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مهندسی کشاورزی - باغبانی www.baghbani.ir - مطالب آبان 1387
 
مهندسی کشاورزی - باغبانی www.baghbani.ir
به اوج دل نشاندمت به خاستگاه زندگی / زمانه گر خزان شود تویی بهار زندگی
سه شنبه 14 آبان 1387 :: نویسنده : فنایی

ریشه درختان میوه

با جوانه زدن بذر , ابتدا ریشه چه ظاهر می شود  . این اندام بعد از رشد عمودی در خاک , ریشه اصلی یا ریشه راست را حاصل می کند . سپس در طول ریشه اصلی , ریشه های فرعی اولیه و از ریشه های فرعی اولیه به ترتیب ریشه های فرعی ثانویه حاصل می شود . منشاء ریشه های فرعی , معمولا قسمت دایره محیطیه ریشه اصلی می باشد . ریشه ها بر عکس اندام های هوایی گیاه فاقد کلروفیل و گره می باشند .

وسعت رشد عرضی ریشه ها معمولا در حدود سایه انداز درخت بوده اما عوامل دیگر همچون میزان رطوبت خاک , نوع بافت خاک , مواد غذایی خاک و نوع پایه می تواند در گسترش عرضی و عمقی ریشه تاثیر داشته باشد . رشد ریشه ها به دمای خاک نیز بستگی دارد و در طی زمستان اگر دمای خاک چند سانتی گراد بالاتر از صفر باشد به رشد خود ادامه خواهد داد .

ریشه های که به طور افقی در نزدیک سطح خاک رشد می کنند  معمولا به علت رسیدن اکسیژن کافی , فعال تر بوده و در جذب مواد غذایی نقش مهمی دارند . ریشه های که به صورت عمودی در عمق خاک قرار کی گیرند , اکثرا در جذب آب و برخی مواد کم مصرف نقش دارند . ریشه اصلی دارای ضخامت بیشتر بوده و به عمق بیشتری از خاک نفوذ می کند و چنانکه ذکر گردید از ریشه های اصلی ریشه های رعی منشاء می گیرند .ریشه های افشان در روی انشعابات سوم یا چهارم ریشه های فرعی قرار  می گیرند . این ریشه ها قطر مساوی داشته و طول آنها کمتر است . اکثرا تار های کشنده روی ریشه های افشان قرار می گیرند . تار های کشند در نوک ریشه های جوان و کمی بالاتر از کلاهک ریشه قرار می گیرند و از تک سلول های کشیده و طویل که دارای واکوئل بزرگ هستند , به وجود می آیند . تار های کشنده زایده های اپیدرمی بشمار می آیند و عمر آنها محدود می باشد این تار ها منطقه وسیع جذب آب و مواد غذایی را حاصل می کنند .

 

سیستم گسترش درختان میوه در خاک به رشد و گسترش ریشه های فرعی اولیه بستگی دارد و به طور کلی به سه گروه سیستم عمیق , نیمه عمیق  و سطحی تقسیم می شود معمولا ریشه های سیب , گوجه , به , زیتون , گلابی و هلو  تا عمق 1.5 الی 2 متتری خاک , ریشه های زرد آلو , بادام  و گرد تا عمق 2 الی 3 متری خاک گسترش می یابند . در ضمن ریشه ها به اکسیژن کافی نیاز دارند که باید در اختیار آنها قرار گیرد . در خاک هایی که بافت سبک دارند, ریشه ها تنفس کافی انجام می دهند . در خاک های سنگین  و یا در خا کها یی که زهکشی کافی نداشته باشند , ریشه ها با کمبود اکسیژن روبرو خواهند شد . ریشه برخی از درختان میوه از جمله هلو , گیلاس , زرد آلو , بادام  و مرکبات به کمبود اکسیژن حساسند . 

 

 





نوع مطلب : گیاهشناسی ـ بحث ریشه، 
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دوشنبه 6 آبان 1387 :: نویسنده : فنایی

معرفی درخت زیتون                                     OLIVE

B/W sketch

Olea europaea L.

Oleaceae

Common Name: Olive.

Related Species: Wild Olive (Olea africana), Oleaster (O. europaea var. oleaster).

Distant Affinity: American Olive (Osmanthus americana), Fragrant Olive (O. fragrans).

Origin: The olive is native to the Mediterranean region, tropical and central Asia and various parts of Africa. The olive has a history almost as long as that of Western civilization, its development being one of civilized man's first accomplishments. At a site in Spain, carbon-dating has shown olive seed found there to be eight thousand years old. O. europaea may have been cultivated independently in two places, Crete and Syria. Archeological evidence suggest that olives were being grown in Crete as long ago as 2,500 B.C. From Crete and Syria olives spread to Greece, Rome and other parts of the Mediterranean area. Olives are also grown commercially in California, Australia and South Africa. There is some disagreement over when the trees first appeared in California. Some say they were introduced in 1769 when seeds brought from Mexico were planted. Others site the date 1785 when trees were brought in to make olive oil.

Adaptation: The olive requires a long, hot growing season to properly ripen the fruit, no late spring frosts to kill the blossoms and sufficient winter chill to insure fruit set. Home grown olives generally fruit satisfactorily in the warmer coastal valleys of California. Virtually all U.S. commercial olive production is concentrated in California's Central Valley, with a small pocket of olive acreage outside Phoenix. The tree may be grown as an ornamental where winter temperatures do not drop below 12° F. Green fruit is damaged at about 28°, but ripe fruit will withstand somewhat lower temperatures. Hot, dry winds may be harmful during the period when the flowers are open and the young fruits are setting. The trees survive and fruit well even with considerable neglect. Olives can also be grown in a large container, and has even appeared in shows as a bonsai.

DESCRIPTION

Growth Habits: The olive is an evergreen tree growing to 50 ft. in height with a spread of about 30 ft. The tree can be kept to about 20 ft. with regular pruning. The graceful, billowing appearance of the olive tree can be rather attractive. In an all-green garden its grayish foliage serves as an interesting accent. The attractive, gnarled branching pattern is also quite distinctive. Olives are long-lived with a life expectancy of 500 years. The trees are also tenacious, easily sprouting back even when chopped to the ground.

Foliage: The olive's feather-shaped leaves grow opposite one another. Their skin is rich in tannin, giving the mature leaf its gray-green appearance. The leaves are replaced every two or three years, leaf-fall usually occurring at the same time new growth appears in the spring.

Flowers: The small, fragrant, cream-colored olive flowers are largely hidden by the evergreen leaves and grow on a long stem arising from the leaf axils. The olive produces two kinds of flowers: a perfect flower containing both male and female parts, and a staminate flower with stamens only. The flowers are largely wind pollinated with most olive varieties being self-pollinating, although fruit set is usually improved by cross pollination with other varieties. There are self-incompatible varieties that do not set fruit without other varieties nearby, and there are varieties that are incompatible with certain others. Incompatibility can also occur for environmental reasons such as high temperatures.

Fruit: The olive fruit is a green drupe, becoming generally blackish-purple when fully ripe. A few varieties are green when ripe and some turn a shade of copper brown. The cultivars vary considerably in size, shape, oil-content and flavor. The shapes range from almost round to oval or elongated with pointed ends. Raw olives contain an alkaloid that makes them bitter and unpalatable. A few varieties are sweet enough to be eaten after sun drying. Thinning the crop will give larger fruit size. This should be done as soon as possible after fruit set. Thin until remaining fruit average about 2 or 3 per foot of twig. The trees reach bearing age in about 4 years..



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دوشنبه 6 آبان 1387 :: نویسنده : فنایی

KIWIFRUIT

B/W sketch

Actinidia deliciosa

Actinidiaceae

Common Names: Kiwifruit, kiwi, Chinese gooseberry, Yang-tao.

Related species: Hardy Kiwi (Actinidia arguta, A. kolomikta), Chinese Egg Gooseberry (A. coriacea), Red Kiwi (A. melanandra), Silver Vine (A. polygama), Purple Kiwi (A. purpurea).

Origin: The kiwifruit is native to the Yangtze River valley of northern China and Zhejiang Province on the coast of eastern China. The first seeds were brought out of China by missionaries to New Zealand at the turn of this century. Early nurserymen in New Zealand, such as Alexander Allison, Bruno Just, and Hayward Wright, recognized the potential of the fruit and it soon became a popular backyard vine. Several plants were sent to the Chico Plant Introduction Station in California and exist to this date. In addition to New Zealand and California, kiwifruit is also grown commercially in such areas as Italy, South Africa and Chile.

Adaptation: The plants need a long growing season (at least 240 frost-free days) which will not be hampered by late winter or early autumn freezes. When fully dormant they can withstand temperatures to about 10° F (and perhaps a bit lower.) However they must acclimate to cold slowly and any sudden plunge in temperature may cause trunk splitting and subsequent damage to the vine. Late winter freezing temperatures will kill any exposed buds which limits the adaptable growing areas of kiwifruit. In California the kiwifruit is an appropriate crop wherever citrus fruits, peaches and almonds are successful. All cultivars need a certain period of winter chilling and their needs vary dramatically, dependent upon cultivar. The most popular cultivar, Hayward, does best with a winter rest of 800 hours of chilling (defined as total hours between 32° and 45° F.) For warm winter areas with low chill hours (such as southern California, southern Texas, and Florida), cultivars such as Elmwood, Dexter, Abbott, or Vincent would be more suitable. In very mild winter areas the vines may retain their leaves and fail to flower the following season. Kiwi vines can be successfully grown in large containers.

DESCRIPTION

Growth Habit: In the forests where it is native, the plant is a vigorous, woody, twining vine (liana) or climbing shrub. It is not unusual for a healthy vine to cover an area 10 to 15 feet wide, 18 to 24 feet long and 9 to 12 feet high. In cultivation it is supported on a trellising system.

Foliage: The large, deep green, leathery leaves are oval to nearly circular and 7 to 10 inches in diameter. Young leaves and shoots are coated with red hairs, while mature leaves are dark green and hairless on the upper surface, downy-white with prominent, light colored veins beneath.

Flowers: The large (1 to 2 inch diameter), white to cream colored flowers are somewhat fragrant and produced as singlets to triplets in the leaf axiles. The flowering period extends over several weeks from early May to June, depending on climatic conditions. The plants are dioecious, bearing either male or female flowers, thus needing plants of both sexes to produce fruit. Self-fruiting males are known to exist but produce less desirable fruit.

Fruit: The oval, ovoid or oblong fruit is up to 2-1/2 inches long, with russet-brown skin densely covered with short, stiff brown hairs. The flesh, firm until fully ripe, is glistening, bright green or sometimes yellow, brownish or off-white, except for the white, succulent center from which radiate many fine, pale lines. Between these lines are scattered minute dark-purple or nearly black seeds, unnoticeable in eating. The flavor is sweet/tart to acid, somewhat like that of the gooseberry with a suggestion of strawberry.

on the kiwifruit



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