SEX DETERMINATION IN DIPLOID-TRIPLOID CROSSES OF SPINACIA OLERACEA

Mahoney , D. L. Jules Janick , and E. C. Stevenson . (Purdue U., Lafayette, Ind.) Sex determination in diploid-triploid crosses of Spinacia oleracea. Amer. Jour. Bot. 46(5): 372–375. 1959.—Segregation for sex in spinach was studied in a series of diploid pistillate × triploid staminate crosses. The genetic data indicated that the functional gametes from staminate triploids were not confined to n and n + 1 types. Cytological analyses of progenies from a number of 2n ♀ × 3n (XYY and XYY) ♂ crosses revealed similar but non-homogeneous types of chromosome segregation. These crosses produced 49.3% diploids, 17.9% trisomies, 0.5% with 14 chromosomes, 1.2% with 16 chromosomes, 11.4% with 17 chromosomes, 18.9% triploids, and 0.8% with 19 chromosomes. The reciprocal crosses produced a higher percentage of aneuploid types including 1.7% with 15 chromosomes. Segregation for sex in each of the various chromosome numbered progeny of diploid-triploid crosses was presented and analyzed.     

FLOWER DEVELOPMENT IN DIOECIOUS SPINACIA OLERACEA (CHENOPODIACEAE)

Spinacia oleracea (Chenopodiaceae) is a potential model system for studies of mechanisms of sex expression and environmental influences on gender in dioecious species. Development of the male and female flowers and inflorescences of spinach were studied to determine when the two sex types can be distinguished. We found that female inflorescence apices are significantly larger than those of the male. Flower primordia are similar in size prior to perianth initiation, but the male primordia develop at a faster rate. Another distinguishing feature at this early stage is the larger bract subtending the female primordium. The two flower types become readily distinguishable when the perianth initiates. Male flowers produce four sepals and four stamens in a spiral pattern in close succession. Female flowers produce two alternate perianth parts that enlarge somewhat before the gynoecium becomes visible. There are no traces of gynoecia in male flowers or of stamens in female flowers. We propose that plant sex type is determined before inflorescence development, prior to or at evocation.     

SECONDARY SEX CHARACTERISTICS IN SPINACIA OLERACEA L.: QUANTITATIVE EVIDENCE FOR THE EXISTENCE OF AT LEAST THREE SEXUAL MORPHS

Spinacia oleracea L. was grown hydroponically across an experimental salinity gradient with treatments of 0.0, 1.5, 3.0, 4.5, and 6.0 grams of NaCl/liter of nutrient medium. Plant height, root biomass, vegetative biomass, fruit morphology, average fruit weight, and fruit mass: volume ratio were examined in each treatment to determine if differences other than primary sex characteristics exist between male, female, and monoecious plants. Average fruit weight was the only parameter examined that was not useful as a secondary sex characteristic. Orthogonal contrasts examining plant height, vegetative biomass, and root biomass of plants were distinct from one another across the salinity gradient. Similarly, female and monoecious plants differed significantly from one another in terms of root biomass and the average mass: volume ratio of the fruit each sexual morph produced, as well as the proportion of smooth to wrinkled fruit produced. The data indicate that male, female, and monoecious plants are three distinct sexual morphs.     

PATTERNS OF BIOMASS ALLOCATION IN SPINACIA OLERACEA (CHENOPODIACEAE) ACROSS A SALINITY GRADIENT: EVIDENCE FOR A NICHE SEPARATION

Spinacia oleracea var. Americana was hydroponically grown across an experimental salinity gradient ranging from 0.0 to 6.0 grams NaCl/liter nutrient medium. Twenty male, 20 female, and 20 monoecious plants were randomly harvested from each treatment where possible. Root biomass (RTA), biomass allocated to leaves and stems (VA), and reproductive biomass (RA) were determined. Male, female, and monoecious plants were shown to have significantly different patterns of RTA, VA, and RA. Moreover, the treatments influenced allocation patterns of the sexes differently, i.e., a partial niche separation was observed among the sexes along the gradient with respect to RTA, VA, and RA. Additionaly, the sexes expressed different trade-offs between allocation of resources to the different tissues; most notably, under high salinity, RTA, and RA were strongly negatively correlated in females, but positively correlated in male and monoecious plants.     

LEAF OF SPINACIA OLERACEA (SPINACH): ULTRASTRUCTURE,AND PLASMODESMATAL DISTRIBUTION AND FREQUENCY,IN RELATION TO SIEVE-TUBE LOADING

Minor veins and contiguous tissues of the Spinacia oleracea leaf were analyzed by electron microscopy to determine the characteristics of the component cells and the structure, distribution, and frequency of plasmodesmata between the various cell types of the leaf. Mesophyll and bundle-sheath cells contain components typical of photosynthetic cells although the latter cell type contains smaller chloroplasts and fewer mitochondria and microbodies than the mesophyll cells. In addition, the mesophyll cells contain numerous invaginations of the plasmalemma bordering the chloroplasts and evaginations of the outer membrane of the opposing chloroplast envelope. In places, these membranes appear continuous with each other. The minor veins consist of tracheary elements, xylem parenchyma cells, sieve-tube members, companion and phloem parenchyma cells, and other cells simply designated vascular parenchyma cells. The companion and phloem parenchyma cells are typically larger than the sieve-tube members with the companion cells containing a much denser cytoplasm that the phloem parenchyma. Cytoplasmic connections occur along all possible routes from the mesophyll to the sieve-tube members and consist of either simple or branched plasmodesmata between parenchymatic elements or pore-plasmodesmata between the sieve-tube members and parenchyma cells. The highest frequency of plasmodesmata occurs between the sieve-tube members and companion cells, although the value is essentially the same as between the various parenchymatic elements of the phloem. Compared to several previously studied species, the frequency of plasmodesmata between cell types of the spinach leaf is low. These results are discussed in relation to apoplastic vs. symplastic solute transport and sieve-tube loading in this species.     

THE CHROMOSOMES OF SPLNACIA OLERACEA

Ellis , J. R., and Jules Janick . (Purdue U., Lafayette, Ind.) The chromosomes of Spinaeia oleracea. Amer. Jour. Bot. 47(3) : 210—214. Illus. 1960.—The somatic chromosomes of S. oleracea are described and each has been associated with one of the 6 morphological trisomics derived from triploid-diploid crosses. Of these 6 primary trisomies, reflex had been shown by genetic studies to be trisomic for the chromosomes carrying the sex-determining factors. This chromosome is the longest of the somatic complement and has a sub-median centromere. No obvious heteromorphism of this chromosome pair was observed in staminate plants. Heteromorphism involving this chromosome pair has been reported recently in 2 varieties of cultivated spinach by Zoschke (1956) and Dressier (1958) and was earlier reported by Araratjan (1939) for the wild species, S. tetandra. However, their accounts differ markedly from each other and with the present results in respect to the morphology of this chromosome pair. This study suggests the existence of races which differ with respect to the morphology of the chromosome pair containing the X Y factors.     

甘蓝热胁迫叶片细胞的超微结构研究

高温胁迫引起植物体损伤是很常见的,人们已从多方面探讨高温胁迫对植物的影响,主要工作集中在生理生化、膜结构、热激蛋白及作物产量等方面［１—４］,超微结构的变化也有少量报道［５—７］。但目前要建立一个高温对植物体影响的模式还比较困难。本文探讨了甘蓝不同耐热品种叶片细胞超微结构在热胁迫后的差异,目的是建立植物耐热程度的细胞学指标,为育种工作者选育耐热性品种提供细胞学依据。材料和方法试验材料为甘蓝（Ｂｒａｓｓｉｃａｏｌｅｒａｃｅａｖａｒ．ｃａｐｉｔａｔａＬ．）耐热品种“夏光甘蓝”和感热品种“京丰甘蓝”。…     

热胁迫下不结球白菜和甘蓝叶片组织结构的变化

利用显微及扫描电镜方法,研究不结球白菜及甘蓝的耐热品种和感热品种种在高温（３８－３９℃）胁迫下,叶片表皮和组织结构的差异。结果如下：耐热品种叶片下表皮比感热品种气孔频度高,气孔体积小且开张度小。耐热品种部分气孔呈关闭状态,而感热品种气孔基本上呈开放状态。显微结构观察到耐热品种叶肉组织细胞排列紧密,叶脉的维管束发达,特别是木质部的导管数量多且孔径大。而感热品种相比于耐热品种叶肉细胞排列疏松,维管束相