VOA慢速英语2009年-Agriculture Report - Why Holding Fruit on

This is the VOA Special English Agriculture Report.

Alternate bearing is a widespread problem for growers of citrus and other fruit trees. It can affect a large area or just individual trees or even part of a tree. No, it is not a disease. Alternate bearing is when a tree produces a heavy crop one year, called an "on-crop," followed by an "off-crop" the next year.

On-crop trees produce a large number of small fruit with little value. Off-crop trees produce no fruit or a small number of large fruit that often have thick, unappealing skins.
　
Mandarin¹ trees heavy with fruit in an on-crop year

Citrus growers know that the number of fruit in their current crop has an inverse² effect on the number of flowers in the return bloom. In other words, if one number is big, the other number will be small.

Two researchers recently did a study to understand how this happens. Johannes Verreynne is now at Stellenbosch University in South Africa. Carol Lovatt is at the University of California, Riverside. They studied "Pixie" mandarin trees in the Ojai Valley of California. Mandarin oranges are also known as tangerines.

The study showed that fruit on the tree reduces the next bloom by stopping buds from appearing. This limits the number and length of summer and fall shoots. As a result, there is a reduction in the number of nodes, or joints³, that produce groups of flowers along stems. Fruit on the tree during spring bloom stops the growth of flowering shoots.

During an on-crop year, growers often treat the fruit so it can stay on the tree longer. The purpose is to extend the harvest season. Yet Carol Lovatt says holding fruit on the tree makes alternate bearing worse. The researchers advise growers to investigate the effects of thinning or pruning⁴ to reduce the number of fruit in early summer of the on-crop year.

The findings appeared in the Journal of the American Society for Horticultural Science.

Other kinds of trees that can experience alternate bearing include nut trees. Scientists recently studied the effects of mechanical thinning on two kinds of pecan trees in the southeastern United States. The results from the University of Georgia appeared in HortTechnology, also published by the society.

The study compared trees that had been thinned by machine with those that had not been thinned. The findings suggest that thinning during the on-crop year can increase the value of off-year pecan crops.

And that's the VOA Special English Agriculture Report, written by Jerilyn Watson. I'm Bob Doughty⁵.

1 Mandarin   

n.中国官话，国语，满清官吏；adj.华丽辞藻的

参考例句：

• Just over one billion people speak Mandarin as their native tongue.大约有十亿以上的人口以华语为母语。
• Mandarin will be the new official language of the European Union.普通话会变成欧盟新的官方语言。

2 inverse   

adj.相反的，倒转的，反转的；n.相反之物；v.倒转

参考例句：

• Evil is the inverse of good.恶是善的反面。
• When the direct approach failed he tried the inverse.当直接方法失败时，他尝试相反的做法。

3 joints   

接头( joint的名词复数 )； 关节； 公共场所（尤指价格低廉的饮食和娱乐场所） （非正式）； 一块烤肉 （英式英语）

参考例句：

• Expansion joints of various kinds are fitted on gas mains. 各种各样的伸缩接头被安装在煤气的总管道上了。
• Expansion joints of various kinds are fitted on steam pipes. 各种各样的伸缩接头被安装在蒸气管道上了。

4 pruning   

n.修枝，剪枝，修剪v.修剪（树木等）( prune的现在分词 )；精简某事物，除去某事物多余的部分

参考例句：

• In writing an essay one must do a lot of pruning. 写文章要下一番剪裁的工夫。 来自《现代汉英综合大词典》
• A sapling needs pruning, a child discipline. 小树要砍，小孩要管。 来自《现代汉英综合大词典》

5 doughty   

adj.勇猛的，坚强的

参考例句：

• Most of successful men have the characteristics of contumacy and doughty.绝大多数成功人士都有共同的特质：脾气倔强，性格刚强。
• The doughty old man battled his illness with fierce determination.坚强的老人用巨大毅力与疾病作斗争。