Wheat Seed Presoaking for Improved Germination

Seed presoaking improves wheat germination under marginal moisture conditions. The duration of seed presoaking was studied at The University of Arid Agriculture, Rawalpindi, using 10 wheat varieties. Seed presoaking beyond 12 h does not improve germination further, and beyond 21 h, germination rate is drastically reduced.     

Osmotic Adjustment in Maize (Zea mays L.): Changes with Ontogeny and its Relationship with Phenotypic Stability

Genetic variation for osmotic adjustment was examined in a group of maize hybrids during vegetative and silking stages. Estimates of osmotic adjustment were derived from measurements of leaf relative water content (RWC) and osmotic potential (Ψ o ) before day-break. The degree of adjustment was estimated from the In RWC/In Ψ o relationship. All cultivars examined showed some degree of osmotic adjustment and significant differences (P < 0.05) were found among them. The utility of measurements in early vegetative stages as a mean of selection for osmotic adjustment in silking stage was established. A positive tendency was observed between osmotic adjustment and phenotypic stability.     

Interactive Effects of Salinity and Biological Nitrogen Fixation on Chickpea (Cicer arietinum L.) Growth

The effect of salinity on the nodulation, N-fixation and plant growth of selected chickpea- Rhizobium symbionts was studied- Eighteen chickpea rhizobial strains were evaluated for their growth in a broth culture at salinity levels of 0 to 20 dS m⁻¹ of NaCl + Na₂SO₄. Variability in response was high. Salinity generally reduced the lag phase and/or slowed the log phase of multiplication of Rhizobium. Nine chickpea genotypes were also evaluated for salt tolerance during germination and early seedling growth in Petri dishes at five salinity levels (0–32 dS m⁻¹). Chickpea genotypes ILC-205 and ILC-1919 were the most salt-tolerant genotypes. The selected rhizobial strains and chickpea cultivars were combined in a pot experiment aimed at investigating the interactive effect of salinity (3, 6 and 9 dS m⁻¹) and N source (symbiosis vs. inorganic N) on plant growth. Symbiotic plants were more sensitive to salinity than plants fed mineral N. Significant reductions in nodule dry weight (59.8 %) and N fixation (63.5 %) were evident even at the lowest salinity level of 3 dS m-¹. Although nodules were observed in inoculated plants grown at 6 dS m-¹, N-fixation was completely inhibited. The findings indicate that symbiosis is more salt-sensitive than both Rhizobium and the host plant, probably due to a breakdown in one of the processes involved in symbiotic-N fixation. Improvement of salinity tolerance in field grown chickpea may be achieved by application of sufficient amounts of mineral nitrogen.     

兰旗榆——一个在干旱草原区很有发展潜力的造林树种

兰旗榆为白榆的一个地理生态变种,在锡盟浑善达克沙地及其南缘的镶黄旗、正镶白旗、正兰旗等地区生长表现突出。该树种较之其它的白榆品种具有抗旱、抗寒、抗风沙,物候期早,所需积温低以及生长迅速等优良特性,对我区北部干旱草原气候生态条件适应能力强,在草原造林中有着其它树种不可替代的地位和作用,建议大力推广。     

郁金香花芽分化的解剖学研究

利用石蜡切片法研究了郁金香花芽分化的进程及温度变化对花芽分化的影响。结果表明：郁金香鳞茎内顶端生长点的分化过程可以分为营养生长期，生殖茎端形成期，花器官分化期，花器官伸长期４个时期花芽分化从７月上旬开始，８肿旬结束。在贮藏期间，郁金香鳞茎内顶端生长点前期发育速度较慢，后期发育速度较快，并按由外向内的顺序进行。     

野蚕越冬卵的孵化和年发生代数的研究

研究证实(1980—1984年),嘉湖平原野蚕年发生三代.越冬卵始孵期为四月中旬,盛期为六月中旬.但近半个世纪以来.很多人一直误认为四月中旬发生的野蚕是第一代,六月下旬发生的为“第二代”,事实上都是越冬卵孵化的幼虫.均为第一代.经测定,四月下旬越冬卵孵化率为0.15%,5月下旬为7.9%,6日20日为91%.本区野蚕产越冬卵最的早在9月17日,高峰期在11月上旬.结束期在12月14日,越冬卵产出越早,翌年卵孵期也早,孵化的早和迟之间可相差122天.野蚕越冬卵翌年孵化期长的原因.与秋冬产卵期长及桑园生态环境复杂有关.据室内4月24日越冬卵孵化的幼虫连续饲养,到第三代卵期恰与室外第二代卵期相重叠,说明自然界发生第四代是可能的,但真正存活率在1%以下.在防治措施上,以在越冬卵孵化高峰期(6月15—20日)施用0.1%敌敌畏.防效最好.     

无芒雀麦人工草地初级生产力动态的研究

以无芒雀麦人工草地为研究对象，对其生物量的季节及垂动态进行连续４ａ的研究。为促进无芒雀麦草地在河南省的高产丰收提供基础资料及其理论依据。     

杏大小孢子与雌雄配子体发育

以龙垦２号品种为试材、分期取样固定，按常规石蜡法制片观察。结果表明，哈尔滨地区３月５日花药壁已分化，次生造孢细胞和花粉母细胞已形成。四分体属同时型，其排列方式为四面体型，成熟花粉呈椭圆形、具３孔沟。有的药室内产生巨型细胞。子房内具２胚珠，１枚后期退化消失。胚珠倒生，近珠孔处为双被，其余部分愈合；厚珠心，具珠心帽结构；胚囊发育属蓼型。杏雌蕊发育的异常情况较其它果树的比率都大。