established that different prey species alter rotifer productivity. Isochrysis galbana is one microalgal prey that is commonly fed to rotifers, and there are several strains of this flagellate available to aquaculturists. As microalgae strains may differ in their composition and growth attributes, we rigorously examined if growth and biochemical differences in I. galbana strains elicit differences in the growth and biochemical attributes of B. plicatilis. Four I. galbana strains and one strain of the flagellate Nanochloropsis were grown under standard conditions. Growth rate, cell volume, production, and composition (dry weight, carbohydrate, protein, lipid) were measured. Significant differences occurred between strains in all of these attributes (at times 2 to 3 fold), but no clear pattern emerged that one strain was superior. Of note was that for some measurements, strain differences were significantly greater than differences between species. The strains were then fed to rotifers, and a number of parameters were measured: growth rate, reproductive rate, fecundity attributes, a number of developmental rates, and composition (dry weight, carbohydrate, protein, lipid). There were significant effects of prey strain on some of these attributes, but none was dramatic (rarely more than 10% and occasionally up to 30%), suggesting that aquaculturists need not be too concerned regarding which I. galbana strain they use. However, we do indicate subtle differences, induced by different prey strains and suggest that for maximum productivity these differences should be considered.