Nutrient medium can be sterilized using a household-type microwave oven. The required microwave treatment time was influenced by the oven's microwave power intensity (70 to 700 W), vessel type, volume of medium employed, and the presence of energy sink water reservoirs (ESWR). Growth rates of strawberry (Fragaria vesca L.) shootlets, lemon [Citrus limon (L.) Burm. f.] fruit halves, or carrot (Daucus carota L.) callus cultured on either microwaved or autoclaved media were similar. Microwaving and autoclaving appeared to reduce GA3 activity compared with medium containing filter sterilized GA3. Chemical name used: gibberellic acid (GA3).

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A comparative growth study was conducted on juice vesicles cultured in the form of various fruit explant types (equatorially bissected fruit halves, longitudinally bissected fruit halves, one‐eighth sections of fruit, one‐quarter sections of fruit, whole carpel segments, 2 or 3 mm thick equatorial slices of fruit, and 1 cm2 fruit endocarp pieces) from 15 mm diam Citrus limon (L.) Burm. f. cv. Eureka lemons. Juice vesicles within equatorial fruit halves produced the least amount of callus. Furthermore, these juice vesicles grew similarly to juice vesicles occurring in the tree grown fruit. A study of cultured equatorial fruit halves using 10–45 mm diam lemons was then conducted. Fruit half cultures containing juice vesicles could be readily established from 15–45 mm diam lemons. Vesicles from 10 mm diam fruit halves, however, invariably produced callus. Vesicles cultured within fruit halves produced proportionately less callus as their fruit diam increased. Juice vesicles cultured in 15–30 mm diam fruits lost their original green color and turned opaque as they matured (i.e., after 3–6 months in culture). A method is also presented, whereby whole lemon fruits can be established and maintained in vitro. Lemons, 35–45 mm in diam, were the best explant sources for establishing whole fruit cultures. Juice vesicles in whole fruit cultures may remain viable for up to 8 months in culture.

Juice vesicles in several Citrus species and cultivars differentiate additional vesicle apex primordia. Four distinct types of juice vesicles were described and quantified in citrus fruits: solitary (single stalk/single vesicle body/single apex primordium), dual-tipped (single stalk/single vesicle body/dual apex primordia), multiple-tipped (single stalk/single vesicle body/multiple apex primordia) and branched (single-stalk/multiple vesicle bodies/multiple apex primordia). The type and frequency of branching varies considerably among species and within cultivars. Branching was found in grapefruit, mandarin, pummelo, and tangelo, but not in blood orange, citron, lemon, lime, navel orange, rough lemon, sour orange, sweet orange, Valencia orange, and several other species. ‘Kao Panne’ pummelo [Citrus maxima (J. Burman) Merrill] exhibited one of the highest rates of vesicle branching, with 72% of its vesicles exhibiting this condition. The average number of branching vesicles produced per stalk was 3.7 for this cultivar. The frequency of branching was below 50% in other branched groups (e.g., grapefruit, mandarin, and tangelo).