In leaves, the upregulated and downregulated SlARF6A transgenic lines possessed higher and lower chlorophyll levels, respectively, than the WT plants . Then, chlorophyll autofluorescence in the pericarp was detected using confocal laser scanning microscopy. OE-SlARF6A plants had stronger chlorophyll auto- fluorescence, while the RNAi-SlARF6A lines had weaker chlorophyll autofluorescence in both epicarp and endocarp tissues compared with that of the WT plants . Then, the chloroplasts were observed using a transmission electron microscope . The growth of individual chloroplasts in OE-SlARF6A fruits was obviously promoted, with a significant increase in size and length . However, the number of chloroplasts per cell in OE-SlARF6A fruits was the same as that in the WT plants. For the RNAi-SlARF6A lines, the number of chloroplasts per cell was obviously decreased, but the size of individual chloroplasts was not changed .The name stone fruit refers to the stone-like pit encasing the seed. It is the soft, flavorful, juicy, aromatic , mouthwatering combination of sugars and acids in fleeting succession that intrigues us as gardeners. The true “raison d’etre” for these swollen ovary walls is merely to attract animals to eat them and disperse the seed to perpetuate the species. After much field testing and reflection, I would say of this evolutionary strategy — Well done, well done indeed! The stone fruits are nonclimacteric fruits. Climacteric derives from the Greek root meaning “critical point,” or literally, “rung of a ladder.” It is therefore a major turning point or critical stage — in this case, pre-senescence or death. Climacteric fruits such as apples and pears, bananas, kiwis, weed drying room and avocados can be picked mature but green, held under refrigeration, and will ripen and color on their own, or with the introduction of ethylene gas.
These fruits store their sugars in the form of starches that are converted back to sugars by enzymes and by warm temperatures off the tree. Nonclimacteric stone fruits don’t produce or respond to ethylene gas. They ripen gradually, and don’t store sugar as starch, but instead depend on their continued connection—via the conductive vascular tissue of the stem—to the parent for continued sweetening. They get no sweeter off the tree, though enzymes may promote their softening. Thus the quality of the fruit is dependent on the ripening that takes place on the tree. In fact, cold storage retards natural pectin breakdown, causing stone fruits to become dry and mealy.Peaches and nectarines hail from northwestern China . The specific name persica is a misnomer, probably attributed to its spread via trade caravans from China into Iraq and Iran and eventually to Europe. The fruit came to the Americas with the Spanish explorers in the 16th century on their conquering expeditions. It was then spread across the U.S. by Native Americans. The nectarine is genetically identical to the peach but with a recessive gene for pubescence . The nectarine is as old as the peach, with records of cultivation dating back to 2,000 BC. It is either a chance seedling or a whole tree mutation . Commercially, peaches and nectarines are grown at latitudes between 25º–45º North and South of the equator. Major peach growing regions include Chile, China, Northern Italy, Spain, Turkey, California, Southeastern U.S., New York, Pennsylvania, and Michigan. They can be grown closer to the equator than any other species of temperate zone deciduous fruits because of their tolerance for heat and humidity, and their low chill requirements for breaking dormancy. The peach, often referred to in old pomology texts as the “Queen of Fruits,” ranks only behind the apple in worldwide production and economic worth. Their sweet flavor, aroma, and nectar set the bar very high for sun-warmed tree-ripe perfection that evokes the essence of summer.
Peaches are the shortest-lived of all deciduous fruit trees, with an average life expectancy of only 20–40 years . Because the genetics of the peach are much less variable than any other fruit, the trees of almost every seedling bear edible fruit. There are also more cultivars of peaches than any other fruit owing to the ease of obtaining quality seedlings from peach crosses. Peaches and nectarines can be grouped into two basic flesh types—clingstone and freestone. Clingstones exhibit a firm-textured flesh that cannot be pulled off the stone and must be cut away with a knife. Because they hold their shape when cut or sliced, they are the logical candidates for canning, drying, or being used fresh, halved, or sliced. Freestones are softer-fleshed varieties with higher juice content, and separate easily from the pit. They lend themselves to fresh eating.Additionally, peach tastes can be linked to flesh color and “old school” vs. “new school” varieties. Old school varieties don’t color evenly or have as bright a sheen to their skin. They have a more balanced sugar/acid ratio contributing to a fuller old-timey peach flavor. They have a very limited shelf life, must be tree ripened to have full flavor, and bruise easily, giving rise to that old farmers’ market adage, “Real peaches don’t stack.” These “old school” varieties include Suncrest, Elberta, Babcock, J.H. Hale, Red Haven, Le Grand, Rio Oso, Sun Grand, and Baby Crawford . Because they are more difficult to grow they’re considered all but obsolete in today’s produce world. And because the fruit deteriorates rapidly in cold storage, the older varieties are a mere remembrance fading in the rear view mirror—a tribute to a time when there was a fierce loyalty to varietal brand names. New school peach and nectarine varieties are all sugar and sweetness with very little acid. They have a rich pink/red hue to their skin, are firm fleshed, larger on average than the old varieties, and continue to ripen off the tree under refrigeration. They have a sublime, delicate flavor that is less peachy and more sugary. New school varieties include Arctic Supreme, Arctic Glo, White Lady, Sugar Lady, Snow Giant, and Arctic Jay . In general , white-fleshed varieties are sweeter than the more sugar/acid balanced, aromatic, yellow-fleshed varieties. A separate category of peaches, including Peento, Donut, Saturn or Bagel peaches , are synonyms for the smallest, sweetest, melting-fleshed peaches native to China. They are flat, small , and shaped like their name implies. They have a very short season and bruise more easily than any other type of peach.The peach is a vigorous upright grower in the early years after planting. As it matures the tree’s habit morphs to a more naturally spreading form with moderate to weak vigor. Peach leaves cast dense shade, so it is important to train trees to allow sunlight to penetrate into the center of the tree. Remember, sunlight translates to color and emphatically to high sugar content. The largest, best-quality peaches are produced on lateral one-year-old branches that hang on young, actively growing main scaffold branches . With peaches, drying rack for weed what you grew last year is what you’re eating this year. That is to say that a lateral branch will grow one year and simultaneously produce and express fruit buds. In year two these branches bear fruit. They should be shortened to 12–18 inches long and fruit should be thinned to 6–8 inches apart. Because peach fruit buds contain only a solitary flower, they set a single fruit and unlike apples don’t need cluster thinning. Proper thinning equals proper size and is especially critical on small-fruited varieties like Saturn types, Baby Crawford, and all nectarines . In the third year, the lateral shoot will die out and not bear any fruit.
Or it will grow new wood that bears the following year, but is too far away from the main branch for either good mechanical support or continued flow of nutrients for size and taste. In any given winter pruning session, approximately one half the laterals should be stubbed to 1–3 buds or 1–3 inches to renew growth and bear the following year. Similarly, after laterals have fruited they should be stubbed back to renew the cycle. Since new growth is prioritized on peaches and nectarines, primary branches are pruned hard annually in the winter to encourage good extension growth and the induction of laterals. As a result, it is not unusual to prune 40–60% of the previous year’s total growth off a peach or nectarine . Additionally the primary scaffold branches on an peach are completely renewed by stubbing them to their base every 5–7 years. This re-scaffolding is best achieved incrementally over a 3–5 year period. More markedly than with pome fruits, peaches slow down and lose vegetative vigor with age. Almost all peach/nectarine varieties are self fruitful, that is they accept pollen from their own flowers and do not need pollen from another variety to set fruit. Notable exceptions are Elberta types and Hale cultivars. Peach leaf curl is a leaf fungus that afflicts almost all peach and nectarine varieties in almost all growing regions. It is especially devastating in cool, coastal climates where trees can be completely defoliated in June during a bad year. Peach leaf curl infects the leaves and young shoots. It causes distorted, reddened, puckererd foliage and when severe can radically reduce annual production and deinvigorate the tree over the long term. As with most pest and disease populations, the aim in controlling peach leaf curl is to aggressively prevent high spore pressure. It is difficult to work backward from high pressure to good control organically. An easy-to-remember schedule aligns with three big American holidays: Thanksgiving , Christmas and of course the Super Bowl . Resistant peach varieties include Frost, Avalon Pride, Mary Jane, and Q1- 8. Extremely susceptible but great tasting varieties include Babcock, Elberta, and the Saturn types.Compared to pome fruits, rootstock options are more limited with stone fruits. There are no truly dwarf stocks—the only choices are full-size and semi-dwarf. The principle attributes imparted to fruit trees via rootstocks are size control, disease/pest resistance, and fruiting efficiency. Size Control – Full-size or standard stocks produce vigorous vegetative growth . Trees on these stocks will top out at 20–30 feet tall. Semi-dwarfing stocks reduce tree size . Pest, Disease Resistance – The main issue with stone fruits is root susceptibility to nematodes , which are multicellular, microscopic non-segmented roundworms. Nematodes sap tree roots of nutrients, reduce vigor, and lower fruit productivity. The rootstocks Nemaguard and Nemared impart resistance, especially with peaches and nectarines. Fruiting Efficiency – Although not as dramatic as with pome fruits, stone fruit dwarfing rootstocks promote greater fruit production per area of tree canopy. The mechanisms for this are not fully understood, but the result is demonstrable.These are the plums of choice throughout Europe, more widely planted than apples and pears. In the Slavic countries Domestica plums exceed 50% of all acreage planted to fruit trees. There is evidence of Domestica plums being grown in Europe prior to 2,000 years ago. Commonly dubbed prune plums in the U.S., European plums offer a more diverse spectrum of colors, shapes, sizes, tastes, and uses than any other fruit. The fruit is small and oval-oblong—almost egg shaped. Skin colors are in the blue-purple range for prune types to yellow, orange, and red for dessert types. They thrive in areas with moderate summers , low humidity and moderate winter chill. Major production areas worldwide include Western U.S., New York state, Italy, Chile, Turkey, Romania, Yugoslavia, France, Austria, and Germany. The trees of European plums are upright and vigorous when young and develop a pendant weeping form and weak vigor when established. At 50–80 years they are fairly long-lived. The fruit buds are the longest lived of the stone fruits , so minimal renewal pruning is necessary. They tend to be a shorter tree than Japanese plums . European plums also have a higher chill requirement to bloom and set fruit and bloom later than their P. salicina counterparts, and in some years avoid the pollination problems caused by erratic spring weather and rain. They are self unfruitful and thus need pollen from another variety to set fruit. The varieties Santa Rosa and Wickson are universal pollinators. European plums are smaller and firm textured, with less juice than Japanese plums. They are also free stone. Because of their high sugar content they dry readily as prune plums. Fresh off the tree, European plums are a high quality dessert fruit and because of their low juice content and freestone nature, are excellent candidates for cooking in tarts and other recipes.This species, known as the gage plums, originated in Turkey and was brought to Mediterranean Europe by the Romans.