Martin C. Goffinet

A comparison of ‘Empire’ apple fruit size and anatomy in unthinned and hand-thinned trees

SummaryA stereological method was developed to analyze the anatomical features of fresh ‘Empire’ apple fruit sectors cut in the transverse equatorial plane. Fruits were from unthinned trees or trees hand-thinned to one fruit per cluster at –7, 0, 10, 20 or 40 d after full bloom. At final harvest (140 DAFB), fruits representing the size range within each treatment were analyzed for the effects of thinning on fruit size, weight and cortex anatomy, namely, parenchyma cell size, cell number and the proportion of cortex volume occupied by intercellular space (IS). A dissecting stereobinocular microscope fitted with a ten-by-ten reticule was used to count cells and proportion of IS in three fields in each of two cortex sectors per fruit. Cell volume in each field was derived by knowing only the grid area, a point-count for proportion of IS and a count of cell numbers within the grid. Fruit size and weight decreased as thinning was prolonged and unthinned trees had the smallest fruit. Within a thinning treatment...

An expolinear model of the growth pattern of the apple fruit

SummaryThe expolinear growth model of Goudriaan and Monteith (1990) is proposed as a new model for the inherent growth pattern of fruit of apple (Malus domestica Borkh.), defined as growth pattern under apparently non–limiting conditions This function has three parameters: maximum relative growth rate, maximum absolute growth rate, and “lost time” (x intercept of the linear growth phase). Apple fruit growth (weight basis) at very low crop loads and apparently optimum environmental conditions, displays an early positive curvilinear growth followed by linear growth to harvest, and is described well by the expolinear function. The model also fits growth patterns of ‘Empire’ and ‘Golden Delicious’ apple fruit differing in the rate of growth in the exponential phase due to differences in the crop load. Estimates of cortical cell numbers in ‘Empire’ fruit from related studies suggest that during the linear phase in mid–season, different growth rates among crop load treatments were apparently controlled by diffe...

Herbicidal Effects of Vinegar and a Clove Oil Product on Redroot Pigweed (Amaranthus retroflexus) and Velvetleaf (Abutilon theophrasti)

Abstract Weed management can be difficult and expensive in organic agricultural systems. Because of the potentially high cost of the natural product herbicides vinegar and clove oil, their efficacy with regard to weed species growth stages needs to be determined. A further objective was to identify anatomical and morphological features of redroot pigweed and velvetleaf that influence the effectiveness of vinegar and clove oil. Research was conducted on greenhouse-grown cotyledon, two-leaf, and four-leaf redroot pigweed and velvetleaf. Dose–response treatments for vinegar included 150-, 200-, 250-, and 300-grain vinegar at 318 L/ha and at 636 L/ha. Clove oil treatments included 1.7, 3.4, 5.1, and 6.8% (v/v) dilutions of a clove oil product in water (318 L/ha), and a 1.7% (v/v) dilution in 200-grain vinegar (318 L/ha). An untreated control was included. Separate plantings of velvetleaf and pigweed were treated with vinegar or clove oil and were used to study anatomical and morphological differences between the two species. Redroot pigweed was easier to control with both products than velvetleaf. Whereas 200-grain vinegar applied at 636 L/ha provided 100% control (6 d after treatment [DAT]) and mortality (9 DAT) of two-leaf redroot pigweed, this same treatment on two-leaf velvetleaf provided only 73% control and 18% mortality. The obtuse leaf blade angle in velvetleaf moved product away from the shoot tip, whereas in pigweed, the acute leaf blade angle, deep central leaf vein, and groove on the upper side of the leaf petiole facilitated product movement toward the stem axis and shoot tip. For both species, and at all application timings, 150-grain vinegar at 636 L/ha provided control equal to that of 300-grain vinegar at 318 L/ha. As growth stage advanced, control and biomass reduction decreased and survival increased. Application timing will be critical to maximizing weed control with vinegar and clove oil. Nomenclature: Vinegar, acetic acid; redroot pigweed, Amaranthus retroflexus L.; velvetleaf, Abutilon theophrasti Medic.

Semipermeable Layer in Seeds

Semipermeability may be defined as the ability of seed coverings to allow water uptake and gas exchange, while solute diffusion is restricted or prevented. The presence and location of a semipermeable layer was studied in seed coats of cabbage, leek, onion, tomato, and pepper. Morphological studies did not reveal a semipermeable layer in cabbage seed coats, and all subsequent research was performed on seeds of the other four species. Electron microscopy studies revealed that the semipermeable layer is located at the innermost layer of the seed coat just next to the endosperm. Ultrastructurally, the layer was similar for the four species, typically amorphous, highly compact, but easily distinguished from the remainder of the seed coat and endosperm tissue. The layer was permeable to water while inhibiting uptake of lanthanum salts. Histochemical analysis revealed that the semipermeable layer in seed coats of leek and onion was composed primarily of cutin, while in tomato and pepper the layer was composed of suberin.

Lamina Abortion in Terminal Bud-Scale Leaves of Populus deltoides during Dormancy Induction

Bud scales of terminal buds of Populus deltoides Bartr. ex Marsh. are formed by enlarged stipules. The laminae of the first bud-scale leaves mature and abscise, but the lamina of the last bud-scale leaf (or leaves) senesces prematurely and aborts. The immature lamina of the aborting leaf turns black, shrivels, and protrudes from the bud scales until physically dislodged during bud break the following spring. Senescence of the aborting bud-scale lamina begins with loss of starch and enlargement and vacuolation of cells abaxial to the dorsal bundle of the midrib at the lamina tip. These processes progress basipetally and laterally in the lamina, with degeneration becoming particularly evident in the spongy mesophyll. While lamina degeneration is under way, an abscission meristem begins to form distal to the stipules at the petiole base. Cell divisions initiating the abscission meristem are first evident in the reactivated adaxial meristem, and they spread laterally and obliquely across the petiole base. The vascular bundles are isolated by a funnel-shaped, protective layer of corklike cells that extends downward in the leaf base. The deteriorated central trace vasculature extends deeper in the leaf base than that of the lateral traces. We suggest that lamina senescence and abortion are in some way related to degeneration of the central leaf trace that forms the dorsal bundle of the midrib and petiole.

Cabbage (Brassica oleracea) Response to Pendimethalin Applied Posttransplant1

Field and greenhouse studies were conducted from 1997 to 2001 to determine cabbage response to posttransplant applications of pendimethalin (0.56 to 2.24 kg ai/ha). Differential variety response was minimal, and applications greater than 0.56 kg caused severe and persistent crop injury and reduced head number and yield in ‘Azan’, ‘Storage 4’, ‘Super Elite’, and ‘Super Red 90’. Pendimethalin (1.7 kg) applied posttransplant reduced cabbage yield weights 23, 30, and 87% with bare root, large, and small transplants, respectively. Application (0.84 kg) to soil, foliage, or soil and foliage caused 0, 81, and 82% dry weight reduction by 21 d after treatment, respectively. Anatomical analysis of two-leaf seedlings collected 3 wk after pendimethalin treatment (1.12 kg ai/ha) showed stunting of the shoot apical meristem and its emerging leaves, disorganization of apical structure with disruption of normal cell division and cell expansion, and abnormal differentiation of the vasculature in leaves and hypocotyls. Nomenclature: Pendimethalin; cabbage, Brassica oleracea L. Additional index words: Absorption, apical meristem, plant anatomy, transplant sensitivity, variety response. Abbreviations: DAT, days after treatment; POST, postemergence or posttransplant; PTR, pretransplant; WAT, weeks after treatment.

Polyethylene Glycol Embedment for Histological Studies of Bean Seed Testa of Low Moisture Content

Light microscopic examination of the structure of seed testa of snap and semihard bean seeds with 6% and 12% moisture contents in paraffin sections was unsuccessful because of poor paraffin infiltration and subsequent separation of subjacent and palisade cell layers. We devised an alternative method using polyethylene glycol (PEG) as the embedding material. Specimens were killed and fixed in the usual manner. They were then run up through a graded series (25, 50, 75, 100%) of PEG 1000 to PEG 1450, and finally embedded in a mixture of PEG 1450 and 4000 (19:1 by weight). Transverse and longitudinal sections retained excellent morphological detail and were suitable for histological study. Sections temporarily stained with 0.025% thionin allowed good quality photomicrographs.