Dry matter content of apical and basal portions of Russet Burbank potatoes
Studies were made over a 4-year period of some factors affecting the dry matter content of the apical and basal portions of growing Russet Burbank potatoes. The greatest difference between portions was obtained from tubers of the normally irrigated plots of 1969. The amounts in the two portions in 1970 were nearly equal throughout the growing season. The major differences between the 2 years was a slightly cooler June and warmer maximum temperatures in July of the 1970 growing season. Moisture stress, particularly, early in the stage of tuber development (1972 season) caused a switch in amount of dry matter in the apical and; basal portions. Stress later in the development stage (1969 season) did not cause a switch. Fertility level was not as influential as moisture stress in affecting the ratio of dry matter in the two ends, whether under stress or normal moisture conditions.
Anatomy and compositional variations within potatoes III. Gross compositional gradients
The degree of compositional variations within potato tubers has been related to the development anatomy of the tuber and to exact tissues. The principal component, starch, shows differences in granule size distributions and in composition that appear when the young tuber averages about 1/300 of mature volumetric size. These differences pertain at maturity. When starch differences have been established, growth by cell divisions diminishes and growth by cell enlargement becomes dominant. In the mature tuber the general gradients for specific gravity, percent total solids, and percent total nitrogen decrease from stem end to bud end for cortical, perimedullary and pith tissues. Relationship between specific gravity and total solids is less parallel because differences in cell size and size of minute intercellular spaces also influence tissue density. Relationship between total solids and total nitrogen gradients from cortical tissue to pith were inverse with toal nirogen being higher in those tissues of lower total solids. These variations suggest need for new approaches in basic research on tuber quality improvement.ResumenEl grado de variaciones de la composición entre tubérculos de papa ha sido relacionado al desarrollo anatomico del tubérculo y a tejidos exactos. El componente principal, almidón, muestra diferencias en distribuciones de tamaño de gránulo y en la composición que aparecen cuando el volumen del tubérculo jóven tiene un promedio de 1/300 del volumen cuando maduro. Estas diferencias son pertinentes a la madurez. Cuando la diferencias en almidón hayan sidos establecidas, el crecimiento por division de células disminye y el crecimiento por agrandamiento de las células se hace dominante. En el tubérculo maduro el gradiente general de peso specifico, porcentaje de solidos totales, y el porcentaje de nitrogenos totales decrecn del punto del tallo (stem end) al punto apical (bud end) en los tejidos corticales, perimedulares y medula.La relación entre el peso específico y sólidos tales es menos paralelo porque laos diferencias en el tamaño de las celulas y el tamaño de los diminutos espacios intercelulares también influeyen en la densidad de tejidos. La relación entre gradientes de sólidos tolales y nitrógenos totales desde el tejido cortical a la médula fueron inversos para nitrógenes totales siendo mas altos en los tejidos de menor solidos totales. Estas variaciones indican la nececidad para nuevas metodas y ideas en las investigaciones básicas sobre el mejoramiento de la calidad del tubérculo.
Temperature effects on lily development rate and morphology from the visible bud stage until anthesis.
Day (DT) and night temperatures (NT) influenced Lilium longiflorum Thunb. 'Nellie White' stem elongation and development rate from the visible bud stage (VB) until anthesis. Plant height increase after VB was a function of the difference (DIF) between DT and NT (DT-NT). Plant height increased 90% as DIF increased from - 16 to 16C. A cubic model described bud development rate as a function of temperature from 14 to 30C. A linear model adequately described bud development rate as a function of average daily temperature from 14 to 21C. Based on the linear model, bud development rate increased 0.05 per day for each 1C increase in average daily temperature. The base temperature for bud development, i.e., the temperature at which bud development rate was 0, was calculated as 3.5C. Greenhouse forcing of vernalized Easter lilies is commonly divided into three phases: I) placement of vernalized bulbs in the greenhouse to flower initiation, II) flower initiation to VB, and III) VB to anthesis (De Hertogh and Wilkins, 1971). Plant morphological development differs during each of the forcing phases (De Hertogh and Wilkins, 1971). Growth during phase I is vegetative and consists of stem elongation and leaf expan- sion. Flower initiation, leaf expansion, and stem elongation oc- cur during phase II. Inflorescence expansion and stem elongation occur during phase III. Lily responses to temperature during phase III differed from those during phases I and II (Wang and Roberts, 1983). Lily development rate, quantified as days to unfold a leaf, is a de- creasing linear function of average daily temperature between 14 and 30C during phases I and II (Karlsson et al., 1988). Lily development rate during phase III is a nonlinear function of temperature (Healy and Wilkins, 1984). The effect of temper- ature on the rate of lily development decreases as DT and/or NT increase during phase III (Rob and Wilkins, 1973; Healy and Wilkins, 1984). Easter lily morphological development is thermomorpho- genie. For instance, internode length increases as the DIF be- tween DT and NT increases (Erwin et al., 1989). In addition, leaf orientation, leaf length, and flower length are also influ- enced by diurnal changes in temperature.