应《网络安全法》要求，自2017年10月1日起，未进行实名认证将不得使用互联网跟帖服务。为保障您的帐号能够正常使用，请尽快对帐号进行手机号验证，感谢您的理解与支持！

24小时热门版块排行榜    

小木虫论坛-学术科研互动平台 » 生物医药区 » 动植物 » 综合其他 » VPD的概念
31/1返回列表
查看: 3449  |  回复: 2
只看楼主 @他人 存档 新回复提醒 (忽略) 收藏    在APP中查看

lidongxiao

木虫 (正式写手)

[交流] VPD的概念

各位大侠：
VPD代表饱和蒸汽压差，光合仪测得的VPD和大气VPD一样吗？有什么区别？非常感谢
回复此楼

» 猜你喜欢

» 抢金币啦！回帖就可以得到:

查看全部散金贴
1楼 2013-04-12 22:58:26
已阅   回复此楼   关注TA 给TA发消息 送TA红花 TA的回帖

haozixiaozhu

木虫 (小有名气)
★
小木虫: 金币+0.5, 给个红包，谢谢回帖
Vapor Pressure Deficit (VPD) can be defined as the difference (or deficit) between the pressure exerted by water vapor that could be held in saturated air (100% RH) and the pressure exerted by the water vapor that is actually held in the air being measured. From a plant’s perspective the VPD is the difference between the vapor pressure inside the leaf compared to the vapor pressure of the air. The only problem with leaf-to-air VPD is it’s difficult to determine accurately because you need to know the leaf temperature. The most practical approach that most environmental control companies use to assess VPD is to take measurements of air temperature within the crop canopy. A well positioned sensor measuring the air temperature and humidity close to, or just below, the crop canopy is adequate for providing a good indication of actual leaf conditions.
       VPD is essentially a combination of temperature and relative humidity in a single value. VPD values run in the opposite way to RH vales, so when RH is high VPD is low. The higher the VPD value, the greater the potential the air has for sucking moisture out of the plant.
     
       Computing VPD
        Saturation Vapor Pressure (es, kPa) =0.6108 * exp(17.27 * T / (T + 237.3)), where T is the air temperature
        Actual Vapor Pressure (ea, kPa) =RH / 100 * es, where RH is the relative humidity(%)
        VPD(kPa)=es - ea
        Vapor pressure inside the leaf(es,lesf, kPa) =0.6108 * exp(17.27 * T / (T + 237.3)), where T is the leaf or canopy temperature
        leaf-to-air VPD(kPa)=es,leaf - ea
赞一下 回复此楼
2楼2013-04-14 08:29:06
已阅   回复此楼   关注TA 给TA发消息 送TA红花 TA的回帖

lukia

金虫 (正式写手)
★
小木虫: 金币+0.5, 给个红包，谢谢回帖
引用回帖:
2楼: Originally posted by haozixiaozhu at 2013-04-14 08:29:06
Vapor Pressure Deficit (VPD) can be defined as the difference (or deficit) between the pressure exerted by water vapor that could be held in saturated air (100% RH) and the pressure exerted by the wa ...

弱弱的问一句，有中文版的么？.....请原谅我的无耻....
赞一下 回复此楼
3楼2013-04-14 08:57:54
已阅   回复此楼   关注TA 给TA发消息 送TA红花 TA的回帖
相关版块跳转 我要订阅楼主 lidongxiao 的主题更新
31/1返回列表
普通表情 龙 兔 虎 猫 高级回复 (可上传附件)
信息提示
关闭
请填处理意见
关闭